Natural variation of physiological traits, molecular markers, and chlorophyll catabolic genes associated with heat tolerance in perennial ryegrass accessions

Abstract

Background Identification of genetic diversity in heat tolerance and associated traits is of great importance for improving heat tolerance in cool-season grass species. The objectives of this study were to determine genetic variations in heat tolerance associated with phenotypic and physiological traits and to identify molecular markers associated with heat tolerance in a diverse collection of perennial ryegrass (Lolium perenne L.). Results Plants of 98 accessions were subjected to heat stress (35/30 °C, day/night) or optimal growth temperature (25/20 °C) for 24 d in growth chambers. Overall heat tolerance of those accessions was ranked by principal component analysis (PCA) based on eight phenotypic and physiological traits. Among these traits, electrolyte leakage (EL), chlorophyll content (Chl), relative water content (RWC) had high correlation coefficients (− 0.858, 0.769, and 0.764, respectively) with the PCA ranking of heat tolerance. We also found expression levels of four Chl catabolic genes (CCGs), including LpNYC1, LpNOL, LpSGR, and LpPPH, were significant higher in heat sensitive ryegrass accessions then heat tolerant ones under heat stress. Furthermore, 66 pairs of simple sequence repeat (SSR) markers were used to perform association analysis based on the PCA result. The population structure of ryegrass can be grouped into three clusters, and accessions in cluster C were relatively more heat tolerant than those in cluster A and B. SSR markers significantly associated with above-mentioned traits were identified (R2 > 0.05, p < 0.01)., including two pairs of markers located on chromosome 4 in association with Chl content and another four pairs of markers in association with EL. Conclusion The result not only identified useful physiological parameters, including EL, Chl content, and RWC, and their associated SSR markers for heat-tolerance breeding of perennial ryegrass, but also highlighted the involvement of Chl catabolism in ryegrass heat tolerance. Such knowledge is of significance for heat-tolerance breeding and heat tolerance mechanisms in perennial ryegrass as well as in other cool-season grass species.

Adaptability to High Temperature and Stay-Green Genotypes Associated With Variations in Antioxidant, Chlorophyll Metabolism, and γ-Aminobutyric Acid Accumulation in Creeping Bentgrass Species

“…Pearson correlation coefficients analysis showed that Chl content, OP, or EL had first, second, or third highest correlation coefficient with the SFVA ranking of heat tolerance among the 41 creeping bentgrass accessions, respectively. A recent study on natural variation of heat tolerance among 98 perennial ryegrass accessions also demonstrated that EL and Chl content were the top two evaluation parameters that exhibited high correlation coefficients with heat tolerance (Zhang et al, 2020). Thus, Chl and EL could be used as critical traits for a quick identification of heat tolerance among a large number of cool-season grass germplasms.…”

The Alkali Tolerance of Broomcorn Millet (Panicum miliaceum L.) at the Germination and Seedling Stage: The Case of 296 Broomcorn Millet Genotypes

“…F was used as the comprehensive evaluation value of the alkali resistance of the BM genotypes. The higher the F -value, the stronger the resistance to alkali stress of the BM; the lower the F -value, the weaker the resistance to alkali stress of the BM (Zhang et al, 2020 ).…”

Transcriptome characterization of candidate genes for heat tolerance in perennial ryegrass after exogenous methyl Jasmonate application

“…In addition, MeJA pretreatment reduced the expression level of chlorophyll degradation related genes. Previous study found that the expression levels of several Chl catabolic genes in heat sensitive ryegrass were significantly higher than that in heat resistant ryegrass under heat stress [ 5 ]. It appears that exogenous MeJA may delay leaf senescence in perennial ryegrass by affecting the expression level of genes in the chlorophyll biosynthesis and degradation pathways under heat stress, thus, improving the heat tolerance of perennial ryegrass.…”

“…In addition, perennial ryegrass provides benefits on ecosystems such as promoting carbon assimilation, soil protection, and nutrient cycling [ 3 ]. However, perennial ryegrass is generally heat-sensitive, and high temperature is a major factor limiting its performance and utilization in many areas including temperate regions where a periodic heat stress can occur during the summertime [ 4 , 5 ]. Thus, a better understanding of heat tolerance mechanisms will help to improve grass management and facilitate breeding programs for creating heat tolerant varieties of perennial ryegrass.…”