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MCROFICHE REFERENCE LIBRARY A project of Volunteers in Asia Vegetable Seeds for the Tropics, Bulletiil 301 - by G.J.H. Grubben Published by: Swiss Center for Appropriate Technology (SKAT) Varnbuelstrasse 14 CH-9000 St. Gall SWITZERLAND Available from: same as above Reproduced by permission. Reproduction of this microfiche document in any form is subject to the same restrictions as those of the original document. Vegetable Seeds for the Tropics G. J. H. Grubben Bulletin 301 Department of Agricultural Research Koninklijk lnstituut voor de Tropen Amsterdam, 1978 Copyright under the Berne Convention. All rights are reserved. Apart from any fair dealing for the purpose of private study, research, criticism or review, as penritted under the Copyright Act, 1956, no part of this publication may be repro&iced, stored in a retrieval system, or transmitted, in any form or by any means, ele :tron- ic, electrical, chemical, mechanical, photocopying, recording or otherwise, wi,hout the prior permission of the copyright owner. Enquiries should be addressed to the Royal Tropical Institute, Amsterdam @ 1978 Koninklijk Instituut voor de Tropen, Amsterdam TABLE OF CONTENTS 1. Vegetable growing and seed supply in the tropics I 7 1.1 Introduction j 7 1.2 Economic and nutritional value of vegetables / 7 1.3 Seed supply in various growing systems / 8 1.4 Problems of vegetable seed production in the tropics / 9 2. Climatic influences / 10 2.1 Climate and vegetable growing / 10 2.2 Climate and seed production 1 12 2.3 Climate and seed storage / 13 3. Seed production for home use / 19 3.1 Selecting and harvesting / 19 3.2 Separation / 19 3.3 Drying 1 20 3.4 Storage 1 20 4. Small scale co,nmerciaI seed production j 22 4.1 Agronomy j 22 Variety testing / 22 Production of breeder seed and foundation seed j 22 Production of market seed j 23 4.2 Technology / 23 Cleaning / 23 Drying / 24 Disinfection j 25 Storage j 25 Packaging / 26 Testing / 26 4.3 Distriiution / 28 5. Seed importation / 29 5.1 Principles / 29 5.2 Varieties recommended ior the tropics j 30 5.3 List of seed companies for import / 33 6. Literature I 35 7. Names of vegetables commonly cultivated in the tropics j 38 . ACKNOWLEDGEMENTS Thanks are due to Dr. N.G. Hogenboom of the Institute for Horticultural Plant Breeding in Wageningen and to Mr. J. ter Veen for their comments and to Miss V.M. Russell for the correction of the text. 1. VEGETABLE GROWING AND SEED qUPPLY IN THE TROPICS I.. 1 Introdu.ction In temperate areas vegetable growing has become an extremely technical activity. The grower can make his choice from a great diversity of cultivars’ (varieties) which are offered by numerous seed companies. All these cultivars have been bred for prevailing climatic conditions and cultivation methods and for the quality of produce as required by the customer. The price is usually high, but the commercial grower and the common home gardener are willing to purchase these guaranteed and high quality seeds, since seed costs are only a very small part of the total production costs. Good seed pay:! In the tropics, commercial veget able growing is increasing rapidly in order to meet the demands of the urban centres. Part of the vegetable seeds are purchased from the same large seed companies which supply growers in temnerate countries. But the fact remains that these cultivars have been bred for a climate, for cultivation methods and for customers’ requirements of quality and taste which are not at all the same as in tropical countries. On the other hand, a great deal of the seeds used by commercial growers and almost all the seeds used by the home gardener in the tropics are locally produced. This is especially true for the typical tropical species. Unfortunately, these locally produced seeds are often very heterogeneous (mixtures of different types) and their germination is poor. This bulletin is meant to give guideli?es for local seed growers, for extension workers and for vegetable growers, both commercial and non-commercial, to obtain high quality seeds. Bad seed gives an irregular stand, weak seedlings, a low yield and an inferior product. Good seed means a good start for a high yield of good quality vegetables. 1.2 Economic and nutritional value of vegetables In this bulletin the term ‘vegetables’ will be used for plants which produce an zlueous foodstuff, rich in water, poor in calories and mostly consumed as an addition to the starchy basic food rich in calories. Starchy tubers such as sweet potato, Irish potato, cassava, yam and cocoyam, and also grain legumes (pulses) such as common dry bean, cowpea, chick pea and horse bean fall outside our definition of vegetables. Only real vegetables propagated by dry seed are treated here, excluding the fresh one-seeded chayote fruit and vegetatively propagated types like garlic, bamboo and Sauropus, In developing countries - which are located mostly in the tropics - the average daily per capita vegetable consumption is about 100 g against 220 g in developed countries. At least three quarters of the vegeLdbles consumed in temperate, developed countries are produced by highly technical, commercial enterprises, whereas in the tropics less than half of the consumed quantity is commercialized. These statements are broad generalizations and great local variations can be observed. 1. ‘Cultivar’ is a con;iRoniy used international word which means ‘race’ or ‘cultivated variety’. a distinct group of plants of a certain cultivated species; abbreviated as cu., plural cm. 7 Vegetables are important as protective foods, providing vitamins and minerals. The most deficient vitamin in the tropics is vitamin A. This vitamin is largely present in all darkgreen leaf vegetables and also in some other species such as carrot, pumpkin and broccoli, in the form of carotene. Vitamin C, iron and calcium are also very important. The best sources of these nutrients are the cheapest ones, the green leaf vegetables. An average daily consumption of 150 g of vegetables per capita can be taken as a target, provided that one third of this quantity consists of vegetables. 1.3 Seed supply in various growing systems The following systems for vegetable growing in the tropics may be distinguished: a. collection of wild plants from the spontaneous vegetation. At present about 1500 vegetable species, mainly in the humid tropical lowlands and shifting cultivation areas are consumed. Some hundreds of species grow in the fields and are considered as weeds, although they are protected and consumed. This is probably less than 10% oi the total production and decreasing. Propagation is by natural seed production and spreading. b. cultzvation for home* use in the fiel.1 generhlly in mixed croppings with other food plants, or in home gardens. About 200 vegetable species are used for this purpose and yield at least 50% of tht total production. None, or very few, inputs are used and no expenses are made for seed, fertilizer, pesticides or equipment. Nearly all the seed needed is harvested by the farmer or gardener himself; a small : part is obtained from other farmers or bought from a local dealer. ,“i.. market gardening in mono-cultivation of a vegetable crop or in mixed plantings. Commercial gardening may be more or less intensive, ie. with a more or less high input of labour and acquisition of seed, fertilizer, pesticides and equipment. Market gardening with about 80 species covers 40% of the total vegetable production, but it is fast increasing and very important for the alimentation of urban populations. Seed of the more local, traditional vegetables usually comes from the farmer’s own production, but seed of th t: *international’ vegetables such as onion, tomato, sweet pepper, yhite cabbage, cauliflower, cucumber, watermelon, melon, lettuce, carrots, etc. ib, often bought from dealers who import it from well-known international seed?ompanies. It is not known exactly how much vegetable seed is imported, nor which part is locally produced for commercial purposes and which part by the farmer for his own use. A rough estimate could be that about 10% is imported, 30% comes from local commercial production and. 60% is home produced. In fact, the picture is very diverse depending on the area and the type of vegetable. Many growers buy the expensive imported seed only occasionally and harvest their own seed from the first crop for 2 to 5 generations before proceeding to seed renewal. The actual trend, buying imported or locally produced high quality seed of high yielding modem cultivars, holds the danger of ‘genetic erosion’, i.e. the loss of traditional, local cultivars, the so-called land races. These old cultivars represent a most valuable gene stock and are the basic material indispensable for future plant breeders. They ought to be collected and stocked in gene banks. 1.4 Problems of vegetable seed production in the tropics In temperate countries, the cost of the seed is small, less than one per cent of the total investment in a vegetable crop. This may be somewhat more in the tropics, but the commercial grower is willing to pay a good price for reliable seeds, yet in many cases they are not available. Why is this? The reason could be found in economic underdevelopment and a lack of good management and organization. A modem seed industry is a large scale enterprise, needing a heavy investment and many skilled people such -a plant breeders, seed agronomists and seed technologists. In most developing countries, basic food crops such as cereals and tubers receive the highest priority in’research and breeding. Vegetable breeding and seed production are given less priority than the urgently needed energy foods. Moreover, the number of vegetable species is so large that the costs of research and the establishment of a seed industry are excessively high and not in balance with the relatively small costs of seed importation. Only a few countries in the tropics and subtropics have developed an important vegetable seed industry and have introduced legislation concerning seed pr,oduction and trade; India, Taiwan, Brazil. Other countries such as Pakistan, Egypt, the Philippines, Sri Lanka, Thailand, Mexico and Kenya are building up their own seed industry and control agency. Holrever, in most countries in the tropics the grower depends on imported, good quality b.1.t genetically not well adapted seed supplied by foreign seed companies and on uncertified locally produced, often v2i-y poor quality seed of local vegetable types. In most countries there is no legislation for seed production and no control agency to protect the producer and the grower. In this bulletin, directions will be given to extension workers, vegetable growers and seed dealers on how to obtain *he best quality irnported seeds and how to improve the quality of the locally produced seeds. It is by no means a guide for large scale commercial seed production. 2. CLIMATIC INFLUENCES . ‘. 2.1 Climate and vegetable growing Each species or cultivar (variety), has its own special ecological requirements concerning soil, water, temperature, hght and daylength. Unlike vegetables in temperate areas, those growing in the tropics ard almost exclusively cultivated in the open. Apart from soil type and availability of water, the climate determines wheth- er or not a given species can be grown successfully. The most important climatic factor is temperature, We often distinguish between temperate (European-type) vegetables such as lettuce, white cabbage, carrots, cauliflower and French beans, and tropical vegetables such as kangkong, bitter gourd, yardlong bean, okra and hot peppers. It would be better to call these two groups cool-season vegetables and hot-season vegetables. For instauce white cabbage is a cool-season vegetable which is extensively grown not only in the temperate zone but also in cool parts of the tropics, i.e. in mountainous areas and elsewhere during the cool season. Tomato, sweet pepper and eggplant, on the other hand, are warm- season vegetables, well-known in the tropics but also widely grqwn in temperate areas, either the whole year round in glasshouses, or only du&g the summer months in the open. Some species have a very wide temperature range: Chinese cabbage, sweet corn, cucumber, radish, spinach beet and bunching onion are grown in areas with diurnal temperatures varying from 15 to 35’C. Other species have a narrower temperature range. Spinach, for instance, requires a diurnal temperature between 10 and 20°C, while amaranth, its tropical counterpart, performs best at temperatures above 3O’C. Table 1 gives an indication of the most suitable vegetable species for different climates, Daylength influences flowering of plants, As far as vegetable production is con- cerned, it is important for those types which are cultivated for the fruits: solana- ceous species, cucurbits, leguminous vegetables, CaulifZower, broccoli, okra, roselle and sweet corn (see Table 2). For a successful cultivation of these vegetable species in the tropics, the daylength reaction ought to be either short-day or neutral. It is an Bdvantage for leaf vegetables growing in the tropics if they react not too strongly to short days. Early flowering may decrease the total yield of leaves, it lowers the quality of the produce because it is mixed with inflorescences and hampers the harvest. Onion cultivars grown in temperate areas during the summer months require a long day for bulbing, but cultivars used in the tropics do bulb in short days. Onions have been noted as day neutral in.Table 2, since the seed production of the bulbed onion is mainly enhanced by a cold period, regardless of the daylength. It must be noted that some vegetable species have evolved into cultivar groups with different daylength reactions. For example, okra and yardlong bean exist as short-day, day neutral and long-day cultivars. Daylength has serious consequences for seed produc- tiqn, as will be shown in the next paragraph. Air humidity can be very high in the hot, humid tropics (> 80%) even during the dry season. iMost tropical leaf vegetables and some other species such as chayote, wing bean and yardlong bean seem to perform better at a high relative humidity. Table 1. Climatic areas of the main vegetable types propagated by seed for cultivation in the open; mean day temperatures suitahie for (possibly irrigated) cultivation (++), possi- ble (+), difficult (-), not suitable (--). ‘common name tropics sub tropics temperate - --- -- !&J humid savanna mountain summer winter summer tropics hot cool areas season season 2%35'C 30-40°C ZO-3O'C 15.30°C 25.40°C 15.25°C 15.25°C 1. Solanaccor~ vegetables sweet pepper hot peTper tomato eggplant 2. Cucurbits wax gourd watermelon melon cucumber pumpkin, squash bottle gourd loofah bitter gourd snake gourd 3. Leguminous vegetables pigeon pea sword bean hyacinth bean soybean yam bean lima bean mung bean common bean pea wing bean broad bean yardlong bean, asparagus bean, climbing cowpea voandzou 4. cruciFcrs Chinese cabbage (pakchoi) Chinese cabbage (petsai) African cabbage turnip mustard borecole, kale cauliflower broccoli white cabbage radish + tt + i-b tt + ++ ++ i-l- t-t ++ + + ++ + ++ ++ ++ . . i-k . . ?4 + ++ . t + + + + I-+ it + ++ ++ + + + ++ ++ ++ ii i-t i-t ++ 4-J- + tt ++ ++ . . 4-i . . U ++ u + U + + + + + ++ ++ ++ tt t U i-t ++ i+ t + ++ + ++ ++ + ++ tt + + + + + + + + ii tt it + ++ + ++ ++ t-k ++ ++ + ++ + + ++ +t ++ ++ + t + + + t + it + + + U i-l- + t+ + + U it ++ + # ++ + ++ ii ++ ++ t+ tt + + ++ U t+ ++ + + ++ + + + ++ + U U + t ++ t+ U +t + + + U + + t t t ++ t . . . . . . . . . . + . . +I- +I- * . . . . + i-9 + ++ it +t ++ t U ++ . . . . .' + + . . . . . . . . . . . . . . . . . . i-k ii . . 4-t . . . . t ++ + t+ U ++ U + +t ++ -. ,.. common name 5. Tropical leaf vegetables amaranth baseila jew’s mallow kangkong nightshade Unum New Zealand spinach 6. Various hot-season vegetables okra roselle sweet corn 7. Various cooLs;ason vegetables onion Japanese bunching o.tion leek celery asparagus qxnach beet garden beet endive -- tropics subtropics temperate low humid savanna mountain summer winter summer tropics hot cool areas SCaSOZl season 28-35°C 30.40°C 20.30°C 1530°C 25-40°C 15-25°C 1525°C ,, /’ I- ++ + 4-i + ii ++ ++ ++ ++ ++ ++ ++ -_ + + + - . + - _ + - - + + 8’ + / - . + U - . - _ - _ + e _ ii ++ + 4- +A ++ + ++ ++ u *k . ‘+ -- ++ + + + ii + ++ + + + U + ++ -- + + +,’ - + - + , + + + -t + 3 + ++ + + ++ / t4 ++ + + + ii + u ++.Y + + + u + ++ ++ ii . ++ c ++ . ++ + U s I-+ ++ U ++ U ++ -I-+ ++ i-b ++ ;’ ++, u carrot lettuce spinach However, a high air humidity is a h -i lcap for most vegetable species, h&cause it favours the deveiopment of pests ally obtained with irrigated ve x4 ‘Id dise+es. Therefare, the best resuj& are gener- tables fn arid regions (R.H. < 60%). ,/“’ Other climatic factors @&fall, wind, radiation), although important in relation to cultivation practices, will not be discussed here. I” ,,.’ 2.2 Climate and seed production “.” i’ The same c!&atic factors which influence the growi& of vegetables also act on seed production, often very pronounced. Since it