Abstract
Summer dormancy is an important stress avoidance mechanism of cool season perennial grasses to persist well under harsh summer conditions. QTL associated with summer-dormancy related traits in tall fescue has significant breeding implications. An F1 pseudo testcross population was developed by crossing a Mediterranean (103-2) to a Continental parent (R43-64). The population was genotyped using 2,000 SSR and DArT markers. Phenotyping was done in growth chambers and in two Oklahoma, USA locations. Total length of R43-64 and 103-2 maps were 1,956 cM and 1,535 cM, respectively. Seventy-seven QTL were identified in the male and 46 in the female parent maps. The phenotypic variability explained by the QTL ranged between 9.91 and 32.67%. Among all the QTL, five summer dormancy related putative QTL were identified in R43-64 linkage groups (LGs) 4, 5, 12, 20 and 22 and two in 103-2 LGs 5 and 17. All the putative summer dormant QTL regions in male map showed pleiotropic responses and epistatic interactions with other summer dormant and stress responsive QTL regions for plant height, new leaf and dry biomass weight. The flanking markers related to the QTL reported in this study will be useful to improve tall fescue persistence in dry areas through marker-assisted breeding.
Highlights
Summer dormancy is a phenomenon, which is endogenously controlled and coupled with series of processes including growth reduction, cessation and/or senescence under non-limiting moisture conditions during summer[1]
Significant variability among the genotypes for before cut back fresh weight (BFW), before cut back dry weight (BDW), after cut back tiller number (ATN), after cut back new leaf (ANL), after cut back plant height (APHT), after cut back dry weight (ADW), return to normal growth new leaf (RNL), return to normal growth plant height (RPHT), return to normal growth dry weight (RDW), and return to normal growth average tiller weight (RATW) traits was observed in growth chamber
Treatment effect was significant for all the measured traits except after cut back average tiller weight (AATW), return to normal growth tiller number (RTN) and return to normal growth fresh weight (RFW), while genotype*treatment was non-significant for all the measured traits (Supplementary Table S1)
Summary
Summer dormancy is a phenomenon, which is endogenously controlled and coupled with series of processes including growth reduction, cessation and/or senescence under non-limiting moisture conditions during summer[1] It is an important drought avoidance mechanism of cool season perennial grasses in the Mediterranean climates to survive under harsh summer c onditions[2]. Dierking et al.[24] reported genetic linkage map of an F1 pseudo-testcross population between a Mediterranean and a Continental tall fescue genotype using SSR and Diversity Array Technology (DArT) markers. We have incorporated additional SSR marker and rebuilt the genetic linkage maps We conducted both growth chamber and field studies for phenotyping summer dormancy related traits in the population. The identified marker could be used for MAS to enhance tall fescue breeding program for summer dormancy
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