Effects of seed size and maturity on the growth and yield of faba bean (Vicia faba L.)

The importance of seed size and flowering time to yield in faba bean has not been well defined for many of the faba bean growing areas of southern Australia. The objective of this work was to examine the relative importance of these traits to yield of dryland faba bean at 2 sites in South Australia. Grain yield, seed growth rate, the partitioning of dry matter to the seed, and water use efficiency for dry matter production and yield of faba bean cultivars differing in seed size and maturity were measured. Early-, intermediate-, and late-flowering accessions in each of 3 seed size classes, large (>1200 mg/seed), medium (800-1200 mg), and small (<800 mg), were grown at the Waite Institute (623 mm average annual rainfall) and Charlick Experiment Station (509 mm). A small-seeded and intermediate flowering cultivar, Fiord, which is well adapted in South Australia was also included. Dry matter production and grain yields at the Waite Institute were higher than at Charlick and the difference tended to be greater in the large-seeded accessions. Average yields at the 2 sites were about 400 g/m 2 and were not consistently related to seed size, although the highest yielding accession at both sites was large-seeded. Among the small- and medium-sized seed accessions, the early-flowering accession yielded more than late-flowering accessions, but among the large-seeded accessions there was no relationship between flowering time and yield. Although there were significant differences between accessions and sites in individual yield components, yield was not significantly correlated with any particular component. There was strong compensation between seed number and seed size and high yields were obtained from a range of seed sizes. In contrast there was a positive relationship between dry matter production and yield. Partitioning of dry matter during pod filling and harvest index differed little between genotypes. Yield was therefore related to biomass accumulation, and whether this was partitioned between a small number of large seeds or a large number of small seeds was not an important factor.