Karyotype analysis of two local varieties of Cajanus cajan in Hainan, China

Cajanus cajan is an important legume crop in the tropical and subtropical regions of China, acting as a multi-purpose plant that integrates grain, feed, and medicine. Additionally, as a pioneer plant, C. cajan contributes to soil and water conservation and soil improvement. Despite the long history of cultivation and the high resource diversity of C. cajan in Hainan, there has been limited research on its cytogenetics. In this study, C. cajan from two important C. cajan producing areas in Hainan, ‘Baoting’ and ‘Baisha’, were evaluated. Based on karyotype analysis, the following results were obtained: 1) for C. cajan obtained from ‘Baoting’, the karyotype formula was 2n = 2x = 22 = 16m + 6sm, the ninth group chromosome was observed to have a satellite, and the relative length composition was 2n =1L + 5M₂ + 3M₁ + 2s, typed 1A; 2) for C. cajan obtained from Baisha, the karyotype formula was 2n = 2x = 22 = 20m + 2sm, neither satellite nor B chromosome were observed, and the relative length composition was 2n = 1L + 4M₂ + 5M₁ + 1s, typed 2A. The chromosomal characteristics of the two C. cajan plants from Hainan provide insights into new techniques for C. cajan resource identification, as well as a reference for germplasm innovation and new variety breeding.