Staying Alive or Going to Die During Terminal Senescence—An Enigma Surrounding Yield Stability

Abstract

Breeding programs with the aim to enhance yield productivity under abiotic stress conditions during the reproductive stage of crops is a top priority in the era of climate change. However, the choice of exploring stay-green or senescence phenotypes, which represent an opposing physiological bearing, are explored in cereal breeding programs for enhanced yield stability to a different extent. Thus, the consideration of stay-green or senescence phenotypes is still an ongoing debate and has not been comprehensively addressed. In this review, we provide arguments for designing a target phenotype to mitigate abiotic stresses during pre- and post-anthesis in cereals with a focus on hormonal balances regulating stay-green phenotype versus remobilization. The two major hypothesis for grain yield improvement are (i) the importance of the stay-green trait to elevate grain number under pre-anthesis and anthesis stress and (ii) fine tuning the regulatory and molecular physiological mechanisms to accelerate nutrient remobilization to optimize grain quality and seed weight under post-anthesis stress. We highlight why a cautious balance in the phenotype design is essential. While stay-green phenotypes promise to be ideal for developing stress-tolerant lines during pre-anthesis and fertilization to enhance grain number and yield per se, fine-tuning efficient remobilizing behavior during seed filling might optimize grain weight, grain quality and nutrient efficiency. The proposed model provides novel and focused directions for cereal stress breeding programs to ensure better seed-set and efficient grain-filling in cereals under terminal drought and heat stress exposure.

Phenotypic and metabolic plasticity shapes life‐history strategies under combinations of abiotic stresses

“…The prolonged stress conditions, imposed under S & D and S & D & H, severely curtailed photosynthesis capacity and shifted the balance from maintenance and reproduction toward defense processes throughout the plants’ life history. As a consequence of the decreased photosynthesis and culm length (Shaar‐Moshe et al., ), these plants are expected to contain less stem reserves (Borrell, Incoll, & Dalling, ) that are essential for grain filling and source‐sink homeostasis (Jagadish, Kishor, Bahuguna, von Wiren, & Sreenivasulu, ).…”

“…Under stress conditions, which diminish photosynthesis capacity of source tissues, grain filling is largely dependent on remobilization of stem reserves (Gallagher, Biscoe, & Hunter, 1976 (Borrell, Incoll, & Dalling, 1993) that are essential for grain filling and source-sink homeostasis (Jagadish, Kishor, Bahuguna, von Wiren, & Sreenivasulu, 2015). Table S3), due to a decreased demand (Hummel et al, 2010).…”

Phenotypic and metabolic plasticity shapes life-history strategies under combinations of abiotic stresses

“…The prolonged stress conditions, imposed under S & D and S & D & H, severely curtailed photosynthesis capacity and shifted the balance from maintenance and reproduction towards defense processes throughout the plants’ life-history. As a consequence of the decreased photosynthesis and culm length (Shaar-Moshe et al, 2017), these plants are expected to contain less stem reserves (Borrell et al, 1993) that are essential for grain filling and source-sink homeostasis (Jagadish et al, 2015).…”

Total Synthesis and Biological Evaluation of Zealactone 1a/b

“…Since leaf senescence is associated with crop productivity, chemical controlling leaf senescence enables accelerating nutrients relocation, which leads to optimization of grain quality and quantity. [39] Leaf senescence is regulated by several plant hormones and it has recently been reported that strigolactones can also accelerate leaf senescence through the D14-dependent pathway. [40][41][42] Herein, we assessed synthetic non-canonical strigolactones induced leaf senescence of corn by following the previously developed protocol.…”