Abstract
Tan spot is one of the most economically significant diseases of wheat (Triticum aestivum) in southeastern Kazakhstan, where infection levels can reach up to 70% in epiphytotic years due to the combined effects of favorable factors such as high humidity, crop residues, and monoculture. 60 wheat lines were evaluated for resistance under field conditions at the adult plant stage. Disease severity was assessed using Saari and Prescott’s (1975) scale modified by Kremeneva (2007), and disease dynamics were quantified using the AUDPC index (Wilcoxson et al., 1974). PCR amplification was performed following Faris et al. (2010) to identify Tsn1/tsn1 alleles. The genotypes exhibited substantial variability in plant height (80–126 cm) and NDVI (0.51–0.65), reflecting differences in physiological status and productivity. Field evaluation revealed clear differentiation: 33 accessions showed complete resistance (AUDPC = 0), whereas susceptible genotypes had AUDPC values ranging from 88 to 455. Molecular screening identified a high frequency (70%) of the recessive tsn1 allele associated with insensitivity to the PtrToxA toxin of PTR. Carriers of tsn1 showed lower disease severity and reduced AUDPC values, while genotypes carrying Tsn1 exhibited more pronounced disease development. Integration of molecular and field data demonstrated strong concordance and confirmed the reliability of the Xfcp623 marker. The practical significance lies in identifying promising resistance donors, including 25-ICARDA-IPBB-2013 × D.588 ma F7 Bermet × RWKLDN9, D.22-ICARDA-IPBB-2013, 1060 D.5353 [(CWARTN) Super KAUZ × D.1017 F7 (Yr15 × Yuzhnaya-12)], Morocco × Steklovidnaya 24, 1138 D.906 F5 (Almaly×29266)×D.5357 Pastor, and D.1055 (DIAMONDBIRD/GALLYA-ARAL1//TAM200/ KAUZ) × D.305 Roughrider, combining tsn1 allele with adaptability and productivity.