Among tomato varieties there are noticeable differences regarding capacity to set fruits under extreme temperature conditions. Cases have been described in which lines selected to set under low temperature conditions, also set fruit better under high temperature conditions. Examples are Farthest North and Severianin (Tarakanov et al., 1978) and BL 6807 Sub Arctic Plenty (Harris, 1972; El Ahmadi and Stevens, 1979). It is therefore possible that conversely, varieties selected to set fruits under high temperature conditions might set fruit well under low temperature conditions.
In order to prove this hypothesis, 10 lines from the Shanhua AVRDC Seed Laboratory in Taiwan reported to possess heat tolerance, were cultivated during the winter and the summer. Average minimum and maximum temperatures during flowering months were 8.7 +/- 2.4 and 22.6 +/- 3.0 in the winter and 20.6 +/- 3.2 and 33.7 +/- 4.1 in the summer.
Under winter conditions none of the observed lines were able to set normal fruit. Fruit which did set (Table 1) were much smaller than normal, rugose, puffy, with no seeds or gel. These "pseudofruits" ultimately ripen, but require much more time than normal fruits.
Under summer conditions (Table 1) normal fruits are produced; setting is generally good although there are differences among experimental lines. 1104-0-0-29-1-0 is the most promising improvement line as it is not only heat tolerant, but its fruit has almost commercial acceptibility.
Literature cited:
El Ahmadi, A.B. and M.A. Stevens. 1979. Genetics of high temperature fruit set in the tomato. J. Amer. Soc. Hort. Sci. 104:691-696.
Harris, R.E. 1972. Three new sub-arctic type tomatoes: "Early Sub-Arctic," "Sub-Arctic Midi" and "Sub-Arctic Plenty." Can. J. Plant Sci. 52:119-120.
Tarakanov, G.I., S.A. Dodevar, L.G. Avakimova, E.N. Andreeva, and E.A. Sisina. 1978. The ways to increase fruit-setting in tomatoes under high temperatures. Brezhnev, D.D. (ed.) Genotype and Environment Inbreeding Greenhouse Tomatoes. Leningrad, USSR p. 123-129.
Table 1. Fruit setting characteristics under winter and summer conditions.
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Winter
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AVRDC Accession Setting Hollowness 0 cm.
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CL 1131-0-0-7-2-1 Fair Severe 3-4
CL 1131-0-0-13-0-1 Good " 2-3
CL 1131-0-0-13-0-6 Good " 2-3
CL 1131-0-0-38-4-0 Fair " 2-3
CL 1131-0-0-43-4-12 Very bad Moderate 2-3
CL 1131-0-0-43-8-1 Bad Severe 1-2
CL 1131-0-0-43-10-1 Bad " 1-2
CL 143-0-10-3-0-1-10 Bad " 2-3
CL 9-0-0-1-3 Bad " 2-4
CL 1104-0-0-29-1-0 Good 4-5
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Summer
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Fruit
weight Fruit
Setting Hollowness 0 cm. (grs.) seeds
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CL 1131-0-0-7-2-1 Very good Absent 5 59 > 30
CL 1131-0-0-13-0-1 Good Slight 4-5 39 < 10
CL 1131-0-0-13-0-6 - -- --
CL 1131-0-0-38-4-0 Good Absent 4-5 44 > 20
CL 1131-0-0-43-4-12 Fair Absent 3-4 32 > 30
CL 1131-0-0-43-8-1 Very good Absent 4-5 37 > 30
CL 1131-0-0-43-10-1 Good Absent 4 26 > 20
CL 143-0-10-3-0-1-1 Good Absent 4-5 38 > 200
CL 9-0-0-1-3 Very good Absent 5-6 53 > 20 ft
CL 1104-0-0-29-1-0 Good Slight 6-7 93 > 20
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