Genotype–Environment Analysis of Parameters Describing Water Uptake in Natto Soybean

The amount of water absorbed following a defined soaking period has been studied in natto soybean [ Glycine max (L.) Merr.], but there are no reports of studies of the rate or rapidity of water uptake. This study was conducted to examine the suitability of several water uptake parameters, which define the speed and amount of water absorbed, for analysis of variance and to determine the extent of genotype, environment, and genotype × environment interaction effects on water uptake parameters. Two larger‐seeded checks and 14 natto lines were grown at six locations in 1996 and 1997. Water uptake observations were taken at 0, 1, 3, 6, and 24.5 h using seed from individual plots. The exponential rise to a maximum equation, Y = a [1 − exp(− bX )], was fitted for each plot. The parameters a at 16 h (a16) and b , best fit the assumptions for analysis of variance. Genotype, year × location, genotype × year, and genotype × location × year effects were significant for these parameters. Location effects were significant for a16 but not for b Year and genotype × location effects were not significant. In this study, genotype × environment effects were relatively unimportant, while the main effect of genotype was more important. The b parameter provides additional information compared with the use of a16 alone. Heritability estimates for water uptake parameters (a16, H = 0.36 ± 0.16; b , H = 0.42 ± 0.46) were low to moderate on a plot basis. It seems possible to select for both rapid and high final water uptake in natto soybean.