Evaluation of Powdery Mildew Resistance in Northwest Himalayan Bread Wheat Landraces and Doubled Haploid Lines

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is an important disease of bread wheat in the cool, humid hill environments of Himachal Pradesh. This study evaluated powdery mildew development in 50 bread wheat genotypes comprising 16 doubled haploid (DH) lines, 29 north-west Himalayan landraces and five checks. The trial was conducted at Palampur during the 2021–2022 Rabi season under natural epiphytotic conditions using a randomised block design with three replications. Disease reactions were recorded on a 0–9 scale at five Zadoks growth stages (Z20, Z30, Z41, Z51 and Z69). Disease progression was assessed using the area under the disease progress curve (AUDPC) and relative AUDPC (rAUDPC). No genotype remained entirely free from powdery mildew. The mean disease score increased from 1.24 at Z20 to 6.16 at Z69. AUDPC values ranged from 100.5 in DH-114 to 313.0 in T-79, with a mean of 200.5 (95% confidence interval: 185.4–215.6). Nine genotypes recorded AUDPC values below 150, including four DH lines, three landraces and two checks. Mean AUDPC was higher in landraces (215.8) than in DH lines (180.5), although the reported comparison among germplasm categories was not statistically significant (Kruskal–Wallis P = 0.082). These findings identify genotypes with relatively slow disease progression under the tested conditions and support their further evaluation as potential sources of resistance to powdery mildew.