Fruit and Vegetables: Harvesting, Handling and Storage

By Anthony Keith Thompson

Completely revised, updated and enlarged, now encompassing two volumes, this third edition of Fruit and Vegetables reviews and evaluates, in comprehensive detail, postharvest aspects of a very wide international range of fresh fruit and vegetables as it applies to their physiology, quality, technology, harvest maturity determination, harvesting methods, packaging, postharvest treatments, controlled atmosphere storage, ripening and transportation.

The new edition of this definitive work, which contains many full colour photographs, and details of species not covered in the previous editions, provides key practical and commercially-oriented information of great use in helping to ensure that fresh fruit and vegetables reach the retailer in optimum condition, with the minimum of deterioration and spoilage.

With the constantly increasing experimental work throughout the world the book incorporates salient advances in the context of current work, as well as that dating back over a century, to give options to the reader to choose what is most relevant to their situation and needs. This is important because recommendations in the literature are often conflicting; part of the evaluation of the published results and reviews is to guide the reader to make suitable choices through discussion of the reasons for diverse recommendations. Also included is much more on the nutritional values of fruit and vegetables, and how these may vary and change postharvest. There is also additional information on the origin, domestication and taxonomy of fruit and vegetables, putting recommendations in context.

Fruits and Vegetables 3e is essential reading for fruit and vegetable technologists, food scientists and food technologists, agricultural scientists, commercial growers, shippers, packhouse operatives and personnel within packaging companies. Researchers and upper level students in food science, food technology, plant and agricultural sciences will find a great deal of use within this popular book. All libraries in research establishments and universities where these subjects are studied and taught should have copies readily available for users.

• Language: English
• Publisher: Wiley
• Release date: Oct 3, 2014
• ISBN: 9781118654019

Book preview

Table of Contents

Cover

Dedication

Title Page

Copyright

About the Author

Preface

Acknowledgements

Chapter 1: Preharvest factors on postharvest life

Nutrients

Soil acidity

Organic production

Light

Day length

Temperature

Water relations

Production system

Harvest maturity

Preharvest infection

Growth regulation

Chapter 2: Assessment of crop maturity

Field methods

Postharvest methods

Chapter 3: Harvesting and handling methods

Crop damage

Harvesting

Field transport

Chapter 4: Precooling

Heat removal

Precooling methods

Chapter 5: Packaging

Types of packaging

Package recycling

Modified atmosphere packaging

Chapter 6: Postharvest treatments

Minerals

Astringency removal

Antioxidants

Sprout suppressants

Fruit coatings

1-MCP

Salicylic acid

Curing

Hot water treatment

Vapour heat treatment

Degreening

Chapter 7: Storage

Store management and organisation

Store design and method

Refrigerated storage

Controlled atmosphere stores

Hypobaric storage

Chapter 8: Diseases and pests

Pests

Diseases

Legislation

Mode of infection

Non-chemical methods of disease control

Chapter 9: Safety

Micotoxins

Bacterial toxins

Safety in controlled atmosphere stores

Toxicity of packaging material

Packhouse safety

Chapter 10: Marketing and transport

Marketing

Marketing systems

Market analysis

Branding

National transport

International trade

Cold chain

Transport by sea

International transport by airfreight

Temperature monitoring

Chapter 11: Fruit ripening

Changes during fruit ripening

Controlled atmosphere storage on ripening

Design of ripening rooms

Ethylene on ripening

Chapter 12: Specific recommendations for fruit

Abiu

Abiyuch

Açaí

Acerola

Achachairú

African fan palm

African pear

Amelanchier

Apricot

Arbutus

Asian pears

Assyrian plum

Atemoya

Arazá

Babaco

Bael

Bakuri

Bakupari

Banana

Banana passionfruit

Baobab

Bayberry

Bilimbi

Biriba

Bitter melon

Blackberry

Blackcurrant

Black sapote

Blueberry, bilberry

Camu-camu

Canistel

Capulin

Carambola

Carissa

Cashew apples

Cherimoyas

Cherry

Chinese jujube

Chinese squash

Chinese white pear

Citron

Citrus hybrids

Clementines

Cloudberries

Cocona

Cranberries

Custard apple

Dabai

Damsons

Dates

Dewberries

Dragon fruit

Durian

Easy peeling citrus fruits

Elderberry

Emblic

Feijoas

French sorrel

Garden huckleberry

Genips

Giant granadilla

Ginseng

Gooseberry

Governor's plum

Green gages

Grapes

Grapefruit

Guava

Gulupa

Hawthorne

Hog plum

Huckleberry

Ilama

Indian jujube

Jackfruit

Jamun

Jamaican honeysuckle

Jamaican sorrel

Japanese plum

Jostaberry

Kiwano

Kiwifruit

Kinnow

Kumquats

Langsat, lanzon, duku

Lemons

Lime berry

Limes

Limequats

Litchi

Loganberries

Longan

Longkong

Loofah

Loquat

Malay apple

Mamey

Mandarin

Mango

Mangosteen

Medlar

Melon

Monstera

Mora

Mountain damson

Mulberry

Mume

Nance

Naranjilla

Nectarines

Noni

Ōhelo berry

Olives

Orange

Otahiete apple

Palmyra palm

Paniala

Papaya

Papayuela

Passionfruit

Peaches

Pear

Pejibaye

Physalis

Pineapple

Pitanga

Plum

Pomegranate

Pond apple

Prickly pear

Pomelo

Quince

Rambutan

Raspberry

Redcurrant, whitecurrant

Red huckleberry

Red whortleberry

Rhubarb

Rose apple

Rowal

Salak

Sansapote

Santol

Sapodillas

Sapote

Sapote mamey

Satsuma

Seville orange

Shea butter tree

Sloe

Soncoya

Sour cherry

Soursop

Spanish plum

Star apple

Strawberry

Strawberry guava

Sudachi

Sugar cane

Sweet calabash

Sweet granadilla

Sweet passionfruit

Sweetsop

Tangerines

Tayberries

Watermelon

Wax apple

West Indian gooseberry

White sapote

Wild cucumber

Worcester berries

Yard-long bean

Zapotes chupa chupa

References

Index

List of Illustrations

Figure 1

Figure 2

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Figure 123

List of Tables

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

Table 7

Table 8

Table 9

Table 10

Table 11

Table 12

Table 13

Table 14

Table 15

Table 16

Table 17

Table 18

Table 19

Table 20

Table 21

Table 22

Table 23

Table 24

Table 25

Table 26

Table 27

Table 28

Table 29

Table 30

Table 31

Table 32

Table 33

Table 34

Table 37

Table 38

Table 39

Table 40

Table 41

Table 42

Table 43

Table 44

Table 45

Table 46

Table 47

Table 48

Table 53

Table 54

Table 55

Table 56

Table 57

Table 58

Table 59

Table 60

Table 61

Table 62

Table 63

Table 75

Table 64

Table 65

Table 66

Table 67

Table 68

Table 69

Table 70

Table 71

Table 72

Table 73

Table 74

Table 76

Table 77

Table 78

Table 79

Table 80

Table 81

Table 82

Table 83

Table 84

Table 85

Table 86

Table 87

Table 88

Table 89

Table 90

Table 91

Table 92

Table 93

Table 94

Table 95

Table 96

Table 98

Table 99

Table 100

Table 101

Table 102

Table 103

Table 104

Table 105

Table 106

Table 107

Table 108

Table 109

Table 110

Table 111

Table 112

Table 114

Table 113

Table 115

Table 116

Table 117

Table 118

Table 119

Table 120

Table 121

Table 122

Table 123

Table 124

Table 125

Table 126

Table 127

Table 128

Table 129

Table 130

Table 133

Table 134

Table 135

Table 136

Table 137

Table 138

Table 139

Table 140

Table 141

Table 142

Table 143

Table 144

Table 145

Table 146

Table 147

Table 148

Table 149

Table 150

Table 151

Table 152

Table 153

Table 154

Table 155

Table 156

Table 157

Table 158

Table 159

Table 160

Table 162

Table 163

Table 164

Table 165

Table 166

Table 167

Table 168

Table 169

Table 170

Table 171

Table 172

Table 173

Table 174

Table 175

Table 176

Table 177

Table 178

Table 179

Table 180

Table 181

Table 182

Table 183

Table 184

Table 185

Table 186

Table 187

Table 188

Table 189

Table 190

Table 191

Table 192

Table 193

Table 194

Table 195

To

Elara, Maya, Ciaran, Caitlin and Cameron

to whom I owe much more than they will ever know

Fruit and Vegetables

Harvesting, Handling and

Storage

Third Edition

Volume 1

Introduction and Fruit

A.K. Thompson

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© 2015 by John Wiley & Sons, Ltd

This third edition first published 2015

Edition history: Iowa State Press (1e, 1996); Blackwell Publishing Ltd (2e, 2003)

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Library of Congress Cataloging-in-Publication Data

Thompson, A. K. (A. Keith)

Fruit and vegetables : harvesting, handling and storage / A.K. Thompson. – Third edition.

volumes cm

Includes bibliographical references and index.

Contents: Introduction and fruit

ISBN 978-1-118-65404-0 (cloth)

1. Fruit–Postharvest technology. 2. Vegetables–Postharvest technology. I. Title.

SB360.T45 2014

634′.0441 – dc23

2014013794

A catalogue record for this book is available from the British Library.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Cover image: © iStockphoto/raddanovic

About the Author

Anthony Keith Thompson is Professor of Horticulture at Hamelmalo Agricultural College in Keren, Eritrea. Previously he had been Professor of Postharvest Technology, Cranfield University, the United Kingdom; Team Leader, EU project at the Windward Islands Banana Development and Exporting Company; Principal Scientific Officer, Tropical Products Institute, London; Team Leader and Expert for the UN Food and Agriculture Organization in the Sudan and Korea; Advisor to the Colombian Government in postharvest technology of fruit and vegetables; Research Fellow in Crop Science, University of the West Indies, Trinidad; and Research Assistant, University of Leeds, the United Kingdom. Moreover, he is a consultant and advisor in many countries for many international, government and private organizations.

Preface

The awareness of the importance of plants in the human diet has developed into detailed scientific study. The role of plants in medicine seems to have always been known and even today searches are being constantly made to find chemicals in plants that can be used to prevent or cure disease in modern medicine. A vast range of plant species have been eaten throughout the history of mankind. Presumably, initially human beings started using plants and their products from gathering them in the wild and eventually finding ways of cultivating them. This is the history of the development of agriculture. Even now people are still collecting plants for food from the wild in tandem with the development of breeding new cultivars of these crops and improved ways of cultivating them. Keller and Tukuitonga (2007) stated that ‘Low fruit and vegetable intake was identified as an important risk factor for chronic diseases in the WHO World Health Report 2002. Overall, it is estimated that up to 2.7 million lives could potentially be saved each year if fruit and vegetable consumption was sufficiently increased.’ The nutritional properties of vegetables and fruit have been known for centuries. In the 18th century a French pharmacist Antoine-Augustin Parmentier demonstrated, for several years by his own diet, that all the nutrients required to sustain a healthy life were found in potatoes (Block 2008). The quality of the plant material in terms of nutrition and the maintenance of that quality and reducing their physical losses from harvest to reaching the consumer have been the subject of a vast number of research projects. Changes that can occur may be due to infections by microorganisms or by the physiological processes that continue in vegetables and fruit since they are still living organisms with life processes that are severed from their sources of renewal and sustenance.

The technology involved in getting fresh produce from the field to the consumer is enormously complicated because many of the crops are highly perishable and variable. This variability militates against simple solutions. The fresh produce trade would prefer not to be involved with this variation and complexity. They would prefer to be able to look up their particular crop on a chart, which will say it should be harvested, packaged and stored in a certain way. Information in this form is readily available but will rarely give the best results in terms of preserving the quality of the crop. The objective of this book is the same as the two previous editions, which is to provide a range of postharvest options from which the produce technologist can select. Additionally it puts into context our current state of knowledge on postharvest science and technology and thus identifies areas where research is needed.

In order to provide a context for understanding the differences in research results and interpreting them some background information has been supplied on each fruit or vegetable. Also some taxonomy is included because of the difficulties in knowing exactly which crop the researchers have referred to. This may well help in determining the differences in results. The information in this book and the way that it is presented is therefore largely what is perceived to be required by the industry. Also there is increasing pressure for universities to provide graduates who are more relevant to the needs of industry, and most students of postharvest science and technology will eventually work in the industry or in some way be associated with it; so the book will also serve their needs. The parts on tropical root crops have relied heavily on two of the publications of Daisy Kay. From 1970 Daisy and I worked together at the Tropical Products Institute in London. TPI subsequently became the Tropical Development and Research Institute. The 1973 edition of her Root Crops: Crop and Product Digest was so well received that it was decided in the Institute to produce a second edition. Because Daisy had died and because of research and overseas consultancy work no one suitably qualified in the Institute had sufficient time to revise Daisy's work and so Graham Gooding was employed and with the co-operation of members of the Institute produced the excellent second edition in 1987. C.W. Wardlaw and his associates working in Trinidad at what eventually became the University of the West Indies is also a major source of information. Wardlaw was the Head of the Botany Department at Manchester University in 1960 and 1961 when I worked there as a lowly gardener in their Botanic Gardens. I subsequently was responsible for sorting out Wardlaw's notes and data and those of his predecessor S.C. Harland in Trinidad when the library at the University was relocated in 1969 while I was working there as a Research Fellow. Another major source is the work of Dr J.M. Lutz and Dr R.E. Hardenburg published in the United States Department of Agriculture Bulletin 66, which I was pleased to see has been revised and is constantly updated on the Internet by some of the most experienced postharvest technologists.

The work of this book is based on a selective review of the literature and my experiences since I was first formally involved in postharvest technology in 1967. Since that time postharvest technology has taken me all over the world doing short consultancies and long-term assignments, of up to 3 years, meeting particular challenges in research, training and development of the fruit and vegetable industry. Although much of my time has been spent as an academic and government or United Nations adviser, I have always worked closely with the horticultural industry. The information in this book and the way that it is presented is therefore largely in a form that I perceive to be required by the industry.

In this third edition I have brought the information up-to-date and widened its scope by including some fruit and vegetables that were not included in the first two editions. Comments have been made on the lack of information and discussion on the benefits of consumption of fruit and vegetables and levels of various nutrients they may contain and how these may change postharvest. So some nutritional data has been included and I am indebted to the USDA nutrient database for much of this information. Also I have included more details on taxonomy since it has been pointed out that there is often confusion as to which crop is being referred to. I have also included a little on the origin and history of the crops for which I have relied to a considerable degree on the excellent publications of Julia Morton and J.W. Purseglove.

Acknowledgements

To Mr Allen Hilton, Dr Wei Yuqing, Dr Dick Sharples, Professor Don Tindall, Dr Sulafa Musa, Dr Bob Booth, Dr Andy Medlicott, Dr Robin Tillet, Dr James Ssemwanga, Mr David Bishop, Mr Devon Zagory, Mr Tim Bach, Silsoe Research Institute, FAO Rome, WIBDECO St. Lucia and Positive Ventilation Limited for use of photographs and other illustrative material. To Dr Graham Seymour and Dr John Stow for comments and help on the earlier editions. Selections from USDA nutrient data base, which is freely available, have been widely used and gratefully acknowledged.

Chapter 1

Preharvest factors on postharvest life

The quality of a crop at harvest can have a major effect on its postharvest life. There are numerous factors involved and these factors frequently interact giving complex interrelationships. In tree crops, fruit produced on the same tree and harvested at the same time may behave differently during marketing or when stored. The issues that influence produce quality include obvious things, such as harvest maturity and cultivar or variety, but also the climate and soil in which it was grown, chemicals which have been applied to the crop, and its water status. Many of these factors can also interact with time such as when fertilizers or irrigation is applied or the weather conditions near to the time of harvest.

An equation was proposed (David Johnson 1994, personal communication) to predict the probability of low temperature breakdown in apples in storage where variance accounted for 56%. This equation was based on preharvest factors such as temperature, rainfall and nutrient level in the leaves and fruit of the trees as follows:

equation

where:

c01-math-0002 = mean daily maximum temperature in June

c01-math-0003 = difference in mean daily maximum temperature in August and September

c01-math-0004 = total rainfall in August and September

c01-math-0005 = level of nitrogen in the leaves

c01-math-0006 = level of phosphorous in the fruit.

Nutrients

The soil type and its fertility affect the chemical composition of a crop. Excess or deficiency of certain elements from the crop can affect its quality and its postharvest life. Many storage disorders of apples are associated with an imbalance of chemicals within the fruit at harvest (Table 1).

Table 1 Storage disorders and other storage characteristics of Cox's Orange Pippin apples in relation to their mineral content (source: adapted from Rowe 1980)

The relation between the mineral composition of fruits and their quality and behaviour during storage is not always predictable (Table 2) but in some cases the mineral content of fruits can be used to predict storage quality. For good storage quality of Cox's Orange Pippin apples it was found that they required the following composition (on a dry matter basis): 50–70% N, 11% minimum P, 130–160% K, 5% Mg and 5% Ca for storage until December at 3.5 °C or 4.5% Ca with minimum storage in 2% O2 and <1% CO2 at 4 °C until March (Sharples 1980).

Table 2 Summary of the most consistent significant correlations between mineral composition (fruits and leaves) and storage attributes in a 3-year survey (1967, 1968 and 1969) of Cox's Orange Pippin commercial orchards (source: adapted from Sharples 1980)

The physiological disorder that results in the production of colourless fruit in strawberries is called albinism. The fruit, which were suffering from this physiological disorder, were also found to be softer. The ratio of potassium : calcium and nitrogen : calcium was found to be greater in fruit suffering from albinism than in red fruit (Lieten and Marcelle 1993). Albinism was associated with the cultivar Elsanta and some American cultivars, and the recommendation for control was either to grow only resistant cultivars or decrease the application of nitrogen and potassium fertilizers (Lieten and Marcelle 1993).

The application of fertilizers to crops has been shown to influence their postharvest respiration rate. This has been reported for a variety of fertilizers on several crops including potassium on tomatoes, nitrogen on oranges and organic fertilizers on mangoes. An example of this is that an imbalance of fertilizers can result in the physiological disorder of watermelon called blossom-end rot (Cirulli and Ciccarese 1981). However, care must be taken in interpreting experimental results since the application of fertilizers may simply be correcting nutrient deficiencies in the soil that may be having detrimental effects of the physiology of the crop.

Nitrogen

Generally crops that contain high levels of nitrogen typically have poorer keeping qualities than those with lower levels. Results on the effects of nitrogen fertilizer on the storage life have been variable. In shallots the highest incidence of sprouting was found in the treatment combination of 150 kg N ha−1, 50% top fall harvest and non-cured bulbs which accounted for 16.73% sprouting, while the least was observed from zero N, 75% top fall harvest and cured bulbs which was 2.37% at the end of 3 months of storage (Woldetsadik and Workneh 2010). Bhalekar et al. (1987) also observed that sprouting of onions was increased with increasing nitrogen levels from 0 to 150 kg N ha−1. Dankhar and Singh (1991) also reported that high dose of nitrogen produced thick-necked onion bulbs that increased sprouting in storage while Ystaas (1980) showed that the application of nitrogen fertilizer to pear trees did not affect the soluble solids content, firmness, ground colour or quality of the fruit. Kodithuwakku and Kirthisinghe (2009) applied different levels of urea fertilizer to growing cauliflowers and found no significant difference in the postharvest quality of cauliflower curds. However, they found that applying 50% of the recommended N fertilizer resulted in an extension in their postharvest life of 6 days longer than other treatments in storage in ambient conditions. Anonymous (2010) reported that limiting nitrogen fertilizer resulted in improved shape, size and storability of swedes (Brassica napus var. napobrassica).

Application of N fertilizer can affect postharvest quality. Link (1980) showed that high rates of N fertilizer to apple trees could adversely affect the flavour of the fruit. Comis (1989) reported that too much soil nitrogen could reduce the vitamin C content of Swiss chard. Rogozinska and Pinska (1991) found that loss of tuber weight during storage increased with increasing fertilizer rate but loss of starch was high only at high N rates (200 kg N ha−1). They also found a negative effect on the organoleptic value of tubers after 200 kg N ha−1, especially after 6 months of storage. Potatoes grown with high levels of N had lower amounts of free sugars at all times (Roe et al. 1990). High N levels delayed tuber formation resulting in more immature tubers when harvested at the same time compared with tubers grown with lower N levels (Bodin 1988). Admiraal (1988) found that tuber density was less within those that had been grown in 150 kg N ha−1 applied 4 weeks after harvest and after 3 months of storage at 10 °C compared with those grown without N fertilizer. Kolbe et al. (1995) found that at harvest, the glucose and fructose contents in tubers were lower for those that had been grown with high rates of N fertilizer compared to low rates or absence of fertilizers, but throughout storage, reducing sugar accumulation increased, sucrose reduction decreased and ascorbic acid content increased. N decreased reducing and non-reducing sugar content after storage for 3 months at 10 or 15.5 °C (Badshah et al. 1990). During storage of potatoes at 4 °C and 90% r.h. there was an increase in water loss of 54% as a result of N fertilization (Kolbe et al. 1995). Woldetsadik and Workneh (2010) found that with a basic dressing of 92 kg ha−1 P2O5 increasing N levels (0, 50, 75 or 100 kg ha−1) showed proportional increase in the shallot bulb pungency levels, but the dry matter, TSS, total sugars and reducing sugars were not significantly affected either at harvest or during storage. However, there were increments in the percentage bulb rotting, sprouting and weight loss with increased N levels. Since nitrogen fertilizer can affect quality it may be summarized that they could affect their susceptibility to handling damage. However, increasing levels of N fertilizer application did not affect the susceptibility of potato tubers to mechanical damage (Divis and Sterba 1997) although Kolbe et al. (1995) found that high N resulted in an increase in pectic substances and lower cellulose content.

Application of nitrogen fertilizer to pome fruits and stone fruits has been shown to increase their susceptibility to physiological disorders and decrease fruit colour (Shear and Faust 1980). High nitrogen increased the susceptibility of Braeburn apples to flesh and core browning during storage (Rabus and Streif 2000). In fertilizer trials on avocados Köhne (1992) showed that the application of nitrogen could reduce the percentage of clean fruit, but where it was combined with magnesium and potassium there was no effect. In a field experiment in the Netherlands there were variable results to field application of nitrogen fertilizer, but during storage at 12 °C and 90% r.h. for 10 days after the first harvest, nitrogen had no effect on the yellowing of small Brussels sprouts. However, the application of 31 kg N ha−1 as calcium nitrate resulted in increased yellowing of large sprouts. At the second harvest, no effect of nitrogen was observed (Everaarts 2000). Nitrogen fertilizer has also been shown to affect susceptibility to disease. Bunches of Italia grapes from vines treated with 35% nitrogen as urea and 65% as Ca(NO3)2 through fertigation had less water loss and less decay after 56 days of storage at 2–4 °C and 90–95% r.h. than the bunches from treatments that had higher levels of nitrogen (Choudhury et al. 1999). Alternaria alternata, Cladosporium herbarum, Penicillium sp., Rhizopus spp. and Aspergillus niger caused storage decay in those trials. Conversely, Pertot and Perin (1999) showed that excessive nitrogen fertilization significantly increased the incidence of rot in kiwifruit during subsequent cold storage, both in the year of application and in the following year. Woldetsadik and Workneh (2010) found that there was increased rotting of shallots, sprouting and weight loss with increased N levels. Translucence in pineapple has been related to high nitrogen as well as high radiation, temperatures and rainfall during growth (Paull and Reyes 1996). Srikul and Turner (1995) reported that high N applications reduced green life of banana fruit.

Phosphorus

In the limited published work, ensuring sufficient phosphorous in the crop generally had beneficial postharvest effects. For example in cucumber fruits phosphorus nutrition can alter their postharvest physiology by affecting membrane lipid chemistry, membrane integrity and respiratory metabolism. Cucumbers were grown in a greenhouse under low and high phosphorus fertilizer regimes by Knowles et al. (2001). Tissue phosphorus concentration of the low phosphorus fruits was 45% of that of fruits from high phosphorus plants. The respiration rate of low phosphorus fruits was 21% higher than that of high phosphorus fruits during 16 days of storage at 23 °C, and the low phosphorus fruits began the climacteric rise about 40 h after harvest, reached a maximum at 72 h and declined to pre-climacteric levels by 90 h. The difference in respiration rate between low and high phosphorus fruits was as high as 57% during the climacteric. The respiratory climacteric was different to the low phosphorus fruits and was not associated with an increase in fruit ethylene concentration or ripening. Kolbe et al. (1995) found that increasing the levels of phosphate fertilizer during the growth of potatoes resulted in decreased weight losses during storage at 4 °C and 90% r.h. for 6 months. Phosphorus levels in tubers were reported to be 0.093% by Banks and Greenwood (1959). Singh et al. (1998) found that the application of 100 kg ha−1 of phosphorus minimized the weight loss, sprouting and rotting in onions during 160 days of storage compared to lesser applications.

Potassium

Generally application of potassium fertilizers had beneficial postharvest effects, but there was some evidence of increases in crop acidity, and application of high rates could have negative effects. Cirulli and Ciccarese (1981) found that the application of potassium fertilizer to watermelons was shown to decrease the respiration rate of the fruit after harvest. In tomato fruits dry matter and soluble solids content increased as potassium rate increased, but there were no significant differences in TA at different potassium rates (Chiesa et al. 1998). Spraying Shamouti orange trees with a potassium fertilizer increased potassium concentration in the fruit and reduced the incidence of the physiological fruit storage disorder called superficial rind pitting (Tamim et al. 2000). Hofman and Smith (1993) found that the application of potassium to citrus trees could affect the shape of their fruits and increase their acidity, although this effect was not observed when potassium was applied to banana plants. High potassium generally increased acidity in strawberries, but this effect varied between cultivars (Lacroix and Carmentran 2001). A soil drench with potassium chlorate extend the fruiting season of longan (Subhadrabandhu and Yapwattanaphun 2001, Jiang et al. 2002). Rogozinska and Pinska (1991) found that 320 kg K2O ha−1 had a negative effect on the organoleptic value of potato tubers, especially after 6 months of storage.

There is compelling evidence of a significant reduction in susceptibility of potato tubers to damage with increasing the rate of application of potassium fertilizer. However, the effect is not large and was primarily observed for the potassium deficient range of concentrations (McGarry et al. 1996). In a field experiment by Singh et al. (1996) tubers were given 0–180 kg K2O ha−1 and when tubers were stored for 14 weeks losses and sprouting were the lowest where 180 kg K2O had been applied. In contrast Sharma and Ezekiel (1993) found that sprout weight was increased with K2O application after 60 days of storage but tuber weight loss and sprouting were not affected. They also found that dry matter, ascorbic acid and total sugar content of tubers increased with application of K2O. Panique et al. (1997) reported a reduction in specific gravity with increasing applied potassium in most of the site-years, and a significant decrease in hollow heart with increasing rate of potassium fertilizer application was observed in 4 of 11 site-years. They also reported that the incidence of Rhizoctonia solani was generally not affected by potassium rate, but there was a tendency in some site-years for a higher disease incidence when KCl was used instead of K2SO4 (Panique et al. 1997). Kolbe et al. (1995) found that at harvest, the glucose and fructose contents in tubers were reduced by high potassium fertilizer rates compared to low or absence of fertilizers, but throughout storage, reducing sugar accumulation increased, sucrose reduction decreased and ascorbic acid content increased. Badshah et al. (1990) found that potassium fertilizer had a negative effect on tuber quality only at rates above 240 kg ha−1.

Calcium

The physiological disorder of stored apples called bitter pit (Figure 1) is principally associated with calcium deficiency during the period of fruit growth and may be detectable at harvest or sometimes only after protracted periods of storage (Atkinson et al. 1980). The incidence and severity of bitter pit are influenced also by the dynamic balance of minerals in different parts of the fruit as well as the storage temperature and levels of O2 and CO2 in the store atmosphere (Sharples and Johnson 1987). de Freitas et al. (2010) observed in Granny Smith that calcium accumulation into storage organelles and calcium binding to the cell wall represent important contributors to bitter pit development in apples. They found an increase in the expression of genes encoding four pectin methylesterases, a greater degree of pectin de-esterification and therefore more calcium binding sites in the cell wall. They also reported a higher fraction of the total cortical tissue calcium content that was bound to the cell wall in pitted fruit compared with non-pitted fruit. Cells of the outer cortical tissue of pitted fruit consistently had higher membrane permeability than outer cortical cells of non-pitted fruit. Low calcium levels in fruit were also shown to increase the susceptibility of Braeburn apples to flesh and core browning (Rabus and Streif 2000). Calcium has also been associated with postharvest factors in other fruit for example in tomatoes blossom-end rot has been associated with low calcium and high potassium fertilizers (Ho et al. 1993). In papayas, low mesocarp calcium concentrations have been linked with fruit softening (Qiu et al. 1995). In a 3-year study of potatoes by Clough (1994) on fine sandy loam soil calcium sulphate was applied before planting and calcium nitrate as a side dressing. After 4 months of storage at 7 °C, severity and percentage of tubers with internal brown spot were reduced by calcium application either before planting or as a side dressing.

Figure 1 Bitter pit on a Red Delicious apple in Turkey.

The treatment of tomato plants with a foliar spray of calcium or a postharvest dip effectively increased cell wall calcium, which is associated with fruit texture (Wills and Tirmazi 1979). Niitaka pears from trees that had been supplied with liquid calcium fertilizer were firmer after storage than fruit from trees that had not been treated (Moon et al. 2000). Blueberry plants that had calcium sulphate applied to them at 0.06 kg m−2 had 10% more calcium content within the cell wall at harvest the following year and less softening and weight loss during storage at 2 °C for 23 days compared to those that had not had the treatment (Angeletti et al. 2010). Kiwifruit vines of the cultivar Hayward were sprayed with liquid calcium (Nutrical) at 9.33 L ha−1 on 3 days between fruit set and 10 days before harvest. During controlled atmosphere storage kiwifruits from vines that had been sprayed with 9.33 L ha−1 of Nutrical were firmer and of better quality than fruits that had not been sprayed (Basiouny and Basiouny 2000). Ortiz et al. (2012) found that spraying Fuji Kiku-8 apple trees with calcium improved the preservation of the middle lamella in fruit cells by higher contents of ionically bound pectins leading to higher fruit firmness levels at commercial harvest. Matrix glycan breakdown was also delayed in response to calcium treatment. Calcium applications partially suppressed pectinmethylesterase, pectate lyase, β-galactosidase, α-l-arabinofuranosidase and β-xylosidase activities, without any apparent relationship with ethylene production rate.

Besada et al. (2008) reported that calcium nitrate applied to fruit of the persimmon cultivar Rojo Brillante prior to harvesting combined with 1-MCP applied postharvest delayed the symptoms of chilling injury and extended their storage at 1 °C for almost 3 months. Lower chilling injury occurred in kiwifruit during storage at 0 °C for up to 42 weeks from vines that had been sprayed with 1% calcium chloride four times during fruit development. Low temperature breakdown incidence was assessed after 5 days at 20 °C subsequent to storage (Gerasopoulos and Drogoudi 2005). Hartman et al. (2000) found that calcium chloride in the irrigation water resulted in mushrooms that were more resistant to the negative effects of excessive handling or bruising.

Fruit weight loss was reduced following liquid calcium fertilizer treatment, but there was no effect on soluble solids contents (Moon et al. 2000). Calcium sulphate applied to sapodilla trees at up to 4 kg per tree once every week for the 6 weeks prior to harvest improved the appearance of fruit, pulp colour, taste, firmness, aroma and texture after storage in ambient conditions (Lakshmana and Reddy 1995). High calcium fertilizer levels reduced acidity of strawberries, but contributed to the loss of visual fruit quality after harvest (Lacroix and Carmentran 2001). Spraying guava trees with 1% calcium nitrate resulted in the lowest mean loss in weight, respiration rate and acidity, highest TSS and ascorbic acid and maintained the firmness of fruits during storage longer than the fruit that had not been sprayed or those sprayed with other calcium nitrate concentrations. Spraying clusters of both longkong and langsat fruit with 5% calcium chloride 10 and 11 weeks after fruit set reduced fruit drop and increased fruit firmness, TSS content and the ratio of TSS to TA (Rattanapong et al. 1995). Potato tuber quality during storage for 6 months at 25 °C was greatly increased in tubers that had been grown in nutrient solution containing 972 mg Ca L−1 compared to those with zero or lower calcium concentrations in the solution (Paiva et al. 1997). Addition of calcium chloride to irrigation water increased calcium content and improved quality of mushrooms independent of inherent calcium content (Varoquaux et al. 1999). Hartman et al. (2000) also showed that significant improvements in mushroom quality resulted from addition of 0.3% calcium chloride to the irrigation water but the treatment slightly reduced crop yield. The effect of the calcium chloride was to improve initial whiteness at harvest and reduce postharvest browning compared to those not treated. When calcium chloride and sodium selenite were both added, the positive effects remained and all these negative trends were reversed.

Guava trees that had been sprayed with 1% calcium nitrate had reduced incidence of postharvest disease caused by Pestalotia psidii after 9 days of storage compared to fruit that had not been sprayed (Singh and Singh 1999). Chervin et al. (2009) reported that spraying vines with a 16% ethanol solution containing 1% calcium chloride reduced grey mould in the grape cultivar Chasselas from 15% in controls to 5% development during 6 weeks of cold storage. This was on fruit picked at a late harvest date and the treatment did not result in significant changes in fruit quality assessed by sensory analysis of healthy berries. In a 3-year study of the apple cultivar Idared Holb et al. (2012) found that integration of preharvest calcium sprays and CA storage minimized fruit injury/infection particularly brown rot incidence caused by Monilinia fructigena during long-term storage.

Magnesium

In potatoes the influence of magnesium and calcium in the cell wall and middle lamella on resistance to postharvest diseases was studied in two genotypes with large differences in their levels of resistance. Increased content of magnesium, especially in the periderm and cortex, clearly improved resistance to Phoma exigua var. foveata but not to Fusarium solani var. coeruleum. The effect of magnesium was greater than that of calcium and the results indicated that the ratio of Mg : Ca might be of importance for resistance to gangrene. The pectin-bound Mg that gives a firmer cell wall and middle lamella than the pectin-bound calcium can explain this effect (Olsson 1988).

Micronutrients

In India Shashirekha and Narasimham (1990) found that dipping potato seed tubers in aqueous solutions of trace element salts decreased both sprouting and microbial spoilage during storage in ambient conditions.

Soil acidity

Soil acidity can affect not only the yield but also the quality of a crop, which in turn could affect postharvest attributes. However, the literature does not provide confirmation of this assumption. For example Kihurani et al. (2008) showed that growing sweet potato in soil at the different pH levels of 4.6, 5.8 and 6.1 did not significantly influence postharvest pathological deterioration of the roots caused by Rhizopus oryzae and Botryodiplodia theobromae.

Organic production

The market for organically produced food is increasing. There is conflicting information on the effects of organic production of fruit and vegetables on their postharvest characteristics. Organic production has been shown to result in crops having higher levels of postharvest diseases. Massignan et al. (1999) grew Italia grapes both conventionally and organically and after storage at 0 °C and 90–95% r.h. for 30 days they found that organic grapes were more prone to storage decay than those grown conventionally. In another case there was evidence that organic production reduced disease level. In samples from organically cultivated Bintje and Ukama potato tubers the gangrene disease (Phoma foveata) levels were lower compared with conventionally cultivated ones. However, there was no such difference in King Edward and Ulama tested 4 months later. The dry rot (Fusarium solani var. coeruleum) levels were generally lower in organically cultivated potatoes compared with tubers from the conventional system (Povolny 1995).

Producing crops organically can have other effects. Although harvested on the same day, conventionally produced kiwifruits were generally more mature, as indicated by TSS concentrations, but their average firmness did not differ significantly for those produced organically. Despite the differences in maturity, whole fruit softening during storage at 0 °C did not differ significantly with production system. However, organically grown fruits nearly always developed less soft patches on the fruit surface than conventionally grown fruits (Benge et al. 2000). The effect of organic compost fertilization on the storage of Baba lettuce was evaluated by Santos et al. (2001). The organic compost was applied at 0, 22.8, 45.6, 68.4 and 91.2 tonnes per hectare on a dry matter basis, with and without mineral fertilizer. They reported that during storage at 4 °C lettuce grown in increasing rates of organic compost had reduced levels of fresh weight loss by up to 7%. The chlorophyll content decreased during storage when plants were grown with 45.6 and 91.2 tonnes per hectare of organic compost with mineral fertilizers compared to the other levels. The fertilization with organic compost and mineral fertilizer altogether resulted in plants with early senescence during cold storage.

In a survey in Japan about the fruit quality of Philippine bananas from non-chemical production, the problems highlighted all related to management practices and none to the effects of organic production on postharvest aspects (Alvindia et al. 2000). However, in Britain Nyanjage et al. (2000) found that imported organically grown Robusta bananas ripened faster at 22–25 °C than non-organically grown bananas as measured by peel colour change, but ripe fruit had similar TSS levels from both production systems. The peel of non-organic fruits had higher nitrogen and lower phosphorus contents than organic fruits. Differences in mineral content between the pulp of organic and non-organic fruits were much lower than those between the pulp and the peel.

Light

Fruits on the parts of trees that are constantly exposed to the sun may be of different quality and have different postharvest characteristics than those on the shady side of the tree or those shaded by leaves. Citrus and mango fruits produced in full sun generally had a thinner skin, a lower average weight, lower juice content, a lower level of acidity but a higher total and soluble solids content (Sites and Reitz 1949, 1950a, 1950b).

Woolf et al. (2000) showed that during ripening of avocados at 20 °C, fruit that had been exposed to the sun showed a delay of 2–5 days in their ethylene peak compared with fruits that had been grown in the shade. The side of the fruit that had been exposed to the sun was generally firmer than the non-exposed sides, and the average firmness of exposed fruits was higher than that of shaded fruits. After inoculation with Colletotrichum gloeosporioides the appearance of lesions on exposed fruits occurred 2–3 days after shaded fruits. There is also some evidence that citrus fruits grown in the shade may be less susceptible to chilling injury when subsequently kept in cold storage. Specific disorders such as water core in apples and chilling injury in avocado can also be related to fruit exposure to sunlight (Ferguson et al. 1999).

Sunscald can occur on fruits that are exposed to the sun; for example, in bananas it can result in damage to the peel that causes discoloration as they ripen (Figure 2). In tomatoes and peppers sunscald is most prevalent on the green fruit, where white or yellow blisters will develop on the sides of the fruit that are exposed to the sun. Continued exposure may result in the damaged areas becoming papery, flattened and greyish with mould growth and eventual rotting. Schrader (2011) described sunburn necrosis on apples where excess solar radiation is converted to heat energy and causes a high fruit surface temperature of about 52 °C resulting in thermal death of cells. He also described a second type called sunburn browning that is caused by the combination of temperatures of 46–49 °C and high solar radiation. Cell death is not induced, but several pigment changes occur and the apple peel typically turns yellow or brown.

Figure 2 Banana sunscald.

Amarante et al. (2002) reported that bagging of pears reduced sunscald. Silimela and Korsten (2000) tested plastic caps with an added inner wool lining to protect mango fruit against sunburn. They found that the capped fruit had significantly less sunburn damage than non-capped fruit. However, Muchui et al. (2010a, 2010b) found that in bananas perforated shiny blue bunch covers resulted in a few fingers of top hands of some bunches suffered sunburn. Previously Weerasinghe and Ruwanpathirana (2002) reported that bagging of bananas resulted in sun scorching of the fruits irrespective of the colour of the bunch covers. Pulling leaves over the covered bunches during growth may reduce or prevent sunburn, or inserting a newspaper on the inside of the bunch covers to cover top hands has also been shown to work (Muchui et al. 2010a, 2010b). Schrader (2011) reported that a combined sprayable formulation of carnauba wax and organo-clay emulsion was more effective in protecting apples from sunburn browning. Iglesias and Alegre (2006) tested crystal (transparent) and black nets on the protection of apples and found that both nets reduced fruit temperature and the incidence of sunburn improving their skin quality and protecting the fruit from hail damage. They noted some minor effects on fruit quality and their annual cost was €1874 ha−1 for crystal nets and €1612 ha−1 for black nets.

Day length

Day length is related to the number of hours of light in each 24-h cycle, which varies little near the equator but varies between summer and winter in increasing amounts further from equator. Certain crop species and varieties have evolved or been bred for certain day lengths. If this requirement is not met using an unsuitable variety then the crop may still be immature at harvest. An example of this is the onion where cultivars, which have been bred to grow in temperate countries, where the day length is long and progressively getting shorter during the maturation phase, will not mature correctly when grown in the tropics where day length is shorter and less variable during the maturation period. In such cases the onion bulbs had very poor storage characteristics (Thompson 1985). Aborisade and Ayibiowu (2010) studied the effects of day length postharvest on ripened the tomato cultivars Roma and Beske. They were harvested at the mature-green, breaker, turning or pink stages and then stored at 28 °C either in 12 h naturally alternating light and dark or in complete darkness. Ripening progressed in complete darkness more quickly than in 12 h naturally alternating light and dark in breaker fruit. However, the difference was more pronounced in Roma than in Beske. Fruit initially at the turning stage did not show any significant effect of photoperiod in Roma but did by day 6 in Beske. Generally photoperiod had more significant effect at the mature-green and breaker stages than at the turning and pink stages of ripening.

Temperature

The temperature in which a crop is grown can affect its quality and postharvest life. An example of this is pineapple grown in Australia. Where the night-time temperature fell below 21 °C internal browning of the fruit could be detected postharvest (Smith and Glennie 1987). The recommended storage temperature for Valencia oranges grown in California is 3–9 °C with a storage life of up to 8 weeks. The same cultivar grown in Florida can be successfully stored at 0 °C for up to 12 weeks. Oranges grown in the tropics tend to have a higher sugar and total solids content than those grown in the subtropics. However, tropical grown oranges tend to be less orange in colour and peel less easily. The latter two factors seem to be related more to the lower diurnal temperature variation that occurs in the tropics rather than the actual temperature difference between the tropics and subtropics.

The apple cultivar Cox's Orange Pippin grown in the United Kingdom can suffer from chilling injury when stored below 3 °C, while those grown in New Zealand can be successfully stored at 0 °C. However, this may be a clonal effect since there are considerable differences in many quality factors, including taste and colour, between clones of Cox's Orange Pippin grown in the United Kingdom and those grown in New Zealand (John Love 1994, personal communication). In Braeburn apples growing conditions were shown to influence scald, browning disorder and internal cavities during storage. So following a cool growing season it was recommended that they should be stored in air at 0 °C to avoid the risks of those disorders, but they may be stored in controlled atmospheres after warm seasons because this retains texture and acidity better (Lau 1998). Ferguson et al. (1999) found that in both apples and avocados, exposure of fruits to high temperatures on the tree could influence the response of those fruits to low and high postharvest temperatures. Specific disorders such as water core in apples and chilling injury in avocado can also be related to fruit exposure to high temperatures, disorders such as scald in apples may be related to frequency of low temperature exposure over the season. Oosthuyse (1998) found that cool, humid or wet conditions on the date of harvest strongly favour the postharvest development of lenticel damage in mangoes. Conversely, dry, hot conditions discouraged the postharvest development of lenticel damage. Woolf et al. (1999) found that Hass avocados exposed to direct sunlight in ambient temperatures of 15–25 °C had a flesh tissue reaching 43 °C. Fruit exposed to the sun had less external damage from hot water treatments of 50 °C for up to 10 min and less external chilling injury when stored at 0.5 °C for up to 28 days. Leakage of electrolytes from skin tissue from fruit exposed to the sun did not increase during storage, while that from shaded fruit increased by about 60%. Also fruit exposed to the sun took longer to ripen than shaded fruit. Mercado-Silva et al. (1998) found that guava fruit growth showed a double sigmoid pattern, with spring/summer fruit needing 130 days, while autumn/winter fruit required 190 days to reach the ripe stage. Autumn/winter fruit had higher TSS, TA and ascorbic acid concentrations than spring/summer fruit. The climacteric peaks in respiration rate and ethylene production were reached after 7–8 days in autumn–winter fruit as compared with 4–5 days in spring/summer fruit.

Water relations

High rainfall or heavy irrigation can affect fruit growth which in turn can also increase skin cracking in fruit including cherries, apples and tomatoes. Generally crops that have higher moisture content have poorer storage characteristics. For example hybrid onion cultivars that tend to give high yield of bulbs with low dry matter content but only a short storage life (Thompson et al. 1972a, 1972b, Thompson 1985). Srikul and Turner (1995) reported that low irrigation reduced green life of bananas, but if bananas are allowed to mature fully before harvest and harvesting is shortly after rainfall or irrigation the fruit can easily split during handling operations, allowing microbial infection and postharvest rotting (Thompson and Burden 1995). If oranges are too turgid at harvest the oil glands in the skin can be ruptured releasing phenolic compounds and causing oleocellosis (Wardlaw 1937). Some growers harvest crops in late morning or early afternoon. In the case of leaf vegetables such as lettuce they may be too turgid in the early morning and the leaves are soft and more susceptible to bruising (John Love, personal communication). Also too much rain or irrigation can result in the leaves becoming brittle with the same effect. Irrigating crops can have other effects on their postharvest life. In carrots heavy irrigation during the first 90 days after drilling resulted in up to 20% growth splitting, while minimal irrigation for the first 120 days followed by heavy irrigation resulted in virtually split-free carrots with a better skin colour and finish and only a small reduction in yield (McGarry 1993). Shibairo et al. (1998) grew carrots with different irrigation levels and found that preharvest water stress lowered membrane integrity of carrot roots, which may enhance moisture loss during storage. The effects of water stress, applied for 45 or 30 days before flowering on Haden mangoes, which were stored at 13 °C for 21 days after harvest, were studied by Vega Pina et al. (2000). They found that the 45-day fruits exhibited a higher incidence and severity of internal darkening, were firmer, contained a higher content of TA and had redder skins than 30-day fruits.

In a study of the storage of onions grown in Tajikistan by Pirov (2001) under various irrigation regimes it was found that if onions are to be used fairly quickly, then maximum yields can be achieved by keeping the soil at 80–90% of field capacity. However, when they were stored for 7 months at 0–1 °C and 75–80% r.h. the best irrigation regime was 70% of field capacity throughout the growing season.

Broccoli, cultivated under low (0.40 MPa) and normal (0.04 MPa, equivalent to field capacity) soil water content, were stored at either 1 °C or room temperature of 23 °C. Low soil water content and storage at 1 °C gave the best preservation of colour, antioxidant activity, l-ascorbic acid and 5-methyl-tetrahydrofolate contents. The phenolic compounds were reduced over time, independent of cultivation and storage conditions (Cogo et al. 2012).

Splitting during growth can affect postharvest losses. The incidence of damage in carrots was shown to be affected by the total amount of irrigation and the time when it was applied. Heavy irrigation during the first 90 days after sowing resulted in up to 20% growth splitting, while minimal irrigation for the first 120 days followed by heavy irrigation resulted in virtually no splitting with a better skin colour and finish and only a small reduction in yield (McGarry 1993). Carrots contain an antifreeze protein that improves storage performance. Carrots grown in temperatures of less than 6 °C accumulated higher levels of this protein and subsequently showed less electrolyte leakage from cells, slightly higher dry matter and less fungal infestation than carrots grown in warmer temperatures. However, levels also vary between environments in which the carrots had been grown (Galindo et al. 2004, Kidmose et al. 2004).

Rachis browning can occur postharvest and Balic et al. (2012) studied the effects of various postharvest treatments and found a genetic relationship with this disorder. They suggested a putative cellular regulatory mechanism of water loss and senescence in rachis that most likely involved ethylene and oxidative stress metabolism. They found that cytokinin applied to the fruit 1 day before harvest lowered percentage rachis browning after 90 days at 0 °C plus 2 days at 20 °C compared to those not treated.

Luna et al. (2012) studied the effects of five drip irrigation systems (excess 50%, excess 25%, control, deficit 25% and deficit 50%) on the postharvest quality fresh cut iceberg lettuce. They found that visual quality was lower on those from the highest irrigation regime and they had increased off-odours. Also the midrib tissue had a more than 17-fold increase in phenylalanine ammonia lyase activity from the highly irrigated lettuce. They concluded that the quality and shelf life of the fresh cut lettuce were better preserved by reduced irrigation.

Production system

Clearly the system in which a fruit or vegetable is grown including grafting onto rootstocks and pruning can affect its quality and postharvest characteristics. Lower chilling injury occurred in kiwifruit during storage at 0 °C for up to 42 weeks from vines that had been pruned in summer compared to those that had not. There was also less chilling injury in fruit from short shoots compared with those harvested from medium and long shoots. Chilling injury incidence was assessed after 5 days at 20 °C subsequent to storage (Gerasopoulos and Drogoudi 2005). Not much information could be found on the effects of tree age on the postharvest characteristics of fruit, but fruit from young Braeburn apple trees were more susceptible to flesh and core browning than those from older trees (Rabus and Streif 2000). In the tropics flowering time of fruit trees can affect postharvest life of fruits. Mayne et al. (1993) have shown that jelly-seed, a physiological disorder of mangoes, was associated with flowering time in Tommy Atkins. They showed that delaying flowering by removing all the inflorescences from the tree greatly reduced jelly-seed in fruit that developed from the subsequent flowering. These fruit were larger than those produced from trees where the inflorescences had not been removed but the number of fruit per tree was reduced.

For various reasons fruit trees are grafted onto rootstocks and the rootstocks can have a profound effect on the performance of the crop, including its postharvest life. Considerable work was done, particularly at Horticultural Research International at East Malling in the United Kingdom and its predecessors, on the use of different rootstocks to control tree vigour and cropping. Tomala et al. (1999) found that the rootstocks had a considerable effect on maturation and storage of Jonagold apples. Fruits from trees on the rootstock B146 had the lowest respiration rates and ethylene production after storage for 2 and 4 months at 0 °C but not after 6 months. Fruits from trees on P60 and 62-396 started their climacteric rise in respiration rate 5–7 days earlier than fruits from PB-4. Fruits were more yellow at harvest from trees on P60, 62-396 and M.26; fruit colour was weak on PB-4 and fruits from these trees coloured most slowly during storage. Rootstocks also affect other fruit crops. In some work in South Africa on avocados (Smith and Köhne 1992) it was shown that the cultivar Fuerte grown on seedling rootstocks showed a large variation in both yield and quality of fruit. There was also some indication that rootstocks, which gave a low yield generally, produced a higher proportion of low quality fruit. Köhne (1992) also showed similar results for the avocado cultivar Hass on different clonal rootstocks (Table 3). Rootstock studies conducted in Australia on Hass avocado by Willingham et al. (2001) found that the rootstocks had a significant impact on postharvest anthracnose disease susceptibility. Differences in anthracnose susceptibility were related to significant differences in concentrations of antifungal dienes in leaves, and mineral nutrients in leaves and fruits, of trees grafted to different rootstocks.

Table 3 Effect of clonal rootstocks on the yield and quality of Hass avocados (source: adapted from Smith and Köhne 1992)

Fruits of Ruby Red