Abstract
• BRRI rice 87 and 72 appeared as moderately resistant to RLF infestation. • Cluster analysis grouped Kharif-II rice cultivars into 4 distinct clades. • Tannin and phenol (mg/g) were key precursors of resistance in rice. • Trichome density acted variably in providing physical protection against RLF. • PCA discovered 14 key variables out of 30 regarding total variance explained. In 2019 and 2020, ten rice ( Oryza sativa ) cultivars including check commonly grown in the Kharif-II season (June-November) were in-situ screened against rice leaf folder (RLF, Cnaphalocrocis medinalis ) in RLF-prone experimental plots in Bagerhat, Bangladesh, following RCBD (Randomized Complete Block Design) with three replicates and physicochemical analyses in the lab to evaluate their innate immunity to the pest. Of ten cultivars, only BRRI (Bangladesh Rice Research Institute) rice 72 and 87 tended to be moderately resistant (damage scale 3.00–4.99), while BRRI rice 73, 80, and 90 were susceptible to RLF (damage scale 7.00–8.99) and none appearing to be highly resistant or susceptible. In-field evaluation of Kharif-II rice cultivars against RLF, principal component analysis identified 14 key variables of 30 contributing maximum variance of PCA1 and PCA2. Cluster analysis grouped studied rice cultivars into four clades with clade II of BRRI rice 72 and 87 belonging to resistant club with high tannin and phenol contents (mg/g) assuring relatively higher yield (MT/ha) over others. A 3-D surface plot demonstrated, upsurge of larvae/ hill speeded up RLF incidence and severity (%) while bubble plot depicted, tiller infection (%) and RLF-fold length (cm) enhanced by leaf width (cm) limited the grain yield (MT/ha) in rice, well-supportive to correlation analysis. As per regression analysis, unit increment of tannin and phenol content (mg/g) declined tiller infection by 11 and 14%. Identified these two resistant cultivars could be used as potential parents in further breeding programs to develop an elite high yielding Kharif-II rice line by combining their novel resistance through hybridization.
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