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 h as not been well defined for many of the faba bean growing areas of so uthern Australia. The objective of this work was to examine the relati ve importance of these traits to yield of dryland faba bean at 2 sites in South Australia. Grain yield, seed growth rate, the partitioning o f dry matter to the seed, and water use efficiency for dry matter prod uction and yield of faba bean cultivars differing in seed size and mat urity were measured. Early-, intermediate-, and late-flowering accessi ons 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 w ell adapted in South Australia was also included. Dry matter productio n and grain yields at the Waite Institute were higher than at Charlick and the difference tended to be greater in the large-seeded accession s. Average yields at the 2 sites were about 400 g/m(2) and were not co nsistently related to seed size, although the highest yielding accessi on at both sites was large-seeded. Among the small-and medium-sized se ed accessions, the early-flowering accession yielded more than late-fl owering accessions, but among the large-seeded accessions there was no relationship between flowering time and yield. Although there were si gnificant differences between accessions and sites in individual yield components, yield was not significantly correlated with any particula r component. There was strong compensation between seed number and see d size and high yields were obtained from a range of seed sizes. In co ntrast 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 t o biomass accumulation, and whether this was partitioned between a sma ll number of large seeds or a large number of small seeds was not an i mportant factor.