Virulence spectrum of populations of Pyricularia oryzae in irrigated rice ecosystems in Kenya

Pyricularia oryzae is a common pathogen in rice fields causing significant yield loss in Kenya. The virulence spectrum of the populations of P. oryzae in irrigated ecosystems in Kenya is not fully understood. Fifty-one rice lines carrying single resistance genes, recurrent parents and 3 local varieties were field-evaluated at Mwea, West Kano and Gamba to characterize virulence spectrum of populations of P. oryzae . West Kano, Mwea and Gamba had 68.63 %, 49.02 % and 40.2 %, respectively of the lines showing susceptibility to the populations of P. oryzae . The virulence spectrum of the populations of P. oryzae varied significantly suggesting the existence of a high pathogenic variability at the three locations. Lines with Piz-t , Pik-s , Pik-p , Pik-h , Piz-5 , Piz , Pit , Pish , Pi1 , Pi5 ( t ), Pi12 ( t ), Pik-m , Pita-2 , Pib and Pik were resistant to the population of P. oryzae at various locations. A local variety, BW196 was resistant to the populations of P. oryzae across the locations. Some lines carrying the same resistance genes showed different reaction to the populations of P. oryzae , suggesting existence of additional genes. Variation in resistance reaction was observed for some rice lines carrying the same genes in the CO39 and Lijiangxintuanheigu ( LTH ) genetic backgrounds. Most promising resistance genes observed in this study would be introgressed into preferred yet susceptible rice varieties in Kenya. Resistance gene(s) in BW196 should be identified for inclusion in breeding programs.