Genotype-by-environmental interaction effects on earliness, semi-dwarfism, and yield of rice (Oryza sativa L.) mutants in Tamil Nadu, India

Rice plant architecture improvement helps in the effective and efficient source-sink relationship to enhance yield. The most preferred plant architecture in rice is dwarf type. Improved White Ponni (IWP) is a tall, medium duration, released variety of Tamil Nadu, India, yielding 300 kg more than parental line White Ponni, which is suitable for second season transplanting. To induce variation in plant height to select semi-dwarf mutants, IWP was subjected to mutagenesis in 2011 using different doses of gamma rays to develop semi-dwarf and short-duration mutants. The selection was carried out in segregating populations of M-2, and an evaluation of selected better-performing mutants was done up to 70 selected mutants in M-5. Nineteen M-5 homozygous, semi-dwarf, and short-duration mutants that outperformed the IWP were evaluated in 2015-2016 across five contrasting environments of Tamil Nadu in India. The genotypes were grown in a randomized complete block design with two replications with IWP as a control. In the additive main effects and multiplicative interaction (AMMI) biplot, the analysis revealed that PC1 and PC2 accounted for 49% and 18% of the variation, respectively. Interaction principal component analysis-1 scores were observed for the mutants, viz., IWP-15-5, IWP-22-1, and IWP-30-5, indicating their superior performance. In the GGE biplot, E1 (Aduthurai), E4 (Coimbatore), and E5 (Thirupathisaram) were the ideal environments for selecting high-yielding mutants. IWP-6-5 and IWP-16-2 were the stable mutants for yield (23.59 and 24.51 g, respectively) but with a lower mean than other mutants at favorable environments. Based on the two models, E2 (Killikulam) and E3 (Madurai) were the favorable locations for exploiting high yields; IWP-30-5, IWP-22-2, and IWP-22-3 were stable across environments. These stable, high-yielding, and early maturing mutants show potential for further advancement and eventual release of new rice varieties.