Phenotypic variation in Australian wild Cajanus and their interspecific hybrids

Wild species are potential sources of genetic diversity for crop improvement. Variation in agronomically important traits has been reported in the wild Cajanus species however, the Australian wild species have not been characterized to date. A subset of four Australian wild Cajanus acutifolius (F.Muell.) Maesen accessions and 57 interspecific hybrids of C. acutifolius, Cajanus lanuginosus (S.T.Reynolds & Pedley) Maesen, Cajanus lanceolatus (W.Fitzg.) Maesen, and two C. cajan genotypes were investigated to assess the phenotypic diversity for 17 qualitative and six quantitative traits. Significant variation in stem thickness, days to 50% flowering (dff) (f.pr < 0.001), and raceme number (f.pr < 0.021) within a group, and plant height, stem thickness, leaf size and dff (f.pr < 0.001) between groups was found. In contrast to earlier reports, some wild C. acutifolius accessions were found to be early (AGG31815WCAJ with 117 days) and medium (AGG316925WCAJ with 140 days) maturating types. Positive correlation of plant height with stem thickness (r = 0.714), and dff (r = 0.780) was observed in late maturing types. Positive correlation of stem thickness with leaf size (r = 0.709), and dff (r = 0.760) were identified in all groups. Even though there was a slight negative correlation of the number of racemes with plant height (r = − 0.126) and stem thickness (r = − 0.190), a considerable positive correlation was observed with secondary (r = 0.536) and tertiary (r = 0.500) branches. The F1s produced with wild Cajanus acutifolius as the female parent were sterile demonstrating the potential for use in hybrid breeding programs.