Abstract
In this review, we present a comprehensive revisit of past research and advances developed on the stay-green (SG) paradigm. The study aims to provide an application-focused review of the SG phenotypes as crop residuals for bioenergy. Little is known about the SG trait as a germplasm enhancer resource for energy storage as a system for alternative energy. Initially described as a single locus recessive trait, SG was shortly after reported as a quantitative trait governed by complex physiological and metabolic networks including chlorophyll efficiency, nitrogen contents, nutrient remobilization and source-sink balance. Together with the fact that phenotyping efforts have improved rapidly in the last decade, new approaches based on sensing technologies have had an impact in SG identification. Since SG is linked to delayed senescence, we present a review of the term senescence applied to crop residuals and bioenergy. Firstly, we discuss the idiosyncrasy of senescence. Secondly, we present biological processes that determine the fate of senescence. Thirdly, we present the genetics underlying SG for crop-trait improvement in different crops. Further, this review explores the potential uses of senescence for bioenergy crops. Finally, we discuss how high-throughput phenotyping methods assist new technologies such as genomic selection in a cost-efficient manner.
Highlights
The genotypes with the Stay green (SG) characteristic maintain greenness during the final stage of leaf development due to coordinated genetic mechanisms that regulate the transition from nutrient assimilation to nutrient remobilization [1,2] and the biochemical processes of chlorophyll breakdown during leaf senescence [3] (Figure 1)
We address the role of senescence or SG as a highly genetic controlled trait that helps plant to respond to biotic and environmental stresses and discuss the extent to which bioenergy crops can benefit from this paradigmatic trait
The genetic and physiological routes to SG phenotype are quite diverse among species [11], it is directly related to chlorophyll content of leaves since loss of chlorophyll leads to visible symptoms of senescence (Figures 1 and 2)
Summary
The genotypes with the Stay green (SG) characteristic maintain greenness during the final stage of leaf development due to coordinated genetic mechanisms that regulate the transition from nutrient assimilation to nutrient remobilization [1,2] and the biochemical processes of chlorophyll breakdown during leaf senescence [3] (Figure 1). We will focus on the whole plant senescence of herbaceous crops and its relevance for the production of bioenergy. Plant senescence is often described as a paradox because this “survival” strategy encourages the death of the organism; Schippers et al [6] described this paradox as living to die and dying to live. We address the role of senescence or SG as a highly genetic controlled trait that helps plant to respond to biotic and environmental stresses and discuss the extent to which bioenergy crops can benefit from this paradigmatic trait. Energies 2020, 13, x FOR PEER REVIEW senescence remobilization of C and N from “green” tissues to fasten grain-filling These physiological changes alter C and N metabolism by impairing translocation mechanisms leading to a source-sink unbalanced distribution.
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