Genetic diversity analysis of specialty glutinous and low-amylose rice (Oryza sativa L.) landraces of Assam based on Wx locus and microsatellite diversity

ABSTRACT

The sticky rice of Assam is traditionally classified as bora (glutinous) and chokuwa (semi-glutinous) basedon their stickiness after cooking. The Waxy (Wx) gene encodes for granule-bound starch synthase (GBSS)that controls the synthesis of amylose, which is a key determinant of rice end-use quality attributes. In thisreport, we analysed the level of variation in grain quality traits in a collection of bora and chokuwacultivars, and examined the nucleotide diversity at the Wx locus of selected rice accessions to identify thepossible cause of low-amylose in these rice cultivar groups. The Wx gene sequencing from 24 bora andchokuwa cultivars revealed several nucleotide variations that can explain the variation in the amylosephenotypes. The nucleotide polymorphisms in the downstream intron regions were similar to those reportedin Bangladeshi Beruin cultivars. Among the Wx polymorphisms, the CTn microsatellite in exon 1 and G/TSNP in intron 1 (G/T-Int1) should be considered for marker assisted breeding involving bora cultivars. TheWx gene tree, classified the bora accessions possessing the G/T-Int1 SNP as japonicas. However, clusteranalysis using microsatellite markers classified the bora and chokuwa cultivars as indica, and intermediateof indica-aus. The findings of this study supplemented our understanding on the evolution of the Wx geneunder human selection. The results will assist plant breeders to effectively improve the bora and chokuwalandraces.