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Abstract
The relationships between photosynthetic rate, yield, and yield components of forcing tomatoes (Lycopersicon esculentum Mill., cvs. Tuckcross V and Tuckcross 533) under variable lighting and spacing were studied during the dark winter of 1972-73. Yield and its components were all highly and positively correlated with both cloudy-day (90-110 W/m2 light intensity) and sunny-day (200 W/m2 or higher) photosynthetic rates. The rate-yield relationship remained nearly constant irrespective of the predictor variable. Better linear response of yield and its components to cloudy than to sunny-day photosynthetic rate was observed. Photosynthetic rate accounted for more than 60% of the yield variation.
Abstract
Photosynthetic and yield responses of tomato, Lycopersicon esculentum L., ev. Tuckcross V and Tuckcross 533 supplemental lighting and spacing were studied during the unusually dark winter of 1972–73. Supplemental lighting and wide spacing increased total flowers, % fruit set, fruit size, and total fruits/plant. and contributed to greater early and total fruit yields. The increases were related to increased apparent photosynthetic rate and efficiency. Supplementary top lighting (184 W/m2) increased fruit weight/plant 1107 g/plant (89%) over natural lighting for an increase of 6.0 g/plant for each watt/m2. Supplementary top + side lighting (368 W/m2) increased fruit weight 2853 g/plant (121%), an increase of 7.7 g/plant for each watt/m2.
Maximum fruit yield/plant was obtained with top + side lighting at a spacing of 50.8 × 41 cm in a staggered double row bed. Plant spacing of 38.1 × 41 cm with maximum lighting gave greatest yield/unit area. Photosaturation was not attained bv supplementary lighting.
There is a growing interest by consumers to purchase fresh tomatoes with improved quality traits including lycopene, total soluble solids (TSS), vitamin C, and total titratable acid (TTA) content. As a result, there are considerable efforts by tomato breeders to improve tomato for these traits. However, suitable varieties developed for one location may not perform the same in different locations. This causes a problem for plant breeders because it is too labor-intensive to develop varieties for each specific location. The objective of this study was to determine the extent of genotype × environment (G×E) interaction that influences tomato fruit quality. To achieve this objective, we grew a set of 42 diverse tomato genotypes with different fruit shapes in replicated trials in three locations: North Carolina, New York, and Ohio. Fruits were harvested at the red ripe stage and analyzed for lycopene, TSS, vitamin C, and TTA. Analysis of variance (ANOVA) revealed that there were significant differences (P < 0.05) among tomato genotypes, locations, and their interaction. Further analysis of quality traits from individual locations revealed that there was as much as 211% change in performance of some genotypes in a certain location compared with the average performance of a genotype. Lycopene was found to be most influenced by the environment, whereas TTA was the least influenced. This was in agreement with heritability estimates observed in the study for these quality traits, because heritability estimate for lycopene was 16%, whereas that for TTA was 87%. The extent of G×E interaction found for the fruit quality traits in the tomato varieties included in this study may be useful in identifying optimal locations for future field trials by tomato breeders aiming to improve tomato fruit quality.