GENETIC-ANALYSIS OF RESISTANCE TO BACTERIAL LEAF STREAK CAUSED BY XANTHOMONAS-CAMPESTRIS PV UNDULOSA IN BREAD WHEAT

The inheritance of resistance to bacterial leaf streak or black chaff of wheat was studied under field conditions, with an artificial epidem ic of Xanthomonas campestris pv. undulosa. A complete series of crosse s between five parents, differing in reaction to X. c. pv. undulosa, w as generated. Disease was recorded at two different stages of growth. No evidence of cytoplasmic effect was found from the comparison betwee n reciprocal F1 crosses. The study of the F3 generations attested that five genes were involved in resistance to bacterial leaf streak. Sepa rate analyses carried out for the two scoring dates were mutually cons istent: genotypes, number of genes, and their action and relative impo rtance were verified. The genes differed in strength of expression of resistance. One of the two strongest genes, Bls1, is present in all th ree superior parents, Pavon 76, Mochis T88 and Angostura F88. Resistan ce was not complete, and proved to be stable over the season.