Biodiversity assessment of African locust bean (Parkia biglobosa) accessions from Savanna and Forest zones of Nigeria as revealed by seed storage proteins and RAPD markers

Abstract

Understanding the level and distribution of genetic diversity in African locust bean (Parkia biglobosa) would strengthen breeding and conservation programmes towards domestication and sustainable use of this species. Sixteen accessions of P. biglobosa were assessed for variability based on seed morphology, seed protein and DNA profiling. Significant variation in seed characteristics were observed across locations. Seed protein profiling by SDS-PAGE revealed homogeneity as most bands were found common in all accessions, indicating that the protein profiles are highly conserved. Protein profiling separated the 16 accessions into four major clusters at 0.93 similarity coefficient. Most accessions grouping into Cluster 1 had a similarity coefficient of close to 100% and were from the Derived Savanna suggesting the presence of duplicates. Accessions NH/2016/P14, NH/2016/P03 and NH/2016/P04 grouped into clusters II, III and IV; respectively. Sixteen RAPD markers generated a total of 256 bands of which 63.67% were polymorphic. Gene diversity ranged from 0.41 to 0.93 and Polymorphic Information Content (PIC) from 0.39 to 0.93. The RAPD-based dendrogram separated accessions into six groups at 0.68 similarity coefficient. Based on a polymorphic seed storage protein marker a genetically distinct accession NH/2016/P04 could be exploited for breeding purposes. The homogeneity of alleles and narrow genetic base as revealed by RAPD and SDS-PAGE analyses suggests possible loss of intraspecific genetic diversity. Thus, intensification of germplasm collections across the different agroecological zones and characterization using specific markers will give a better understanding of diversity of P. biglobosa in order to enhance selection towards conservation, breeding and sustainable utilization.