Genotypic and environmental effects on pod wall proportion and pod wall specific weight in Lupinus angustifolius

Fourteen winter-sown genotypes of Lupinus angustifolius L., comprising most of the Western Australian cultivars released since 1986, were studied over 2 years at 4 southern Chile locations. Pod wall proportion, pod wall specific weight, seed number per pod, mean seed weight, seed weight per pod, wall weight per pod, and mean pod weight were measured, separately sampling pods from the mainstem and pods from branches. The 2 pod positions differed significantly for all characteristics except wall weight per pod. Lower coefficients of variation and greater heritabilities for both pod wall proportion and pod wall specific weight were achieved with a sample of pods from branches than with a sample from the mainstem. The ranges for pod wall proportion and pod wall specific weight were small (31.8–35.8% and 27.0–34.7 mg/cm2, respectively); however, highly significant genotypic effects were found for both characters. Heritability estimates were moderate for pod wall proportion (0.27 and 0.44 for pods from mainstem and branches, respectively) and moderate to high for pod wall specific weight (0.56 and 0.61, respectively). Pod wall proportion and pod wall specific weight were significantly correlated, more so at the genetic level ( r g = 0.83 and r g = 0.76 for pods from mainstem and branches, respectively) than at the phenotypic level ( r ph = 0.57 and r ph = 0.60, respectively). Pod wall specific weight was closely associated with wall weight per pod, meaning that larger pods call for thicker pod walls. Accordingly, selection for low pod wall specific weight in a breeding program could lead to light pods. Correlations with mean seed weight indicate that this trait could decrease as well.