GENETIC-ANALYSIS OF PARTIAL RESISTANCE TO BACTERIAL LEAF STREAK (XANTHOMONAS-CAMPESTRIS PV CEREALIS) IN WHEAT

Genetic variability of partial resistance to bacterial leaf streak was investigated in hexaploid winter wheat (Triticum aestivum.), using 16 parental genotypes and 48 pure lines (F10) derived from a composite c ross programme. Two experiments were undertaken in a controlled growth chamber. Seeds of all genotypes were grown under controlled condition s using a randomized block design with three replications. Each replic ation consisted of a row of 20 seedlings of each parent and pure line. An Iranian strain of bacterial leaf streak was used for the inoculati on of 12-day-old seedlings. In a third experiment, eight genotypes fro m parents and F10 pure lines representing a large variability for part ial resistance were inoculated with four other Iranian strains of bact erial leaf streak. A large genetic variability was observed amongst th e 64 genotypes for partial resistance to the disease. Partial resistan ce heritability estimates were rather high (70%), indicating that the resistance factors may be transmitted by crossing. Amongst all genotyp es investigated, 'DC2-30-N2' and 'IBPT-66' displayed the highest parti al resistance to the disease. Significant correlations between strains in the third experiment show that a genotype resistant or susceptible to one strain will have similar reactions with other strains. No sign ificant genetic gain was observed for partial resistance in the best p ure line of the 48 lines studied, when compared with the best parental line. Increasing the number of pure lines is likely to result in the identification of genotypes that might prove to be more resistant.