Biochemical and molecular characterisation of njavara types of rice (Oryza sativa L.)

Abstract

Characterisation and evaluation of Njavara types of rice (Oryza sativa L.) was under taken in the Department of Plant Breeding and Genetics and Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara during 2001 - 2005 with the aim to characterise the Njavara genotypes based on morphological, biochemical and molecular characteristics, to evaluate its nutritional qualities and to analyse the stability of quantitative and nutritional traits.

Morphological characterisation indicated that seven Njavara genotypes included in the present study exhibited similarity among themselves and with check variety for most of the qualitative characters. Some variations were observed with panicle type, panicle axis, apiculus colour, lemma and palea colour, seed coat colour and presence of awn. The Njavara genotypes viz., N1 and N2 (both Njavara types from Chittoor, Palakad) and N6 (Njavara type from Alwaye, Ernakulam) showed lemma and palea colour of black patches or furrows on straw background with black coloured apiculus, N3 and N4 (both Njavara types from Telllicherry, Kannur) showed lemma and palea colour of brown furrows on straw background with brown coloured apiculus, while N5 (Njavara type from Kottakkal, Malappuram) and N7 (Njavara type from Thrissur) showed a lemma and palea colour of gold furrows on straw background with an apiculus colour of straw. Njavara genotypes showed lesser days to maturity (67.9 to 79.1 days) with an average grain yield for Njavara genotypes ranging between 945.56 kg ha-1 and 2127.14 kg ha-1 was low compared to that of check varieties (2491.73 kg ha-1).

Majority of the Njavara genotypes expressed high protein content than check varieties. The geotypes N2 and N6 were recommended to be included in weaning and invalid foods and diets during pregnancy and lactation. The genotypes N1, N2, N6 and N7 appeared to have better nutritive value based on the content of free amino acids. Most of the Njavara genotypes had intermediate amylose content ensuring consumer acceptance. Among the Njavara genotypes N3 has highest soluble carbohydrate content while others showed medium soluble carbohydrate content and are desirable as component of weaning and invalid food due to reduced gelatinization period and easy digestibility.

Variability studies indicated that grain yield, straw yield and amylase activity provided a good genetic base for selection. The Njavara genotypes showed high heritability with high genetic gain for quantitative and nutritional characters. Correlation studies revealed that grain yield showed high positive correlation with high leaf width, days to 50 per cent heading, panicle length, days to maturity, straw yield, 1000 grain weight, grain width and amylose content. Nutritive factors like protein content and soluble carbohydrate content showed significant negative genotypic correlation with grain yield.

Genotype x environment interaction showed that, N1 was stable for plant height panicle length, straw yield and protein content where as N2 was stable for traits like days to 50 per cent heading, culm diameter, days to maturity, grain yield, grain width and amylose content. N3 was stable for leaf length, days to 50 per cent heading and amylase activity where as N4 for leaf length and leaf width. The performance of N5 was stable for seedling height, plant height, panicle length, days to maturity, grain length and width, protein content, free amino acid content and amylose content while N6 was stable for ligule length, culm number, grain yield, 1000 grain weight, soluble carbohydrate content, free amino acid content and amylase activity. N7 had recorded stable performance for 1000 grain weight and soluble carbohydrate content.

Biochemical characterisation indicated the possibility of utilising alcohol dehydrogenase polymorphism for identifying Njavara as a cultivar and also for identification of Njavara genotypes N1, N6 and N7. RAPD analysis of Njavara genotypes revealed good amplification with polymorphism for primers OPE 4, 6 and 16, OPP 7, 11, 12 and 19 and amplification with primers OPE 6, OPP 6 and OPP 11 exhibited unique bands for Njavara genotypes. The dendrogram drawn with two molecular markers viz., isozyme and RAPD revealed that the Njavara genotypes were grouped in one cluster whereas check varieties in another.