Stay-green (SG) refers to the heritable delayed foliar senescence. It is a secondary trait that enables crop plants to maintain their green leaves and photosynthetic capacity for a longer time after anthesis, especially under drought and heat stress conditions4. SG trait was recognized as a superior characteristic for commercially bred cereals to overcome the current yield stagnation in alliance with yield adaptability and stability4.

SG is of two types 1) Functional stay-green 2) Cosmetic stay-green. In functional stay-green, the transition from the carbon capture period to the nitrogen mobilization (senescence) phase of canopy development is delayed, or the senescence syndrome proceeds slowly. Breeding for functional stay green trait has contributed in improving crop yields, particularly when it is combined with other useful traits. Elucidating the molecular and physiological mechanisms associated with stay green trait expected to be key in defeating the stagnation in productivity associated with adaptation to environmental stress4.

In cosmetic stay‐green, a lesion interferes with an early step in chlorophyll catabolism. It is important for quality traits in many specialty crops, and they have been selected for their novel appearance during growth. Cosmetic stay‐green mutants were first identified in forage/turf grass species and rice, and have since been identified in tomato, pepper, and common bean. In nearly every case, a homolog of the stay‐green gene (SGR) is involved4.

Stay-green traits has enabled stabilize the yield attributes under combined heat and drought stress in wheat by retaining higher amount of chlorophyll, photosynthesis rate and leaf area duration at the anthesis stage under combined stress condition3. Stay-green trait in groundnut has been reported to have positive association with early leaf spot (ELS) and late leaf spot (LLS) diseases and, hence has the ability to confer resistance to leaf spot disease in groundnut1.

Stay-green QTLs have been identified in several crops including sorghum, wheat, rice etc. Advanced breeding approaches have enabled breeders to transfer the identified stay-green QTL to the genotype having good agronomic background. Incorporation of stay-green trait in a genotype expected to increase the grain yield and market value and thus contribute to our national economy2. There is a need to explore stay-green trait extensively in breeding programmes in different crops to harness genetic progress in grain yield, quality, disease resistance and tolerance to abiotic stresses. Stay-green trait in combination with other useful traits may provide the solution against heat and drought stresses.

References:

 1DANFUL, R., KASSIM, Y.B., PUOZAA, D.K., OTENG-FRIMPONG, R., RASHEED, M.A., WIREKO-KENA, A. AND AKROMAH, R., 2019, Genetics of stay-green trait and its association with leaf spot tolerance and pod yield in groundnut. Int. J. Agron., 2019.

2KASSAHUN, B., BIDINGER, F.R., HASH, C.T. AND KURUVINASHETTI, M.S., 2010, Stay-green expression in early generation sorghum [Sorghum bicolor (L.) Moench] QTL introgression lines. Euphytica, 172 (3): 351-362.

3KUMAR, R., HARIKRISHNA, BARMAN, D., GHIMIRE, O.P., GURUMURTHY, S., SINGH, P.K., CHINNUSAMY, V., PADARIA, J.C. AND ARORA, A., 2022, Stay-green trait serves as yield stability attribute under combined heat and drought stress in wheat (Triticum aestivum L.). Plant Growth Regul.,1: 1-12.

4MYERS, J.R., ALJADI, M. AND BREWER, L., 2018, The importance of cosmetic stay‐green in specialty crops. Plant Breed. Rev., 42: 219-256.