Mechanism and relevance of stay green trait in crop breeding for abiotic stress tolerance

Abstract Stay-green (SG) or delayed senescence trait is characterized by extended retention of greenness and contributes to improved carbon capture, radiation use efficiency, and resource remobilization. Significant advances have been made in our understanding of the physiological, biochemical, and genetic basis of delayed senescence. There is substantial experimental evidence for the association of stay-green with improved photosynthesis, yield, and tolerance to both biotic and abiotic stresses. A significant advancement has been made in understanding the physiological and biochemical basis providing new insights into modifications in the chlorophyll degradation pathway that ensure the extended duration of the green canopy and improved efficiency of photosynthesis. This coupled with advances in genetic and genomic resources has helped in the identification of a large number of genes/QTLs in different crops. The important SG gene SGR and its homologs have been characterized in fair detail for their role in chlorophyll degradation as well as its role in pre-senescing leaves under abiotic stress Stay-green is now increasingly used as a selection criterion in breeding programs as an indirect trait for improving resilience to various biotic and abiotic stresses. Advances in high throughput phenotyping have provided better insights into the dynamics of senescence, to delineate the differences effectively between functional and cosmetic stay-green traits. Future breeding programs will increasingly rely on harnessing natural variation in functional stay-green traits to develop climate-resilient crop varieties. This review describes the present understanding of mechanistic insights as well as its relevance to crop breeding especially under climate change scenario.