Linking phenology, harvest index and genetics to improve chickpea grain yield.

Understanding phenology and its regulation is central for the agronomic adaptation of chickpea. We grew 24 chickpea genotypes in 12 environments to analyse: the environmental and genotypic drivers of phenology; associations between phenology and yield; and phenotypes associated with allelic variants of three flowering related candidate loci: CaELF3a; a cluster of three FT genes on chromosome 3; and an orthologue of the floral promoter GIGANTEA on chromosome 4. A simple model with 3 genotype-specific parameters explained the differences in flowering response to daylength. Environmental factors causing flower abortion, such as low temperature and radiation and high humidity, led to a longer flowering-to-podding interval. Late podding associated with poor partition to grain, limiting yield in favourable environments. Sonali, carrying the early allele of Caelf3a (elf3a), was generally the earliest to set pod, had low biomass but the highest harvest index. Genotypes combining the early variants of GIGANTEA and FT orthologues featured early reproduction and high harvest index, returning high yield in favourable environments. Our results emphasise the importance of pod set, rather than flowering, as a target for breeding, agronomic, and modelling applications.