Genetic variability studies for qualitative and quantitative traits in some recently developed rice varieties of Bangladesh

Abstract

Background

The study aimed to assess six recently developed rice varieties: BRRI dhan84, BRRI dhan89, BRRI dhan92, BRRI dhan99, BRRI dhan100, and BRRI dhan102 of Bangladesh. The primary objectives were to assess genetic variability and key genetic parameters for selected qualitative and quantitative traits, identify, and prioritize promising traits for targeted improvement in rice breeding programs aimed at enhancing quality, productivity, and adaptability in Bangladesh's agriculture. The experiment was conducted using a completely randomized design with three replications. A total of 22 qualitative and quantitative traits were assessed across six varieties. Additionally, the study assessed genetic variability, genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), heritability (h²b), genetic advance (GA), and genetic advance as a percentage of the mean (GA%) across multiple traits.

Results

The ANOVA results indicated that the mean squares were very highly significant for most traits among the six rice varieties studied. Grains per panicle exhibited the highest genotypic and phenotypic variances, recorded at 579.88 and 742.85, respectively, while chlorophyll a at 45 days after transplanting showed the lowest values, both recorded at 0.05. Zinc content demonstrated the highest genotypic and phenotypic coefficients of variation (GCV and PCV), recorded at 37.13% and 37.95%, respectively, whereas carbohydrate content showed the lowest, with GCV and PCV values of 2.98% and 3.35%, respectively. Traits such as iron content with 99.84%, amylose content with 98.47%, protein content with 96.54%, zinc content with 95.73%, and thousand-grain weight with 94.29% exhibited minimal environmental influence due to their high heritability estimates (>60%). GA was highest for grains per panicle, with a value of 43.83, followed by filled grains per panicle with 29.15, and zinc content with 12.63. In contrast, the lowest GA was recorded for chlorophyll a at 70 days after transplanting, with a value of 0.29, followed by chlorophyll a at 45 days with 0.43, and chlorophyll b at 70 days with 0.68. High heritability along with high GA as a percentage of the mean (GA%) was observed for several key traits, including iron, protein, and zinc content; thousand-grain weight; chlorophyll a at 45 days after transplanting; total chlorophyll at 45 and 70 days after transplanting; grain, straw, and biological yield; number of grains and filled grains per panicle; and number of productive tillers per hill. These traits are likely governed by additive gene action, indicating strong potential for improvement through simple selection methods. In contrast, traits such as amylose content, harvest index, and panicle length exhibited high heritability with moderate GA%, suggesting the involvement of both additive and non-additive gene effects. Carbohydrate content showed high heritability but low GA%, implying a predominance of nonadditive gene action and the need for improvement through combination breeding strategies.

Conclusion

These findings highlight the genetic potential of newly developed rice varieties and provide valuable guidance for breeding programs aimed at enhancing yield, nutritional quality, and adaptability in rice breeding for Bangladesh's agriculture.