Stay green behaviour of a novel mutant, PSG16 shows complex inheritance and functional relations with grain yield in rice

To ensure food security for the future, contemporary rice breeding has to harness novel secondary traits linked to higher productivity. Functional staygreen (SG) is one such trait that has shown promise by delaying senescence while improving crop productivity. Pusa-stay-green 16 (PSG 16) is a novel SG mutant that appeared in a breeding population that showed true to type breeding in subsequent generations and higher grain yield. Study of the inheritance pattern of the SG behavior in PSG16, by crossing with two non-SG parents Pusa 677 and Pusa 44 indicated a major gene inheritance in the F₂ generation. The trait was found associated with the measure of total chlorophyll content (TCC) at the physiological maturity stage. The relationship of TCC to other agronomic traits, in the segregating populations of the cross, from F₂-F₅, showed a consistent association with grain yield, suggesting the functional property of the SG trait. However, TCC showed a quantitative inheritance pattern. Additional investigations on the inheritance pattern and gene actions for the TCC revealed significant additive and dominant gene actions. The dominance superseded the additive component on an individual gene basis, thereby signifying the class variation observed under the goodness of fit test. However, a large interaction component with additive x additive gene action could be identified in trait expression. Therefore, the inheritance of SG trait was complex and deviated from the simple additive dominance pattern. A careful breeding procedure involving intermating, sib-mating and recurrent selection may be needed to utilize the trait in crop improvement. The causative loci need to be mapped for further understanding of the SG behavior of PSG16, along with in-depth physiological characterization for the functionality of the trait.