Abstract

Javan Omondi Were and Julius Onyango Ochuodho

Colletotrichum species are among the destructive fungal pathogens of sorghum in Lake in Kenya. It is not clear whether all pathogenic species and sub-species infecting the three plant parts differ in their virulence and pathogenicity. Previous studies indicated that phosphorous efficient and Striga resistant genotypes were resistant to anthracnose while those resistant and/or susceptible to drought, aluminium toxicity and midge insect pest had mixed reactions. Sixteen genetically stable genotypes and four checks were randomized as sub-plots in plastic tubes in a split-plot arrangement under completely randomized design replicated twice in screenhouse. Morphologically identified leaf, stem and panicle isolates were randomized as whole plots. Inter-simple sequence repeat (ISSR) primer was used in genetic diversity assessment between Striga and phosphorous groups. Virulence and pathogenicity data were analyzed on Genstat version 12.2 while genetic diversity was assessed on NTSYS-pc version 2.1. Striga resistant and P-use-efficient genotypes were resistant to all isolates while the aluminium, drought and midge groups had mixed responses. Striga and P-use-efficient genotypes were genetically similar but differed from Striga susceptible and P-use-inefficient genotypes. Leaf isolates were less virulent than stem and panicle. Therefore, the level of virulence and pathogenicity of Colletotrichum species is influenced by hosts and pathogens genetic make-up.