Karyotypic analyses of accessions of Kersting’s groundnut

Abstract

Kersting’s groundnut (Macrotyloma geocarpa) is an orphan crop of significant food and household income in sub-Saharan Africa. The objective of this study was to evaluate the chromosomal variability among the accessions of the species through analysis of the karyotypes. Six accessions of Kersting’s groundnut were subjected to conventional cytological techniques, using root tip meristems. The somatic chromosome number was 2n = 20 in all the accessions. The highest total chromosome length was obtained in Tkg 1 (1.739 + 0.047); while the least was in Tkg 12 (1.014 + 0.029). All the accessions had metacentric, submetacentric and subtelocentric chromosomes. However, there was a preponderance towards metacentric chromosomes, suggesting a symmetrical karyotype, which is known to be a primitive condition. Five of the accessions were grouped in karyotype 2A while one accession, Tkg 9 was grouped in karyotype 2B. The 2B karyotypes are known to have greater chromosomal asymmetry than 2A; thus Tkg 9 may be advancing evolutionarily faster than the other accessions. Hierarchical cluster analysis divided the accessions into three clusters. Cluster 1 comprised of four accessions (Tkg 1, Tkg 6, Tkg 9 and Tkg 11); while Cluster 2 comprised of one accession (Tkg 6); and cluster 3 had one accession (Tkg 12). Tkg 6 and Tkg 12 were observed to be distantly related to the other accessions; as such could serve as parents in hybridisation programmes to generate wider variability for the improvement of the species.