Ecophysiology and Phenology: Genetic Resources for Genetic/Genomic Improvement of Narrow-Leafed Lupin

Abstract

The narrow-leafed lupin (Lupinus angustifolius L.) is endemic to coarse-textured neutral to acid sands across the Mediterranean basin, distributed over temperature and rainfall gradients leading to increasing N–S terminal drought. L. angustifolius has a conservative reproductive strategy compared to other Old World species, with relatively early phenology, and a high proportion of physical dormancy in the seed. Nevertheless, appropriate phenology is the key adaptation to the terminal drought stress gradient across the species’ distribution, with flow on effects for water use, stress onset and productivity. Lupins have evolved early phenology in low-rainfall environments of the Mediterranean region, facilitating escape from the annual summer drought, where the opportunity cost of reduced fitness (yield potential) is partially mitigated by higher reproductive investment (harvest index). In high-rainfall environments, ecotypes are later, producing more biomass, leading to greater yield potential, associated with higher water use and earlier stress onset under water deficit. Domesticated lupins were selected for low or no vernalisation requirement in northern Europe and southern Australia, which mimicked the early, drought escape reproductive strategy of low-rainfall ecotypes, but may limit their yield potential in higher rainfall environments of Mediterranean-type environments. Breeding options for later flowering cultivars for long-season environments are constrained by the vernalization response: all late flowering cultivars (lanFTc1) are vernalization-sensitive types and are very late flowering in environments where the vernalisation requirement is not readily satisfied. The mutation efl provided a lower vernalization requirement, but produced unreliable yields. Potentially there are levers for delaying flowering time that may be revealed in phenological studies of wild L. angustifolius. We have discovered alternative alleles at the LanFTc1 locus that varyies in vernalisation-responsiveness, implying that there are other, more subtle phenology regulators to be uncovered in the species.