Manipulating summer dormancy to improve forage yield and seasonal distribution of tall fescue
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Tall fescue is a cool-season grass commonly used as forage. Understanding the mechanisms and genetic factors underlying summer dormancy in tall fescue can aid in a faster transfer of favorable traits across germplasm pools and speed up the process of cultivar development. In this study, we developed a potential surrogate phenotyping method for summer dormancy. The ratio of germination rate at 30°C divided by germination rate at 20°C under 24 hrs photoperiod correlates well (r = 0.7) with field dormancy rating. We re-sequenced 23 candidate genes that have been implicated in seasonal dormancy, in dormant and non-dormant checks, and developed 62 KASP markers based on nucleotide variants. Five SNP (Single Nucleotide polymorphism) markers from the genes CONSTANS and TERMINAL FLOWER, known to modulate meristem determinacy and growth, showed significant associations (p<0.05) with field summer dormancy rating scores. Another five markers derived from dormancy-associated MADS-box (DAM), auxin response factors (ARFs), and Heat shock proteins (HSPs) sequences, showed significant associations at p<0.05 with the surrogate germination phenotype (R2 = 0.13 to 0.20). These markers need to be validated in a segregating population for potential application in marker assisted selection for summer dormancy. The relation between summer dormancy and determinacy was tested. The data showed that summer dormant genotypes will go dormant only after flowering and setting seed. These findings need to be confirmed using a larger set of dormant and non-dormant populations.