Assessment of marker genotypes associated with the resistant genes in a set of rice cultivars for brown planthopper, blast disease, and bacterial leaf blight

Abstract

Brown planthopper, bacterial leaf blight and rice blast disease are identified as devastating stresses of rice cultivation. Developing host plant resistance is considered an effective and environmentally friendly management strategy. In Sri Lanka, limited studies have been carried out to assess the genetic basis of disease resistance. Bph3, Pikh and Xa21 genes convey significant resistance against biotic stresses. The current study was conducted to identify whether markers linked to Bph3, Pikh and Xa21 genes can facilitate the identification of resistant varieties. A total of 34 varieties were selected for the study and their morphometric and marker allelic data were subjected to descriptive and statistical analyses. Moderate height varieties depicted high yield. Most of the varieties showed significant moderate resistance against stresses. Molecular marker analysis yielded polymorphic banding patterns for all markers. RM 589 marker linked to Bph3 dominant gene provides overlapping banding patterns for the cultivars with different resistance levels making it impossible to discriminate resistant and susceptible cultivars. RM 206 marker linked to gene pikh provided the expected PCR product size for RM 206 marker is 147 bp. The resistant varieties gave band lengths of 140 bp, 170 bp and susceptible or moderately susceptible varieties produced band lengths of 160 bp and 155 bp. pTA 248 marker linked to Xa21 locus produced bands length of 670 bp, 740 bp and 930 bp. The 930 bp band was observed only in IRBB 60 variety. IRBB60 amplified 930 bp fragment confirms the possession of the resistant allele of Xa21 in its background. Presence of 730 bp indicates the susceptible allele. None of the Sri Lankan varieties carries a resistant allele for Xa21 as they have 730 bp allele for pTA 248. The rice varieties such as Bg251, Bg455, Bg450, Bg305, At402, At308 and At354 contain high yielding traits but need to improve for the pest and disease resistance.