QTL mapping of winter dormancy and associated traits in two switchgrass pseudo-F1 populations: lowland x lowland and lowland x upland

Abstract

Background Switchgrass (Panicum virgatum) undergoes seasonal growth changes based on the perception of photoperiod and temperature. It transitions to winter dormancy in early fall, breaks dormancy in the spring, and resume the cycle starting from flowering which is the cue for senescence. The length of growing season can impact the biomass accumulation and yield. In this study, we conducted QTL mapping of winter dormancy measured by fall regrowth height (FRH) and normalized difference vegetation index (NDVI), spring emergence (SE), and flowering date (FD) in two bi-parental pseudo-F1 populations derived from crosses between the lowland AP13 with the lowland B6 (AB) with 285 progenies, and the lowland B6 with the upland VS16 (BV) with 227 progenies. Methods Pearson correlation coefficient between phenotypic traits was calculated to determine if some traits can be as surrogates for other traits. Broad-sense heritabilities were calculated to determine the inheritance, and QTL mapping was conducted for two-years phenotypic data to identify QTLs associated with the trais. Results We identified 18 QTLs for FRH, 18 QTLs for NDVI, 21 QTLs for SE, and 30 QTLs for FD. The ranges of percent variance explained by these QTLs varied between 4.21–23.27% for FRH, 4.47–24.06% for NDVI, 4.35–32.77% for SE, and 4.61–29.74% for FD. A higher number of QTL was discovered in the BV population, suggesting more variants in the lowland x upland population contributing to the expression of seasonal dormancy underlying traits. We identified 9 regions of colocalized QTL with possible pleiotropic gene action. The positive correlation between FRH or NDVI with dry biomass weight suggests that winter dormancy level could affect switchgrass biomass yield. The medium to high heritability levels of FRH (0.55–0.64 H2) and NDVI (0.30–0.61 H2) support the possibility of using the traits for indirect selection for biomass yield. Conclusion Markers found within the significant QTL interval can serve as genomic resource for breeding non-dormant and semi-dormant switchgrass cultivars for the southern regions, where growers can benefit from the longer production season.