In many tropical and sub-tropical regions with high temperature, low fruit set decreases tomato production. In Martinique (French West Indies), the hot wet season from June to November is characterized by high temperature associated with high humidity. The purpose of this study was to find heat tolerant accessions allowing us to breed new cultivars well-adapted to the wet tropics.
Eighteen tomato varieties and populations were sown on the 15th June 1986 and 1987. Therefore, the screening of fruit setting for heat tolerance (4 repeats of 10 plants for each variety) takes place in august when temperature and humidity conditions are very severe (90% humidity, day temperature 31-32 deg. C, night temperature: 26-27 deg. C). The flowers were assumed to have "set" when their ovaries were present after their corolla dropped. Thus, this "fruit set" did not include fruit growth. The percentage of flowers setting fruit was recorded on the first three clusters of non staked main stem.
Results are presented in Table 1. The varieties of the class 3, represented by Saladette, have a high percentage of fruit set but show varied yields. The yield of Heinz 882, very susceptible to blossom end rot, is very low whereas F1Tulena and F1Capitan show a high yield. In contrast, some of the varieties of the class 1: Xina, Mienxin, F1 Nema 1200 and the segregating population Ligon (which presents some very interesting plants), remain productive although the fruit set was low. That leads to the view that fruit set is not the only criterium to screen heat tolerant varieties with a high yield. The character "fruit growth" as well as the resistance against major diseases, particularly bacterial wilt (Pseudomonas solanacearum) and root-know nematodes (Meloidogyne spp.) should also be integrated in our breeding program.
Table 1: Yield and percentage of fruit sets of tomato varieties during the hot wet season 1986 and 1987.
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Fruit set (%)^x Mean Marketable
fruit yield
Varieties Origin 1986 1987 weight (kg)^z
trial1 trial2 (g)^y
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Heinz 822 USA 3 3 NT 27 1,4
Saladette USA 3 NT NT - -
F1Tulena France NT NT 3 74 2,9
F1Capitan USA NT NT 3 73 3,1
Chico III USA 2 2 3 40 1,6
F1Sunny USA 2 NT 2 87 2,1
L 3957 Taiwan 2 NT NT - -
Walter USA NT NT 2 92 1,3
Flora Dade USA NT NT 2 75 2
F1Vista USA 1 NT 2 84 1,2
Caraibo FWI 1 1 1 68 2,4
IPA 1 Brasil 1 NT NT - -
F1Nema 1200 USA NT 1 NT 47 3,1
Xina France/Senegal NT 1 NT 25 2,6
Mienxin France/Senegal NT 1 NT 36 2,5
Lignon France/Cuba NT 1 NT 58 2,4
Liliana 72 Cuba NT NT 1 45 1,3
F1Allstar USA NT NT 1 91 1,6
F1Count II USA NT NT 1 81 1,1
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x: varieties are ranged in 3 classes according to their pecentage of fruit
set; 1, 0-40%; 2, 41-60%; 3, 61-100%.y: mean fruit weight was determined on 30 fruit, in 1987 only.
z: marketable yield was determined in 1987 only