Effects of photoperiod and maturity genes on plant growth, partitioning, radiation use efficiency, and yield in soyabean [Glycine max (L.) Merrill] 'Clark'

Plants of four isolines of soyabean [Glycine max (L.) Merrill] 'Clark', viz 'L71-920' (maturity gene complement e(1)e(2)e(3)), 'L80-5914' (E(1)e(2)e(3)), 'Clark' (e(1)E(2)E(3)), and 'L65-3366' (E1E2E3), were grown in short (12.25 h d(-1) natural light) and long days (12.25 h d(-1) natural light supplemented with 2.75 h d(-1) low-irradiance artificial light) from first flowering to maturity in a polythene tunnel maintained at 30/24 degrees C (day/night). Whereas there were few differences among the isolines grown in short days, in long days the dominant alleles increased crop duration, biomass and seed yield substantially. Increases in biological and economic yield were not solely a consequence of longer crop duration: the dominant alleles also increased crop growth rate and radiation use efficiency in long days (from 1.3 g MJ(-1) total radiation in e(1)e(2)e(3) to 28 g MJ(-1) in E1E2E3). Greater radiation use efficiency resulted from a relatively longer leaf area duration. better distribution and orientation of a larger mass of leaves within the canopy, and smaller partitioning of assimilates to reproductive structures. The work reveals the substantial effects of the three loci E-1/e(1), E-2/e(2) and E-3/e(3) on the response of plant growth, as well as development, to environment. Their relevance to crop adaptation is discussed. (C) 2000 Annals of Botany Company.