Genomic prediction of switchgrass winter survivorship across diverse lowland populations

Abstract

In the North-Central United States lowland ecotype switchgrass can increase yield by up to 50% compared to locally adapted but early-flowering cultivars. However, lowland ecotypes are not winter tolerant. The mechanism for winter damage is unknown but previously has been associated with late flowering time. This study investigated heading date (measured for two years) and winter survivorship (measured for three years) in a multi-generation population generated from two winter-hardy lowland individuals and diverse southern lowland populations. Sequencing data (311,776 markers) from 1,306 individuals were used to evaluate genome-wide trait prediction through cross-validation and progeny prediction (n=52). Genetic variance for heading date and winter survivorship was additive with high narrow-sense heritability (0.64 and 0.71, respectively) and reliability (0.68 and 0.76, respectively). The initial negative correlation between winter survivorship and heading date degraded across generations (F1 r=-0.43, pseudo-F2 r=-0.28, pseudo-F2 progeny r=-0.15). Within-family predictive ability was moderately high for heading date and winter survivorship (0.53 and 0.52, respectively). A multi-trait model did not improve predictive ability for either trait. Progeny predictive ability was 0.71 for winter survivorship and 0.53 for heading date. These results suggest that lowland ecotype populations can obtain sufficient survival rates in the northern United States with two or three cycles of effective selection. Despite accurate genomic prediction, naturally occurring winter mortality successfully isolated winter tolerant genotypes and appears to be an efficient method to develop high-yielding, cold-tolerant switchgrass cultivars.

Divergent Metabolic Changes in Rhizomes of Lowland and Upland Switchgrass (Panicum virgatum) from Early Season through Dormancy Onset

“…Overall, these data support a delay in the dormancy transition in the lowland cultivar Kanlow relative to the upland cultivar Summer as suggested earlier [12,21]. Recently, genomic selection was used to identify interactions between flowering (heading dates) and winter survival in diverse lowland switchgrass populations [32]. Although positive predictive ability was determined for both traits, the mortality of plants affected by winter successfully identified cold-tolerant genotypes.…”