ChileanJAR

Mean seed weight (MSW) is a relevant trait in grass pea (Lathyrus sativus L.) commercialization because large grains are preferred in Western markets. Extending the knowledge on its mode of inheritance among large-seeded types would be useful in breeding programs, and therefore it was the objective of this work. A broad range of MSW is found in grass pea, starting at about 30 mg. Three lines (LS-97, LS-8, and LS-2026) within the large-seeded group but with significantly different MSW (179, 360 and 470 mg, respectively), were crossed in a complete diallel. Part of the F₁ seed was sown and the remainder was stored. F₁ plants from each cross were allowed to produce F₂ seed and some were backcrossed to their respective parents. Parents, F₁, F₂, and backcross populations were grown in the field in 2006. MSW was obtained from single plants in each population. No difference was observed between reciprocals of crosses LS-97 ´ LS-8 and LS-8 ´ LS-2026; therefore, data from reciprocals were combined, assuming nuclear inheritance. However, F₂ segregating population from cross LS-97 ´ LS-2026 and its reciprocal gave significantly different means, suggesting cytoplasmic inheritance. Consequently, F₂ and backcross data were handled separately to calculate heritability. Parent lines with high MSW, particularly LS-2026, had greater variances, raising the estimate of environmental variance. Broad sense heritability estimates for MSW were 0.50 and 0.32 for crosses LS-97 ´ LS-8 and LS-8 ´ LS-2026, respectively, and 0.23 and 0.24, for cross LS-97 ´ LS-2026 and its reciprocal, respectively. Narrow sense heritabilities were 0.42 and 0.28, and 0.15 and 0.22, respectively. In all crosses, the genetic effects were predominantly additive, predicting a good response to selection for increased MSW in early segregating generations. Thus, the prospects to improve MSW in large-seeded grass peas are auspicious.