Characterization And Incorporation Of Fusarium Wilt Disease Resistance In African And Asian Pigeonpeas [Cajanus Cajan (L.) Millsp.] Germplasms

ABSTRACT

Fusarium wilt is a plant disease caused by Fusarium udum (Butler). It is a soil and seed borne fungus which causes significant yield losses in susceptible cultivars throughout the pigeonpea growing areas. Numerous control measures have been suggested to alleviate the problem but their success has still remained low due to prohibitive costs. Development of resistant pigeonpea varieties is sought as an alternative for control of the disease. However, the task of developing resistant pigeonpea varieties has been complicated by variability in the pathogen. To undertake the study, the whole task was divided into three sub studies: Variability and aggressiveness of Fusarium udum, genetic diversity, inheritances and SSR marker segregation for the disease resistance, combining ability in yield and yield components. The Variability and aggressiveness of Fusarium udum isolates against 21 pigeonpeas were examined using pathogenicity and morphological characterizations, high level of resistance was noted in ICEAP 00040, ICEAP 00540 and ICEAP 00557 genotypes hence could be used as new source of resistance thus further studies using molecular markers were recommended. Sixty genotypes and 16 primers were used in diversity analysis. Close relationship was observed between Indian and East African collections. This could be diversified through selection, recombination and introduction of new source of variability from genetically diverse pigeonpeas. The study of genetic inheritance revealed a 3:1 ratio in F2, thus proved a single dominant gene which could be used to donate genes for disease resistance into genotypes where Fusarium wilt is of an economic problem. The F2 populations with resistant and susceptible parents were characterized using six SSR markers. Only CZ681922, CZ681962 and CZ681928 showed high correlation to phenotypic expression, hence application of these markers was recommended for sorting resistant genotypes. Path analysis showed that number of pods per plant, seeds per pod and 100 seeds weight had good contribution to yield and could be used as selection criteria in breeding programs. With

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regard to combining ability parents, P2, P5 and P6 with crosses P1×P2, P1×P4, P1×P5, P2×P3, P2×P4, P3×P6 and P5×P6 were good general and specific combiners hence could be used by breeders as source of composite and hybrid materials.