ICRISAT Archival Report 2006 - The seedlings of success in the ...

Tomatoes
Tomatoes are the most popular vegetable in the Sudano-Sahel. During the rainy season (June-September) tomato
fruit set is very poor. We hypothesized that this might be due to the high night temperatures during this period.
Previous research had studied the effect of high day/night temperature regimes on fruit set, finding that these
regimes drastically reduced fruit set (Abdul Baki, 1991). However there was little information on the effects of high
night temperatures alone (with day temperatures kept constant).
The performance of ‘Xina’, a tomato variety that sets fruit in the rainy season, was compared with that of a rainy
season “sensitive” variety, varying only the night temperature (comparing 34°/29°C versus 34°/18°C day/night). The
results (Table 2) support the hypothesis that the high night temperatures that prevail during the rainy season are
responsible for the low fruit set of tomatoes during that season.
Xina had a higher fruit yield at higher night temperatures because it had more flowers and a higher percentage fruit
set as compared with the Negev variety
Table 2. Effect of two day/night temperature regimes on yield, number of flowers per plant and percent fruit set for
rainy-season tolerant versus sensitive tomato varieties (‘Xina’ and ‘Negev’). The values for the high day/high night
temperatures are means of hourly temperatures in a screen house. Low night temperatures were obtained by
transferring pots each night into an air-conditioned room.
Temperature
regime
Variety
34°/29°C
34°/18°C
Yield
(kg/plant
Flowers/plant
(No.)
Fruit Set
(%)
Yield
(kg/plant)
Flowers/Plant
(No.)
Fruit Set
(%)
Xina 2.24 672 17 4.72 608 67.9
Negev 1.28 287 8.2 4.13 424 61.0
The fruit quality of Xina however is very poor. It is a segregating variety with large variability in fruit size and
shape. This allowed selection within the variety that markedly improved the quality of Xina fruit (Pic.3).
Selection within the Xina population
resulted in larger and uniform fruit of
superior quality
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