The lack of wheat cultivars resistant to spot blotch disease caused by hemibiotroph pathogen Bipolaris sorokiniana has become of increasing concern in our country. Twenty Egyptian spring wheat cultivars were field screened for spot blotch resistance associated with biotroph disease resistance genes that confer phenotypes LTN1 (Lr34), LTN2 (Lr46) and PBC (Sr2). Out of 14 cultivars recorded with phenotypes, resistance to spot blotch was associated with phenotype LTN in ten cultivars. Otherwise, susceptibility was associated with PBC in four cultivars. Genotypic alleles indicated that high levels of resistance were associated with the presence of both genes Lr34 and Lr46 in Sids-13, followed by the presence of Lr34 alone in Sakha-94, while low to moderate levels of resistance were recorded with Lr46 alone in nine cultivars, Giza-168, Giza-171, Gemmeiza-9, Gemmeiza-10, Gemmeiza-11, Sids-14, Sandweel-1, Beniswef-1, and Beniswef-4. Discouraging observation was recorded with Sr2 in three susceptible cultivars, Giza-168, Misr-1 and Misr-2. Morphological markers linked to biotroph disease resistance genes could be used to facilitate selection for spot blotch resistance. Genes Lr34 and Lr46 should be incorporated in breeding program for spot blotch resistance. Further studies on spot blotch resistance loci are in demand to provide more enough protection against the pathogen.
