SummaryChickpea (Cicer arietinum) is among the founder crops domesticated in the Fertile Crescent. One of two major forms of chickpea, the so-called kabuli type, has white flowers and light-colored seed coats, properties not known to exist in the wild progenitor. The origin of the kabuli form has been enigmatic.We genotyped a collection of wild and cultivated chickpea genotypes with 538 single nucleotide polymorphisms (SNPs) and examined patterns of molecular diversity relative to geographical sources and market types. In addition, we examined sequence and expression variation in candidate anthocyanin biosynthetic pathway genes.A reduction in genetic diversity and extensive genetic admixture distinguish cultivated chickpea from its wild progenitor species. Among germplasm, the kabuli form is polyphyletic. We identified a basic helix-loop-helix (bHLH) transcription factor at chickpea's B locus that conditions flower and seed colors, orthologous to Mendel's A gene of garden pea, whose loss of function is associated invariantly with the kabuli type of chickpea.From the polyphyletic distribution of the kabuli form in germplasm, an absence of nested variation within the bHLH gene and invariant association of loss of function of bHLH among the kabuli type, we conclude that the kabuli form arose multiple times during the phase of phenotypic diversification after initial domestication of cultivated chickpea.

Summary1. Based on expectations of the stress-gradient hypothesis for conspecific interactions, stress-sensitive genotypes may be able to persist in stressful environments when positive interactions between individuals occur under stressful environments. Additionally, we test how parental environmental effects alter responses to stress and outcomes of conspecific interactions in stress. While the stress-gradient hypothesis focuses on plant growth, earlier flowering may provide stress avoidance in short-lived organisms. 2. We studied responses to soil salinity and conspecific neighbour using genotypes of Medicago truncatula (Fabaceae) originating from saline or non-saline environments, utilizing seeds from parental plants grown in saline or non-saline environments. During the early stages of reproduction, we quantified leaf number, as a measure of vegetative growth, and number of flowers, as a measure of early reproduction potential. 3. Based on leaf counts, non-saline genotypes were better competitors than saline-origin genotypes and benefited from neighbouring plants in saline environments. This positive interaction was detected only when seeds were matured on parental plants grown in non-saline environments. Saline-origin genotypes displayed greater salinity tolerance in early flowering than non-saline genotypes. Plants with neighbours had greater early flowering, regardless of origin, consistent with facilitative interactions in stressful environments. 4. Transgenerational plastic responses influenced neighbouring plant interactions on plant growth, and results suggest that facilitative interactions may be transient only persisting for one generation. However, earlier flowering of non-saline genotypes when grown with a neighbouring plant is consistent with facilitative interactions resulting in reproductive benefits in saline environments, if earlier flowering is favoured in saline environments. 5. Synthesis. Adaptation to stressful environments allows tolerant genotypes to persist in these environments. Less appreciated is that stress-sensitive genotypes lacking such adaptations may persist in stressful environments via positive interactions with other individuals. Thus, positive interactions between individuals may explain the persistence of stress-sensitive genotypes within a population adapted to stressful environments.