Studies on Grain Quality Characters and Related Gene Expression Analysis in Aromatic Rice (Oryza Sativa L.)

Abstract

Rice (Oryza sativa L.) is most vital cereal crop which is a good source of energy for half of the world population. Rice is consumed as whole milled grain so is characterized by milled grain appearance and grain endosperm properties. 29 aromatic and 1 non-aromatic rice genotypes were chose for grain quality studies. The results of the morphological and bio-chemical analysis revealed that mostly aromatic Basmati genotypes had high thousand grain weight, extra-long slender grain appearance, high grain elongation ratio, stron aroma, intermediate amylose content, intermediate to high alkali spreading value and hard to medium gel consistency. Gene expression analysis showed the expression level of certain genes related to grain quality depends on genotypes. Aromatic Basmati genotypes had low expression level of GS3 gene but high expression level of GBSSI gene and Waxy gene which are generally long grain, hard and become fluffy on cooling. Aromatic non-Basmati genotypes had short to medium grain appearance, less elongation ratio, less kernel length before and after cooking, strong aroma, low amylose content, intermediate to high alkali spreading value and soft gel consistency. Gene expression analysis revealed aromatic non- Basmati genotype had high expression level of GS3 gene but low expression level of GBSSI gene and Waxy gene which are generally short to medium grain, sticky and tender on cooking. We performed a comparative In-silico study of certain genes related to rice grain quality characters. Nucleotide sequences analysis revealed that aromatic Badh2 gene had 8bp sequence deletion in exon 7 that produce a truncated amino acid while non-aromatic Badh2 gene did not. Similarly, Nucleotide sequence analysis of GBSSI gene showed high similarity with identities 0.92 and non-aromatic genotype consists of 1841 nucleotide encodes 605 aa and aromatic Basmati genotypes consists of 1947 nucleotides encodes 609 amino acid. GS3 gene for long form grain had nucleotide deletion in exon 2 that caused a truncation amino acids whereas GS3 gene for short form grain did not had nucleotide deletion.