How has narrow-leafed lupin changed in its 1st 40 years as an industrial, broad-acre crop? A G x E-based characterization of yield-related traits in Australian cultivars

Although the narrow-leafed lupin was 1st domesticated in Central Europe in the early 20th century, it remained a minor crop until further domestication in Western Australia (WA) in the 1950'1970s, and Australia has dominated world production since the mid-1980s. In order to investigate varietal adaptation and changes over time in Australian breeding, seed yield and a range of related traits were measured in multi-environment historical variety trials. Cultivar differences in most traits were well explained by vernalization response, accounting for 38'94% of the genotype main effect. Vernalization responsive (VR) cultivars were much more daylength responsive than vernalization unresponsive (VU) varieties, but much less responsive to ambient temperature, tending toward 0 as vernalization induction decreased. Phenology had a strong influence on yield and related traits, all of which were measured exclusively in WA, under warm Mediterranean climates with weak, variable vernalization induction. The early phenology VU cultivars were more yield-responsive to WA environments than VR types, and were characterized by rapid growth rates, high seed and biological yield, harvest index, fecundity, large seeds and a lower proportion of total biomass invested in the main stem.Cultivar productivity, yield responsiveness, harvest index and fecundity have increased over time in both vernalization response types, while flowering has become earlier. Seed yield increases are associated with increased main stem productivity, with higher seed numbers due to both increased pod set and seed numbers per pod over time. Lupin breeders have selected strongly for drought escape, an appropriate strategy for the strongly Mediterranean climate of the northern WA grainbelt, but which is likely to limit yield potential in longer season environments. Because ambient temperature and vernalization responses are confounded, and there is little variation within each cultivar pool, it is currently not possible to develop longer season cultivars for warm Mediterranean climates. To produce specifically adapted cultivars with phenology appropriate for short- and long-season environments, as is the case in widely adapted legumes such as chickpea or lentil, a broader range of temperature responses in VU backgrounds is required. This will require careful parental selection, based on an understanding of flowering responses to temperature, photoperiod and vernalization.