Differential Response of Soybean Genotypes to Photoperiod and Temperature

Abstract

Background: Soybean is a short-day crop whose growth, development and productivity are significantly influenced by photoperiod and temperature. Hence, the crop is restricted to rainy season cultivation in India. Methods: The study included fifteen soybean genotypes assessed for physiological, phenological, yield and quality traits grown under three distinct photoperiod and seasons (kharif, rabi and summer). The variation was assessed for different traits in all the three seasons. Result: Significant genetic variability was observed for all the phenological, physiological, yield and yield traits across the different seasons. Across genotypes, the oil content increased in rabi due to reduced photoperiod (11 h 20 min). There was increased SPAD chlorophyll meter reading during rabi over kharif. During summer, highest per cent increase was exhibited by chlorophyll ‘b’ followed by days to initiation of flowering, days to 50 per cent flowering, SPAD Chlorophyll Meter Reading (SCMR) and total chlorophyll when compared to kharif season. The increase in chlorophyll content could be attributed to higher temperature during summer (33.8°C) over kharif (28.3°C) due to increase in enzyme activity up to a certain level of raise in temperature (35°C) in soybean. A marked reduction in seed yield was recorded during rabi (up to 57.2%) and summer (up to 76%) compared to kharif, the usual growing season in India, primarily due to reduced photoperiod and elevated temperatures that shortened the growth cycle and adversely affected pod number, plant height and seed weight. Notably, MACS 330 showed photoperiod insensitivity for days to maturity while, DSb 34 exhibited yield stability with less seasonal reduction for different traits, suggesting their potential for cultivation under variable environments.