Stage-specific resistance to leaf and neck blast ( Pyricularia oryzae ) in basmati and aromatic rice germplasm: phenotypic and multivariate analysis

Rice blast (Pyricularia oryzae) is a major constraint in basmati rice production. In the present study, 96 basmati and aromatic rice genotypes were evaluated for stage-specific resistance to leaf and neck blast under artificial inoculation (Ludhiana) and natural epiphytotic (Palampur) conditions in 2021 and 2022. Disease progression was assessed using incubation period, disease incidence, severity, and area under disease progress curve (AUDPC). Under artificial screening, 18 genotypes exhibited moderate resistance to leaf blast, while only six genotypes showed moderate resistance to neck blast. Genotypes IR 67,417-75–3-2–2-3, IR 72,860-62–1-1–3, Acharamati, Basmati C122, Pusa Basmati 1637, and Tetep consistently recorded lower AUDPC for both stages. In contrast, Pusa Basmati 1401 and Pusa Basmati 1121 were highly susceptible. Comparative AUDPC analysis indicated greater disease progression in neck blast than leaf blast. Two-way ANOVA revealed significant effects of genotype and year, whereas genotype × year interaction was non-significant, indicating stable genotypic response across years. Correlation analysis showed significant positive associations among disease parameters, while incubation period exhibited negative correlations. Heatmap-based clustering distinctly differentiated resistant and susceptible genotypes. Under natural epiphytotics, 13 genotypes showed resistance to leaf blast, whereas no genotype was resistant to neck blast, indicating limited availability of stable blast resistance within basmati and aromatic germplasm.