“Genetics and molecular nature of stay green traits in crop improvement”

   In current agricultural scenario, there is increasing demand for food, so the plant breeders are thinking and investing not only in the traditional criteria, such as yield, but also in the selection of genotypes with high productive efficiency by understanding the crop physiology and stress adaptation in order to meet the increasing demand. A number of physiological and morphological traits related to increasing yield are yet to be fully exploited in modern cultivars.

Stay-green is the term given to a variant in which senescence is delayed in comparison to a standard reference genotype. Delay of leaf senescence, also known as stay-green character, has been identified as an important component in the genetic improvement of several crops to promote stress tolerance, yield gain and to improve the fodder quality. Senescence is a physiological process where there is a mobilization of nutrient reserves and cytokinins into fruits and seeds. It is a fact that senescence is associated with the balance between hormones such as cytokinins and ethylene, change in them showed changes in the timing of senescence. By understanding the physiological and molecular mechanisms concomitant with “STAY-GREEN” trait or delayed leaf senescence of plants under heat stress, with a certain focus on the hormonal pathways, may be a key to break the plateau of productivity associated with adaptation to high temperature (Abdelrahman et. al., 2017). Stay-green results when the plant’s normal process of senescence is disrupted. When mutants disrupt the chlorophyll degradation it leads to stay-green phenotype.

Staygreen trait is associated with biotic and abiotic stress resistance, lodging resistance, increased yield and quality under stress condition. In this path triple disease resistances in Gy14 cucumber genotype were controlled by the cucumber staygreen (CsSGR) gene. Genes in the chlorophyll degradation pathway showed differential expression between resistant and susceptible lines in response to pathogen inoculation (Wang et. al., 2018). Several genes and QTLs have been identified in different crops using several bi-parental populations and genomic approaches. These QTLs are currently being used for introgression in a number of genetic backgrounds. Single mutant in the region of MtSGR leads stay green phenotype in Medicago truncatula. In rice twenty-five known genes and pleiotropic candidate gene OsSG1 accounted for natural variation in CC and SG. (Yan Zhao et.al. 2019).

Now a day increasing genomic technologies like gene silencing, transcriptome analysis will be beneficial for development of different stay green phenotype in different crops which finally helps to improve the fodder quality and to break yield plateau which we reached now in all crops.

Reference:

ABDELRAHMAN, M., EL-SAYED, M., JOGAIAH, S., BURRITT, D. J., TRAN, L. P., 2017, The “stay-green” trait and phytohormone signalling networks in plants under heat stress. Plant Cell Reports. 36(7): 1009–1025.

WANG, Y., TAN, J., WU, Z., LANGENBERG, K. V., WEHNER, T. C., WEN, C., ZHENG, X., OWENS, K., THORNTON, A., BANG, H. H., HOEFT, E., KRAAN, P. A. G., JOS, S., PAN, J. AND WENG, Y., 2018., Staygreen, stay healthy: a loss-of-susceptibility mutation in the staygreen gene provides durable, broad-spectrum disease resistances for over 50 years of us cucumber production. New phytologist. 221: 415–430.

ZHAO, Y., QIANG, C., WANG, X., CHEN, Y., DENG, J., JIANG, C., SUN, X., CHEN, H., LI, J., PIAO, W., ZHU, X., ZHANG, Z., ZHANG, H., L, Z. AND LI. J., 2019., New alleles for chlorophyll content and stay-green traits revealed by a genome wide association study in rice (Oryza sativa). Nature. 9: 254.