Screening of Brassica Spp. Genotypes against Sclerotinia Stem Rot under Natural Epiphytotic Conditions

Sclerotinia stem rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a major fungal disease affecting mustard (Brassica spp.), leading to significant yield losses, especially under cool and humid conditions. The present investigation was conducted during the Rabi 2024-25 at the Zonal Agricultural Research Station, Morena, RVSKVV, Gwalior, Madhya Pradesh, India, to evaluate seventy-three mustard genotypes for putative resistant to Sclerotinia stem rot under natural epiphytotic conditions. The experiment was laid out in a Randomized Block Design with two replications, and disease severity was assessed at 60 days after sowing employing a 0–4 lesion length-based disease rating scale. Significant genetic variability was observed among the genotypes for disease reaction. Out of the 73 genotypes screened, 51 (approximately 70%) were found to be completely resistant (rating 0), displayed no visible disease symptoms. Nineteen genotypes were found moderately tolerant (rating 1), with lesion lengths ranging between 0.1 to 2.0 cm. Two genotypes exhibited moderate susceptibility (rating 2), while none was categorized as susceptible (rating 3). Only one genotype namely GSC-6 was found to be highly susceptible (rating 4), displaying lesions greater than 6.0 cm in length. The results underscore the availability of diverse resistance sources within the mustard germplasm and highlighted the potential of resistant and moderately tolerant genotypes for further use in breeding programmes aimed to breed Sclerotinia-resistant cultivar (s). The study confirms the effectiveness of field-based screening under natural disease pressure and supports the integration of host plant resistance as a core strategy in sustainable disease management. The identified resistant genotype (s) hold promises for future genetic improvement and development of high-yielding, Sclerotinia stem rot -resilient mustard varieties.