Morpho-molecular and nutritional profiling for yield improvement and value addition of indigenous aromatic Joha rice of Assam.

Short-grain aromatic Joha rice of Assam is a unique class of specialty rice having tremendous potential in domestic and international markets. The poor yielding ability of Assam's Joha rice demands its systematic characterization for an effective breeding program. This study investigates the morphological, molecular and biochemical profiles of twenty popular Joha (aromatic) rice cultivars indigenous to Assam. Distinctiveness, Uniformity and Stability (DUS) characterization of the cultivars revealed polymorphism in thirty-seven traits, establishing distinctiveness for their utilization in breeding programs. Unweighted Neighbor Joining (UNJ) clustering based on usual Euclidean distances for the polymorphic morphological markers grouped the cultivars into three clusters with eight, eleven, and one genotypes. The Joha rice cultivars showed significant differences for all the quantitative traits except for panicle length. The genotypic and phenotypic coefficients of variability (GCV & PCV) were high for grain yield ha-1 (24.62 & 24.85%) and filled grains panicle-1 (23.69 & 25.02%). Mahalanobis D2 analysis revealed three multi-genotypic and four mono-genotypic clusters of the cultivars. The first five principal components explain 85.87% of the variation among the cultivars for the traits under study; filled grain panicle-1 (0.91) and stem thickness (0.55) positively contributed to the first PC. The cultivars' average polyunsaturated fatty acids were 37.9% oleic acid, 39.22% linoleic acid, and 0.5% linolenic acid. Kon Joha 4 and Ronga Joha contained the highest iron (82.88 mg kg-1) and zinc (47.39 mg kg-1), respectively. Kalijeera, Kunkuni Joha, Kon Joha-5, Manimuni Joha and Kon Joha-2 accorded a strong aroma. PCR amplified 174 alleles with a mean value 2.64 across the 66 polymorphic SSR markers. PIC values ranged from 0.091 to 0.698, with an average of 0.326. The highly informative (PIC > 0.50) markers were RM316, RM283, RM585, RM1388, RM3562, RM171, R1M30, RM118, RM11and RM29 for identification of the twenty aromatic rice cultivars. PCR amplification of 27 SSR markers identified 28 unique alleles (97-362 bp) in 13 Joha rice cultivars, which can help their identification/DNA fingerprinting. The UNJ clustering based on Jaccard's coefficients classified the cultivars into three distinct clusters with eight, ten, and two genotypes. Our study revealed the nutritional richness of these specialty Joha rice cultivars and sufficient scope for yield enhancement through their interbreeding to keep quality intact.

Mutation induction in aromatic Joha rice of Assam for improvement of morpho-agronomic traits through M1 to M3 generation.

PURPOSE: The popular Joha rice cultivar Kon Joha, cultivated throughout the state, was used to induce mutations. Kon Joha is short-grain aromatic rice with excellent cooking quality. The cultivar is tall and late maturing with an average yield of less than 2 tons ha-1 and is susceptible to lodging. MATERIALS AND METHODS: The investigation through M1 to M3 generation aimed at improving the morpho-agronomic traits of the popular Joha rice cultivar Kon Joha. The experiments were carried out during the Sali season (winter rice) from 2017 to 2019 at Instruction-cum-Research (ICR) Farm of Assam Agricultural University, Jorhat (Assam). Dry uniform seeds of Kon Joha were subject to irradiation with 100-400 Gy of gamma rays from a 60Co source. The M1 generation used a randomized complete block design with four replications during Sali 2017. A total of 5998 M1 plant progenies were subject to screening in the M2 during Sali 2018. The M3 included 662 morpho-agronomic variants raised in the plant rows during Sali 2019, and 66 mutants were confirmed. RESULTS: The M1 of Kon Joha registered a reduction in germination, seedling height, pollen/spikelet fertility and plant survival at 400 Gy. All the traits showed highly significant differences among the doses in the M2 generation. The shift in trait means was in both directions as influenced by the genotype and mutagen dose. The 66 mutants exhibited significant differences for all traits in the M3 generation. Fifty mutants were shorter than the parent Kon Joha. The GCV and PCV estimates were high (>20%) for grain yield, biological yield, productive tillers, filled grains, and average panicle weight. All the traits except panicle length exhibited high heritability coupled with high genetic advance, suggesting the predominance of additive gene action and the effectiveness of simple selection. Grain yield showed a significant positive correlation with plant height, panicle length, filled grains, spikelet fertility, the average panicle weight and harvest index in the mutant population. CONCLUSIONS: Thus, mutation induction in Kon Joha proved useful in inducing desirable changes in plant architectural traits. The study further emphasized the short stature high yielding mutants with strong aroma for wide-scale testing in the state.