Insight to the genetic diversity of pigeon pea Cajanus cajan (L.) Millsp. and cowpea Vigna unguiculata (L.) Walp. germplasm cultivated in Nigeria based on rbcl gene region

Pigeon pea Cajanus cajan (L.) Millsp. and cowpea Vigna unguiculata (L.) Walp. are two of the important seed legumes of Africa and are relatively more drought-tolerant than many other legumes. Nigeria is the largest producer of cowpea in Africa, while pigeon pea is yet to be commercially cultivated in Nigeria. The genomic information on cowpea is known but not for pigeon pea, and this has hindered the development of superior varieties. Most importantly, although various genetic markers have been used in both legumes to elucidate their genetic diversity, simple sequence repeats and single nucleotide polymorphism markers are preferred for genetic and plant breeding applications. We investigated the genetic diversity in the two legumes and traced the evolutionary relationship of the large subunit of the ribulose-bisphosphate carboxylase/oxygenase (RuBisCo) (rbcl) gene in selected organisms using cowpea and pigeon pea rbcl gene sequences as queries. The genetic diversity study analysed 25 pigeon pea and 22 cowpea accessions using rbcl gene region primers. A total of 432 polymorphic sites were detected from the obtained legume DNA sequences. The phylogeny of the two legumes was a location/origin of adoption to the germplasm. Analysis of molecular variance of the rbcl gene showed that among-population variance was 0% and within-population variance was 100%, suggesting a wide genetic diversity among pigeon pea and cowpea populations. This study provided a basis for the understanding of the evolutionary relatedness and the genetic diversity of cowpea and pigeon pea accessions. To substantiate the diversity of these legumes, wider regional sampling of seeds in Nigeria should be implemented.

Automated summary

This study investigated the genetic diversity and evolutionary relationship of pigeon pea and cowpea. The results showed a wide genetic diversity among pigeon pea and cowpea populations. This study provides a basis for further understanding the diversity of these legumes.