Phenotypic And Genetic Characterization Of Selected Kenyan Groundnut (Arachis Hypongaea.L) Varieties

ABSTRACT

Groundnuts also known as peanut (Arachis hypongaea L.) and ‘njugu karanga ’locally is one of the principle economic oilseed and is largely cultivated in warm regions of Kenya. Groundnut contributes significantly to domestic food security and cash revenue through the sale of the seeds. The study aimed at evaluating genetic diversity and phenotypic characterization of groundnut varieties grown in some parts of Kenya. Thirty genotypes each from six varieties (ICG83708, ICGV99568, CG7, ICGV12991, RV and Chalimbana) were obtained from KALRO (Kakamega) based on quality traits. Digital Vernier calipers was used to measure seed length and breadth while an electronic weighing balance measured seed weight in each variety with five replicates. Seeds were planted in cylindrical cans with 0.2m3 of soil and allowed to germinate for two weeks. Leaf trait measurement was done using 15cm ruler and the data was recorded in excel spreadsheet and exported to MINITAB v17 software. Extraction of genomic DNA from each genotype variety was done using a modified CTAB method. DNA amplification was carried out using11 SSR primers and the products resolved in 2% agarose gel with manual scoring of bands. GenALEx 6.502 software was used to calculate AMOVA and heterozygosis, PowerMarker version 3.25 was used to calculate genetic distance, PIC, Allele number, gene diversity while phylogeny reconstruction was done using DARWIN version 6 with Bootstrap values at 1000 permutations. A dendrogram of cluster analysis was constructed using UPGMA based on simple matching coefficient of 11 microsatellite markers. Clustering of genotypes based on Euclidian distance of the 7 seed and leaf traits were grouped into 2 major clusters .in terms of the principle components generated the first two showed more Eigen values with 67.2% variability of all the traits studied. On genetic diversity a total of 35 alleles were detected across the loci of 11 primers used. Major allele frequency ranged from 0.9333 in IPAHM 165 to the least frequency of 0.6333 in IPAHM 176 with an average of 0.7610 across all the markers. The expected heterozygosity had a mean of 0.3178 with highest value of 0.4511 in IPAHM 176. The lowest dissimilarity index was observed between replicates of icg83708 and icgv99568 while Chalimbana-4 had the highest dissimilarity index of 0.7826.Phylogenetic tree had three major clusters and with high bootstrap values in genotype icgv99568 replicates.cg7 replicates clustered together with high confidence limits of 70%.AMOVA on the genotypes studied had observed within population variations of 69% while 31% was attributed to among population variations. From the study results phenotypic diversity indicated variations based on seed and leaf traits. Primer IPAHM176 was the most informative marker and should be utilized in selection of parent plants with good quality traits. Breeding programs on groundnuts could utilize grain and seed traits since they are informative and discriminatory.