Dry matter and nitrogen accumulation during pod wall development of white lupin genotypes differing in proportion of pod walls

Pods of white lupin are characterized by a high proportion of pod walls in the pod mass at maturity. Genotypic variation in pod wall thickness at maturity and in proportion of pod walls has been described in this species. The objective of this study was to describe the pod and seed development in two ecotypes and one cultivar of spring-sown white lupin differing in proportion of pod walls, and to estimate the precise stage of development when the differences in pod wall dry matter among genotypes are first observed. The nitrogen content was also determined during the pod development of three genotypes, LA356, E084 and Lublanc were grown in the field in the UK and France in 1998 and 1999. The duration of pod and seed development was similar among genotypes and environmental conditions. Proportion of pod walls by dry weight at maturity were 0.21-0.23 for LA356, 0.27-0.28 for E084 and 0.30 for Lublanc. The ecotype with the lowest proportion of pod walls accumulated less dry matter in the pod walls than those with the highest proportion. Variation in pod wall dry matter per seed between genotypes was observed early during the pod development (300 degrees Cdays from flowering) and it was maintained during all pod development. No significant differences were observed for the total nitrogen content at maturity among genotypes with high and low proportion of pod walls.