EVALUATION OF PIGEONPEA (Cajanus cajan (L.) Millsp) GENOTYPES FOR YIELD PERFORMANCE, GENETIC DIVERSITY AND RESISTANCE TO INSECT PEST COMPLEX IN NORTH RIFT VALLEY- KENYA

Abstract

Pigeonpea (Cajanus cajan (L.) is largely considered as an orphan crop and remains one of the most drought-tolerant legumes. However, insect pest complex pod borer (Helicoverpa armigera), Sucking bug (Clavigralla tomentosicollis) and pod fly (Melanogromyza cholcosoma) is the major limiting factor to its production by causing tremendous loss ranging between 16-18% for pod borer, 69%-73% for sucking bug and 9-15% for pod fly in Kiboko and Kabete but no reported statistics in North Rift valley Kenya. The objective of this study was to evaluate yield performance, genetic diversity and level of resistance to insect pest complex among sixteen selected Pigeonpea genotypes. The study was carried out in three varied sites at (KALRO- Marigat, Fluorspar and ATC Koibatek) during the long rain season of April-November 2014. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications in 75x25 cm inter and intra spacing. The results revealed six genotypes (ICEAPs 01147, 1147-1, 01159, 00911, 0979-1, and 1154-2) with a yield of more than 1.0 t/ha across the three sites. Grain yield was positively significantly correlated with height at maturity, secondary branches, pods /plant, seeds /pod and 100 seed weight. However days to 50% flowering was negatively correlated to yield. The seed damage by pod borer was 1.9%, 3.6% and 37.2% in Koibatek, Fluorspar and Marigat respectively. However Pod fly caused a damage of 5.9% in Marigat, 5.9% in Koibatek and 6.8% in Fluorspar while Seed damage by sucking bug was 39.3% in Marigat, 8.4% in Koibatek and 2.9% in Fluorspar. Genotypes ICEAPs 00902, 01541 and 1154-2 were tolerant to the insect pest complex at both podding and seed level. Grain yield associated negatively (P≤0.05) with pod borer eggs, pod borer pod damage, seed damage by sucking bug and pod borer. The molecular cluster analysis based on neighbor joining grouped the genotypes into three distinct clusters based on resistant/ susceptible levels. The markers generated 78 alleles in total with a mean of 3.67 alleles per locus. However, Polymorphism information content ranged from 0.13 to 0.70 with Marker CcM1348 being highly polymorphic and informative by providing 70% genetic diversity information. Therefore, there is need for further testing of the high yielding varieties identified in this study for other important agronomic traits in two seasons. Also mechanisms of resistance to this insect pest complex need to be identified and molecular markers to be developed using Single Nucleotide Polymorphism (SNP) markers through Genome Wide Association Studies (GWAS).