Assessment of groundnut (Arachis hypogaea L.) for genetic diversity using agro-morphological traits and SSR markers.

Abstract

Groundnut (Arachis hypogaea L.) offers one of the cheapest sources of proteins and economic empowerment to smallholder farmers in Africa, contributing significantly to world production and trade. Thus, improved groundnut seed with high quality attributes is needed. Therefore, pre-breeding activities involving agro-morphological attributes such as yield, disease tolerance/resistance, plant architecture among others are important in order to develop superior genotypes with the needed quality attributes. This study focused on assessing the performance and level of phenotypic variability and genetic diversity of groundnut genotypes using agronomic and morphological attributes, and simple sequence repeat (SSR) markers. Twenty-seven groundnut genotypes collected from International Crops Research Institute for the Semi-Arid Tropics (ICRISAT-Malawi) and Chitedze Agricultural Research Station (Malawi) showed highly significant differences in relation to number of branches, days to flowering, leaf color, seed yield and shelling percentage except for aflatoxin content and groundnut rosette disease. Moderate to high broad-sense heritability (0.56-0.71) was observed for number of branches, days to flowering and leafspot disease. The genotypes grouped into three main distinct clusters with those bred for low aflatoxin accumulation falling in the same cluster. Principal component analysis (PCA) had two PCs explaining 57.7% of the total variation with number of branches, flowering and aflatoxin contributing the most to the first PCA. Five genotypes; MP-68, ICGV-94379, ICGV-93305, CDI-1314 and CDI-0009 were identified as high yielding with low aflatoxin concentration hence are recommended for further pre-breeding activities such as increasing yield and resistance to diseases and aflatoxin. Using 20 SSR markers, 39 groundnut genotypes of diverse origin maintained at Agricultural Research Council – Grain Crops Institute in South Africa (ARC-GCI were assessed for genetic diversity. Results showed polymorphic information content (PIC) averaging 0.71, indicating the markers were very informative. A wide genotypic diversity with highest dissimilarity index of 6.4 between genotype pair RG562 and RG288, and smallest dissimilarity index of 0.9 between RG512 and RG562 was observed. Allelic diversity analysis showed high diversity among genotypes from southern Africa and southern America as indicated by the Shannon information index, mean number of observed alleles (Na) and mean number of effective alleles (Ne) which were relatively higher than in other groups. Analysis of molecular variation (AMOVA) results indicated that variation between and within individuals was more significant than between populations. Discrimination of the genotypes was not dependant on the geographical origin as genotypes belonging to different origins clustered in the same groups. Thus, genotypes with wide diversity can be used in breeding programmes as parents.