Effect of genotype and environment on pod wall proportion in white lupin: consequences to seed yield

One means of increasing seed yield in white lupin may be the modification of the harvest index in the reproductive compartment by a reduction of the proportion of pod walls. Genetic and environmental effects on the pod wall proportion and yield components were evaluated. Thirty-five genotypes of spring-sown material were sown in 6 different locations across France in 1996 and 1997, accounting for a total of 10 site x year combinations. The existence of a genetic variation for the pod wall proportion among studied genotypes was demonstrated (0.26-0.34). Highly significant genotypic differences for the pod wall proportion, seed number per pod, seed weight per pod, mean seed weight, flowering time, and seed yield were observed among lupin genotypes. The heritability of pod wall proportion was moderate, the phenotypic correlation between this character and seed yield was significant and negative, and the genetic correlation was high and negative. The environmental variance contributed a major part of the total variation. The genotype x environment effect for the pod wall proportion was small, which suggests that the selection of genotypes with low and stable pod wall proportion in different environments will be possible. The strong negative genetic correlation between pod wall proportion and seed yield supports the feasibility of using the character as a selection criterion for a higher seed yield.