Genetic gain in yield of Australian faba bean since 1980 and associated shifts in the phenotype: Growth, partitioning, phenology, and resistance to lodging and disease

Context: Feeding a growing human population with limited arable land requires greater crop yield that is, in turn, driven by improved agronomy, better varieties, and their synergy. Here we focus on faba bean, Vicia faba L., an under-researched grain legume for which on-farm yield in Australia has increased at 0.8 % y⁻¹ since 1990. Objective: We aimed to quantify genetic gain in seed yield of Australian faba bean varieties released since 1980, and to identify associated shifts in physiological and agronomic traits. Methods: We combined three studies: the complete historical collection of Australian faba bean varieties was grown in 1) a vintage experiment of three field trials; and 2) a pot experiment inoculated with old and new strains of Ascochyta fabae. Since most varieties were grown in a national network of trials, we 3) estimated genetic gain in seed yield and individual seed weight in 129 environments. Results: In the vintage experiment, genetic gain in seed yield varied from 0.4 % y⁻¹ to almost zero; low rates of genetic gain were also apparent in the national network of trials. Biomass, harvest index, and crop growth rate in the critical period had low rates of genetic change, and there were strong trade-offs between yield components and in their responses to selection. Breeding increased seed size at 0.5 % y⁻¹. Visual lodging scores decreased at 4.9 % y⁻¹. There was breakdown in resistance to Ascochyta blight, but it was restored in new varieties. Conclusions: Australian faba bean breeding contributed to on-farm yield and profitability through improved agronomic traits and seed quality. Low genetic gain in yield can be partially attributed to physiological trade-offs between traits, economic trade-offs between multiple breeding targets, and genotype-by-environment interaction. Implication: Under-researched crops require greater investment to match the genetic gain in yield of major crops.