Effects of Temperature and Photoperiod on Phenological Development in Three Genotypes of Bambara Groundnut (Vigna subterranea)

Factorial combinations of four photoperiods (10, 11·33, 12·66 and 16 h d -1 ) and three mean diurnal temperatures (20·2, 24·1 and 28·1°C) were imposed on nodulated plants of three Nigerian bambara groundnut genotypes [ Vigna subterranea (L.) Verdc., syn. Voandzeia subterranea (L.) Thouars] grown in glasshouses in The Netherlands. The photothermal response of the onset of flowering and the onset of podding were determined. The time from sowing to first flower ( f ) was determined by noting the day on which the first open flower appeared. The time from sowing to the onset of podding ( p ) was estimated from linear regressions of pod dry weight against time from sowing. Developmental rates were derived from the reciprocals of f and p. In two genotypes, 'Ankpa 2' and 'Yola', flowering occurred irrespective of photoperiod and 1/ f was controlled by temperature only, occurring sooner at 28·1 than at 20·2°C. The third genotype, 'Ankpa 4', was sensitive to temperature and photoperiod and f was increased by cooler temperatures and photoperiods > 12·66 h d -1 at 20·2°C and > 11·33 h d -1 at 24·1 and 28·1°C. In contrast, p was affected by temperature and photoperiod in all three genotypes. In bambara groundnut photoperiod-sensitivity therefore increases between the onset of flowering and the onset of podding. The most photoperiod-sensitive genotype with respect to p was 'Ankpa 4', followed by 'Yola' and 'Ankpa 2'. There was also variation in temperature-sensitivity between the genotypes investigated. Evaluation of bambara groundnut genotypes for adaptation to different photothermal environments will therefore require screening for flowering and podding responses. Copyright 1994, 1999 Academic Press