Resistance to and extent of hyphal colonization and sporulation of my corellossiella cajani in pegeon pea lines

Abstract

Pigeonpea (Cajanus cqjan) in Kenya is attacked by Mycovellosiella leafspot, which is a highly devastating disease. Pathogenicity of Mycovellosiella cojani on susceptible pigeonpea was investigated under glasshouse conditions to provide proof for pathogenicity, which showed that the isolated fungus is pathogenic to pigeonpea. Fifty pigeonpea accessions planted at Kabete and Katumani were assessed for reaction to M. cajani The same accessions were also evaluated for resistance/ susceptibility to Mycovellosiella leafspot at seedling and flowering stage in the glasshouse. Rates of disease increase in infected leaves and defoliation varied among the pigeonpea accessions studied. The most susceptible accessions to M cajani were MKS TK 115, MKS KO 161/1, MKS KB 94/1 and MKS KO 252. Accessions KZ 56, ICEAP 00753, ICPL 93015, ICPL 86091, MKS KO 31 and KO 31 were resistant to Mycovellosiella leafspot disease. Resistant, ( KZ 56, ICPL 87109, ICEAP 00554), Intermediate (NPP 670, ICPL 93015, MKN KO 74) and susceptible (MKS KO 161/1, MKS KO 115, MKS KO 252) pigeonpea plants were inoculated in the glasshouse to study histological reactions. Within 3 hours from inoculation, spores of the fungus germinated in both susceptible and intermediate susceptible pigeonpea plants. Spores never germinated until 8 hours after inoculation in resistant varieties. Resistant varieties exhibited cell collapse in mesophyll cells directly below the penetration site and in surrounding tissue in 24 hours after inoculation and hyphae was limited to the epidermal cell penetrated first. Resistant varieties seemed to produce stomatal exudates that restricted fungal ingress. XIV Non gradular trichome seemed to block fungal penetration, both in resistant, intermediate resistant and susceptible genotypes.