Genetic improvement of aromatic rice landraces through in vitro mutagenesis
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Date
2022-05-17
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Department of Plant Breeding and Genetics, OUAT, Bhubaneswar
Abstract
Aromatic rice is a special group of rice with pleasant aroma and excellent taste. They have a consumer preference and generally fetch high price in domestic and international market. Around 18% of non basmati rice exported is traditional aromatic rice (USDA, 2020). There is steady increase in demand for milled quality rice from India in the international market as Indian aromatic rice varieties are best suitable for traditional dishes.
There are a number of short and medium grain aromatic rice which includes aus type aromatic rice which is known as indigenous aromatic rice grown in India. The indigenous aromatic rice are characterized by tall plant stature, photoperiod sensitivity, susceptible to lodging and low yield. They possess unique genes tolerant to environmental stresses and high adaptability to low input conditions.
In vitro mutagenesis using ethyl methane sulphonate (EMS) is being used in plant molecular biology as a tool to identify and isolate genes and to study their structure, function more precisely and utilize for crop improvement. Genetic improvement of crop plants through conventional breeding program can be made more effective if coupled with the current in vitro cell culture techniques of cellular and molecular biology. The present investigation was undertaken with 40 aromatic rice genotypes involving diversity study for selecting genotypes for in vitro culture, identifying responsive genotypes for in vitro mutagenesis using 0.2% EMS, macro mutants study, finding effectiveness and efficiency of the mutagen dose under different treatments in M2 generation, field observation and evaluation of M3 and M4 generations for identification of desirable mutant lines.
High and moderate to high GCV, heritability and genetic advance was found in the characters like thousand grain weight, number of grains per panicle, effective tillers per plant, plant height, kernel length breadth ratio and single plant yield. 1000-grain weight, number of grains per panicle, kernel length breadth ratio, number of effective tillers per plant are found to be positively correlated while plant height, panicle length were found negatively correlated with yield, which have been used as criteria while selecting genotypes for genetic improvement of grain yield in indigenous aromatic rice.
Both callus induction and shoot regeneration were found to be genotype dependent having specific media requirement for efficient callus induction and shoot regeneration. Murashige and Skoog (MS) medium with 2.0 mg/l 2,4-Dichlorophenoxyacetic acid (2,4-D) was most suitable for callus induction and half MS medium with 2.0 mg/l 6-Benzyl amino purine (BAP) gave more shoot regenerations in local aromatic rice genotypes. Genotype Basumati and Kalikati were found to be more responsive to mutagenesis by EMS than Gangabali and Karpurajeera. EMS (0.2%) at 4 hours treatment was found to be most effective. Higher mutation rate was recorded in the genotypes which showed diplontic selection (Basumati and Kalikati). Appreciable genotypic variation in the mutant population existed and 32 mutant lines with desirable traits were identified in the M3 generation by multireplicated trial and estimates of skewness and kurtosis. Eleven competitive mutant lines, showing higher grain yield in the replicated yield trial, having positive skewness and negative Kurtosis values were identified and selected in M4 generation to be utilized further to advance generations through selection to develop superior varieties.