EVALUATION OF BARLEY GENOTYPES FOR RESISTANCE TO NET BLOTCH AND DETERMINATION OF PATHOGEN DIVERSITY

Abstract

Net blotch caused by Pyrenophora teres is one of the most destructive foliar diseases of barley (Hordeum vulgare) in the world, Kenya included. Frequent evolution of net blotch pathotypes, continuous overcoming of resistance and changes in environmental factors require screening of advanced barley genotypes to identify more sources of host resistance and different strains of the pathogen for crop improvement. Twenty advanced barley genotypes from Moi University-East Africa Malting Limited collaborative project (2 susceptible, 2 resistant checks and sixteen with various attributes) were screened to evaluate their reaction to net blotch in the field (Purko sheep ranch in Mau Narok and Chepkoilel) and screenhouse (Chepkoilel). Disease assessment was done on a scale of 0-9. Net blotch infected leaves were collected and the fungus isolated to assess both morphological and physiological diversity. Data collected from the field and screenhouse were subjected to analysis of variance computed on Genstat version 12.2. Genotypes Cerise Laurel recorded the least level of disease severity while the susceptible checks gave the highest disease severity. Other groups of genotypes (HKBL, Six row and Syngenta) gave moderate resistant and moderate susceptible responses respectively. On the other hand, six row barley genotypes (54CAN, 77Aloe, Gloria Bar, NBD Petunia) had the highest ear infection. Five morphologically diverse P.teres groups were identified. The grouping of isolates was based on colony colours, texture and conidia characteristics. The different barley genotypes gave different responses to the five groups of isolates indicating that the genotypes had different levels of resistance. Approximately 5 isolates were identified indicating that different strains of the pathogen exist in the growing areas and that the virulence of P. teres is influenced by these strains. There is therefore need to confirm the molecular basis of the observed responses of the genotypes and the five morphological groups.