Screening and field evaluation of wheat genotypes and integrated disease management strategies against spot blotch (Bipolaris sorokiniana)

Wheat (Triticum aestivum L.) stands as a staple food crop globally, yet its productivity is frequently compromised by various biotic stresses, particularly spot blotch caused by Bipolaris sorokiniana (Sacc.) Shoem. This study was conducted at Dev Bhoomi Uttarakhand University during the Rabi season of 2024-25 with the primary aim of evaluating wheat genotypes for resistance and assessing integrated disease management strategies against spot blotch under field conditions. Twenty wheat genotypes were screened under natural epiphytotic conditions. Disease resistance was measured using disease appearance date, a double-digit scoring scale, and Percent Disease Intensity (PDI). Genotypes G3, G7, and G16 showed delayed disease onset (up to 47 days), the lowest PDI values (20.53-25.53%), and strong resistance potential, while G6, G15, and G2 exhibited early infection and high susceptibility. For management trials, nine treatments incorporating bioagents, botanicals, bio-enhancers, and fungicides were evaluated using a Randomized Block Design (RBD) with three replications. The combination of Pseudomonas fluorescens seed treatment with two foliar sprays of Nativo (T6) resulted in the most significant disease control, with PDI reduced to 8.5% and Percent Disease Control (PDC) reaching 72.45% after the second spray. Treatments T7 (Trichoderma viride + hexaconazole) and T8 (Jeevamrit + hexaconazole) also showed high efficacy, with PDC values of 69.85% and 63.55%, respectively. Significant improvements were recorded in growth and yield parameters under effective treatments. T6 produced the highest mean number of tillers (21.4), productive tillers (17.8), and a test weight of 42.3g. The grain yield in this treatment reached 1.52 kg/plot, equating to 38.58 q/ha, marking a 23.93% increase over the untreated control. This study confirms that integrated disease management using bioagents, botanicals, and selective fungicides offers a sustainable and effective strategy for managing spot blotch in wheat. The results provide actionable insights for breeding programs and recommendable practices for farmers in disease-prone areas.