Genetic diversity assessment of Phaseolus vulgaris L. landraces in Nigeria’s mid-altitude agroecological zone

Abstract

Phaseolus vulgaris L. is a valuable and highly nutritious food legume. In Nigeria, it is highly underutilized, being consumed in few parts of Plateau and Taraba States within the mid-altitude agroecological zone. In order to provide information on breeding and improvement for better acceptability, genetic diversity among eleven landraces grown within this zone, belonging to six phenotypic classes based on seed colour, was assessed using random amplified polymorphic DNA (RAPD) and soduim dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of total seed proteins. RAPD-PCR amplified products ranged from 4 to 9 bands. Number of alleles observed and mean gene diversity within the different phenotypic classes ranged from 1.0 ± 0 to 1.63 ± 0.49 and from 0.13 ± 0.19 to 0.26 ± 0.21, respectively. The highest genetic distance was between white and canberry seeded varieties (81.09%) while the least was between red and pinto accessions (9.22%). However, the highest number of polymorphic loci (40), percentage polymorphism (63.49%), Nei’s gene diversity (0.26 ± 0.21) and number of alleles (1.63 ± 0.49) was found within pinto varieties. Nei’s genetic similarity between landraces from the two states was 91.72% indicating a profound founder effect which could be facilitated by high germplasm exchange between these states. Jaccards similarity coefficient between the landraces based on total seed proteins bands was 1.00. However, genetic relationships and clusters drawn from RAPD and SDS-PAGE data differed, with most of the landraces belonging to separate clusters in the dendrograms obtained from both methods. High polymorphism suggests a broad genetic base among the landraces. The study of more specific seed proteins such as phaseolin as biochemical markers might better elucidate diversity present within the landraces.