Hacia dónde va la mejora genética?
27 de septiembre de 2004
Giulio Bile, Giulio.Bile@seminis.com, genetista de tomate de Seminis, analiza, en el texto expandido, qué busca la mejora genética actual en tomate para industria. El trabajo, que está en inglés, forma parte, traducido a español, del Compendio sobre tomate que edita Ediciones de Horticultura, www.horticom.com, en noviembre 2004.
Goals of the processing tomato breeding
Plant Breeder, Seminis Vegetable Seeds Italy
History of processing tomato - It is well known that the tomato has its origin in the tropical and sub-tropical areas of South America (Perù and Ecuador) and that, therefore, its consumption in Europe started after XV Century in Spain. At the beginning the tomato wasn't considered a desirable food, due to its bad flavor too rich in solanina. Than during the XVII century, the new selected varieties coming from Mexico to Spain were more desirable; they were consequently widespread through Arabian from Spain to Italy (Sicily) and then to the rest of Europe always for Fresh Market consumption. In fact, the first canneries for processing tomato were opened about 100 years later, after the discovers of Appert and Pasteur, basic principles for the cannery food. In Italy the first cannery was established in Torino by Francesco Cirio in1857 (P.L. Longarini "Il passato del pomodoro" Nov. 1998 Silva Editore).
Actually the leading WW producers (based on tonnage) are: California (37%), Italy (16%), China (8%), Turkey (6%), Spain (6%), Brazil (4%). So, regarding the Mediterranean Bacin the market size is referring to 280.000 Has with a production around 10 millions tons and with a seed value about 25 millions Euro.
Objective - The purpose of the breeder on processing tomato market is the obtaining of new hybrids better than the leading varieties in terms of both quantitative and qualitative characteristics according to growers, canneries and market needs. It usually takes at least 5-6 years to develop and test a variety before its merits are determinate. If the plant breeder starts now working on today's needs, he is starting already 5-6 years late. He should be looking at the future, not at the present.
Briefly following are the main key points in processing tomato breeding activity, which help the breeder to achieve his objective: a) Diversity of existing types; b) Uses and destinations of the tomato fruits; c) Environments and cultivation techniques; d) Pathology, Biotechnology and Fruit Quality Lab contributions to the breeder; e) Future needs.
a) Diversity of the existing types - It is important to work with large populations in order to amplify the genetic variability, to create new germplasm, to make back cross for the integration of the desirable genes into breeding lines and finally to make successful hybrids. Of course a larger genetic distance between parent lines to be crossed, improve the positive heterosis effect in the hybrid condition. In the main WW processing tomato areas like California, Italy and Spain, almost 100 % of the varieties in the market are hybrids. Also In other important areas for processing tomato like Turkey, where the OP (Open Pollinated) varieties (mainly Rio Grande and Rio Grande type) were 60 % of the total till few years ago, now, due to the enormous differences in terms of quality-quantitative performances, they are converting quickly to the hybrids. In fact, in a couple years the percentage of the hybrids versus OP moved from 40% to 70 % of the total, despite the consistent difference on the seed price.
The tomato varieties developed for canneries show big differences with the tomato varieties developed for Fresh Market. For this reason the breeding strategies used for both breeding programs are quite different (see Table 1).
Processing tomato / FM tomato
Main Breeding Differences
Processing tomato Fresh Market tomato
- open field - mainly GH
- one time harvesting - several times harvesting
- concentrated set - no concentrated set
- determinate plant habit (sp gene) - indeterminate plant habit
- jointless (j- gene) - mainly jointed
- uniform fruit color - mainly green shoulders fruit
- not too big fruit size on pear segment - bigger pear type is desirable
- mechanical harvest - hand harvest
- fruit quality for canneries - fruit quality for fresh market
(brix, color, viscosity, pH, pelability) (color, LSL, brix)
- main areas in Italy: - main areas in Italy:
Poe Valley, Puglia (Foggia) Sicily, Lazio
- main area in Spain: - main area in Spain:
- main area in Turkey: - main area in Turkey:
- Xanthomonas campestris - Botrytis cinerea
- Alternaria solani - Cladosporium fulvum
Fungi: Verticillium, Fusarium, Pyrenochaeta lycopersici, Ph. infestans
Virus: TSWV, TMV, TYLCV.
Bacteria: Pseudomonas syringae pv. tomato.
Nematode: Meloidogyne spp. (incognita, hapla, arenaria, javanica).
b) Use and destination of the tomato fruits - In the last years the processing tomato breeders developed many different tomato varieties, in terms of plant habit, foliage and root system, shape and size of the fruits, diseases resistance and so on. A good example of it is the case of S. Marzano open pollinated (OP) variety; in fact, several years ago the canneries in the South Italy were using it for whole peel tomatoes in cans; this S. Marzano OP variety was characterized by good fruit quality, but with indeterminate plant habit, large cylindrical pear type, soft fruit, jointed stem, late cycle, no diseases resistance. Now almost 100% of the varieties used for peeling are hybrids, characterized by determinate plant habit (sp gene, single recessive gene responsible for self pruning) smaller fruit size (no more than 90 grams/each good for half kilo can too), more concentrated set and firmer fruits suitable for mechanical harvest, no stems, resistant to the main diseases (Verticillium, Fusarium, Pseudomonas syringae pv. tomato, Nematode, TSWV), more tolerant to cold temperature for early season and to cracking for high humidity areas and so on.
Anyway, as reported in the Table 2, the processing tomato markets are divided in three main segments: square, round or blocky type (77%), pear (21 %) and cherry (2 %). The square/round/blocky type is used mainly for paste and dicing, but also for ketchup, tomato juice and powdery; it should be characterized by firm fruits with very good color, 70-90 grams/weight of each, thick wall, good fruit quality; pear type is used mainly for peeling and sundry; the fruit size should be no more than 90 grams, good fruit quality and, of course with a good pelability; the cherry type is used mainly for whole cherries in half kilo's can; in this case the fruit size should be no more than 10-15 grams, because generally the canneries use about 20 fruits plus tomato juice for each can. In some areas (mainly in South Italy), if the market price is interesting, they use the same cherry processing types for Fresh Market too. This processing cherry segment actually is very small in comparison to the others, but is increasing, due to its very good flavor.
Use and destination of tomato fruits
c)Environments and cultivation's technique - In order to develop successful hybrids, it is important to know well also the environmental characteristics where the new varieties have to be included ( cold or hot conditions, dry or wet areas, short or long season, diseases pressures, clay or sandy soil etc.) and the cultivation's techniques (drip, flowing, or sprinkle irrigation system, direct sowing or transplanting, mechanical or hand harvest, single or binate rows, with or without mulching).
d)Pathology, Biotechnology and Fruit Quality contributions to the breeding. Regarding Pathology, it has always had a crucial role on the obtaining commercial competitive varieties. Disease routine tests and the possibility to use survivors from them, permit to go faster on the introgression of diseases resistant genes into strategic inbred lines. Most of the commercial varieties are already resistant to some Fungi (Verticillium dahliae and Fusarium oxysporum f. sp. lycopersici and their different races, Alternaria alternata f sp lycopersici, Stemphilium solani), Bacteria (mainly Pseudomonas syringae pv tomato race 0), Virus (TSWV, ToMV), Nematode (Meloidogyne spp.). New diseases resistances genes to other Fungi (Leveillula taurica, Phytophtora infestans, Phyrenochaeta lycopersici, Fusarium oxysporum f.sp. radicis lycopersici, Alternaria solani), Bacteria (Xanthomonas campestris pv tomato), Virus (CMV, TYLCV, PVY) are going to be included in inbred lines in order to obtain resistant processing tomato hybrids in the coming years (Table 3).
Processing tomato breeding objectives
V = Verticillium
F = Fusarium
ASC = Alternaria Stem Canker
ST = Stemphilium
CR = Corky Root
FCRR = Fusarium Crown and Root Rot
EB = Early Blight
PM = Powdery Mildew
LB = Late Blight
B. Speck = Bacterial speck
B. Spot = Bacterial spot
TSWV = Tomato Spotted Wilt Virus
TYLCV = Tomato yellow leaf curl
CMV = Cucumber Mosaic Virus
ToMV = Tomato Mosaic Virus
The contribution of the Biotechnology to the breeding activity is relatively more recent, but it is clear its strong potentiality. The use of molecular markers in linkage with particular characters, for example, gives the opportunity to the breeder to go faster on his activity. In fact this technique permits to recognize the resistant plants already at the cotyledon/first true leaf stage (before transplanting), instead of waiting the end of the cycle with the pathogen (see the case of Nematode and of the Pyrenochaeta lycopersici). Moreover the molecular markers permit to identify and, eventually, to protect hybrids and/or breeding lines. Regarding the embryo rescue, this technique permits to overcome the incompatibilities in the interspecific crosses. One more branch of Biotechnology is the use of transgenic techniques; in some cases the introgression of some particular genes into plant genome by genetic transformation approach could support and help the traditional breeding in term of results and time. A long term objective of the use of transgenic methodology could be the obtaining of genetically modified tomatoes as potential vaccines against a range of diseases like hepatitis B, cholera, Norwalk virus ("Tomato news" September 2004). Of course it does not replace the traditional breeding, but has a complementary role, and, anyway, actually the EC law prohibits the growing of the tomato transgenic varieties in Europe.
Not less important is the contribution of Fruit Quality analysis to the breeding acitivity. In the last years the main WW markets (California, Italy, Spain) are paying more and more attention to the fruit quality on processing tomato. Beside the historical qualitative traits like color, brix, viscosity and pH, the level of Lycopene contents is becoming crucial. Lycopene is one of the several dietary carotenoids found in tomato and other fruits, (i.e. Watermelon, Papaya, Grape Fruit). The natural Lycopene in tomatoes becomes more readily after the heat processing. In fact processing tomato has received excellent documentation from the medical profession as the best source of Lycopene for human source against heart disease (Sesso et. Al Am J Clin Nutr 2004; 79: 47-53) and against cancer, in particular using whole tomatoes products (Boileau et al. J. Natl Cnacer Inst 2003; 95 1578-86). Moreover, also in pharmacy segment, some of the multivitaminic supplements are now interested on adding Lycopene to their formulae.
It is important to underline that pathology, biotechnology and fruit quality analysis are powerful tools for plant breeding in order to go faster on obtaining successful hybrids, but never can substitute the traditional breeding methods.
e) Future needs: In recent years the breeding on processing tomato made a lot of progress in terms of both horticultural characteristics and diseases resistance. Some genes introgression in the cultivated varieties changed the cultivation techniques and permitted to grow tomatoes also in environments characterized by different abiotic and biotic stresses. Some good examples of the these genes integrated into commercial hybrids are: sp gene, self pruning gene responsible for determinate plant habit character; pto gene, responsible for of the resistance to Pseudomonas syringae pv. tomato; sw-5 gene, responsible for the resistance to TSWV, very common virus in South Europe (mainly South Italy), South America (mainly Argentina, Australia); j- gene, responsible for the jointless character, which means no stems on the fruits harvested by machine, and so on.
For the future, on the basis of the market, grower and cannery requirements, and on the basis of available germplasm, the breeder should put his efforts to the improvement of agronomic traits, diseases resistance, fruit quality and healthy benefits. Some example are reported in the Table 4.
Processing tomato needs
In a few words the processing tomato breeder has to be continuously updated on the market requirements, on the growers problems and on the cannery needs; on the basis of them he has to set up now the right breeding strategies in order to develop successful hybrids to be commercialized in the future.