Abstract

The relatively high seed coat proportion of the narrow-leafed lupin reduces its economic value. This character has been shown to be affected by seed weight, and this limits the use of seed coat proportion as a selection criterion. We examined the variation for seed coat specific weight, a potential alternative selection criterion, and tested its relationship with seed coat proportion and seed weight. Seeds were sampled from mainstem pods of 14 winter-sown genotypes of Lupinus angustifolius L. grown at 4 southern Chile sites over 2 years. Seed coat specific weight had an overall mean of 30.1 mg/cm2. Highly significant genotypic effects were found (range 28.9-32.1 mg/cm2). The ranges for sites and years were 29.1-31.1 and 28.9-31.2 mg/cm2, respectively. Genotypes interacted significantly with years, but not with sites. Broad-sense heritability was 0.59, a value that predicts a good response to selection for this character. Seed coat specific weight was weakly correlated (rph = 0.11*) with seed coat proportion, and was not associated with mean seed weight. Seed coat proportion was negatively correlated with mean seed weight (rph = -0.75***) and had high broad-sense heritability (0.95). The correlation between seed coat specific weight and a theoretical seed coat thickness, calculated under the assumptions of equal mass density of seed coat, cotyledons, and embryo, and a spherical-shaped seed, was r = 0.14*. Phenotypic and genotypic correlations between seed coat specific weight and number of seeds per pod were 0.41 and 0.84, respectively. Our results indicate that selection for low seed coat proportion will lead to larger seeded genotypes, but will not reduce seed coat specific weight. Selection for low seed coat proportion after crosses would presumably be effective in reducing seedcoat specific weight if all segregating materials were uniformly large seeded, but that scenario is unrealistic. The evidence presented here suggests that selection for low seed coat specific weight (or measures correlated with it) in segregating populations will be necessary in order to increase the proportion of higher value kernels in seeds and to improve the economic yield of lupins.