Abstract
Heat stress is one of the major abiotic factors limiting the growth of cool-season grass species during summer season. The objectives of this study were to assess genetic variations in the transcript levels of selected genes in fine fescue cultivars differing in heat tolerance, and to identify single nucleotide polymorphism (SNP) markers associated with candidate genes related to heat tolerance. Plants of 26 cultivars of five fine fescue species (Festuca spp.) were subjected to heat stress (38/33 °C, day/night temperature) in controlled environmental growth chambers. Physiological analysis including leaf chlorophyll content, photochemical efficiency, and electrolyte leakage demonstrated significant genetic variations in heat tolerance among fine fescue cultivars. The transcript levels of selected genes involved in photosynthesis (RuBisCO activase, Photosystem II CP47 reaction center protein), carbohydrate metabolism (Sucrose synthase), energy production (ATP synthase), growth regulation (Actin), oxidative response (Catalase), and stress protection (Heat shock protein 90) were positively correlated with the physiological traits for heat tolerance. SNP markers for those candidate genes exhibited heterozygosity, which could also separate heat-sensitive and heat-tolerant cultivars into clusters. The development of SNP markers for candidate genes in heat tolerance may allow marker-assisted breeding for the development of new heat-tolerant cultivars in fine fescue and other cool-season grass species.
Highlights
Heat stress is one of the primary abiotic factors limiting growth of cool-season species
The objectives of this study were to assess the genetic variation in the transcript levels of several genes related to physiological performance of fine fescue cultivars showing contrasting heat tolerances, and to identify single nucleotide polymorphism (SNP) markers associated with such candidate genes related to heat tolerance
Leaf chlorophyll content and photochemical efficiency declined significantly while electrolyte leakage increased significantly during 35 days of heat stress for all 26 cultivars based on the data collected weekly at 7, 14, 21, 28, and 35 days of heat stress, and the adverse effects of heat stress and the genetic variations in all physiological parameters were most pronounced at 35 days of heat stress
Summary
Heat stress is one of the primary abiotic factors limiting growth of cool-season species. Many genes are known to play important roles in heat tolerance [12,14,19,20], including those involved in photosynthesis (i.e., Ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCO) large subunit (RBCL), RuBisCO small subunit (RBCS), RuBisCO activase beta subunit (RCAB), Photosystem II CP47 reaction center protein (CP47), Chlorophyll a/b binding protein (CAB), Ferredoxin-NADP reductase (FNR)), energy metabolism (ATP synthase alpha subunit (ATPA), ATPase (ATPASE), Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) beta subunit (GAPDH)), stress protection (Heat shock protein 26 (HSP26), HSP70, HSP90 catalase alpha subunit (CATA)). Candidate genes with known biological functions associated with physiological traits have been found to be useful for genetic improvement in stress tolerance through either genetic modification or molecular breeding in both annual crops and perennial grasses [21,22,23,24,25]. The association of candidate genes with genetic variations for heat tolerance and markers linked to physiological traits are not well documented for perennial grass species
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