Comparison of soybean crop performance under tropical environment between tropical and temperate cultivars with adjusted growth duration

Considerable variation among soybean genotypes has been observed in growth and yield adaptations to tropical environments. However, the response to daylength and, hence, different growth durations are confounding factors in most studies. In this study, we conducted field experiments in a tropical environment with daylength treatment to compare the crop performance of temperate and tropical cultivars with different daylength sensitivities in terms of biomass production, seed yield, and apparent seed quality. A tropical cultivar, 'Tanggamus', which has been highly productive in Indonesia, was grown for two years in a field at Bogor, Indonesia (lat. 6.5 degrees S) with four cultivars from temperate regions. The proposed long-day treatment (LD) decreased the negative effects of short daylength in low-altitude areas on the vegetative growth and yield of soybean cultivars from temperate regions. With LD, the differences in the yield and above ground dry weight between temperate cultivars and 'Tanggamus' was less than without LD. However, the ratio of wrinkled seeds of temperate cultivars with LD was higher than that of 'Tanggamus'. There were differences in the seed-filling rate and the growth rate of pod plus seed during latter half of the seed-filling period between them, indicating a higher ability in the supply of assimilates to seeds under high-temperature conditions during the seed-filling stage. These results suggest that temperate cultivars remain to be improved in biomass and seed production under environments with higher temperatures than the climate where they are cultivated, and that 'Tanggamus' will be worth utilizing in breeding programs.
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