Floret site utilization and reproductive tiller number are primary components of grain yield in intermediate wheatgrass spaced plants

Abstract

Perennial plants provide extensive environmental services and increasing their prevalence on the agricultural landscape is one way to improve sustainability. Direct domestication of intermediate wheatgrass [Thinopyrum intermedium; (Host) Barkworth & D.R. Dewey] as a perennial grain crop is underway, and selection has focused primarily on improving seed size and grain yield.

Nested association mapping reveals the genetic architecture of spike emergence and anthesis timing in intermediate wheatgrass

“…If spike length is already routinely collected, spike emergence may be an easier method for assessing flowering time, but caution should be taken to measure it around 50% emergence so that a linear relationship exists between the two events. We previously reported that the two measures of flowering time appear to have a slightly different influence on grain yield in spaced plants ( Altendorf et al 2020 ), but no QTL regions detected in the present study appeared to be completely unique to one trait or the other.…”

“…Because an initial linear model analysis across environments revealed highly significant interactions, we analyzed all unique year by location combinations ( n = 4; environments hereafter) separately. This decision was further supported by differences in plant age between 2017 and 2018, as well as major differences in climate and GDD accumulation between STP and TLI, and a severe drought in 2018 at TLI ( Altendorf et al 2020 ). Parental means were calculated and plotted alongside emmeans for progeny genotypes using ggplot2 ( Wickham 2016 ).…”

“…, ∼5 cm), the mean of two spikes was recorded. Harvesting procedures were previously outlined in Altendorf et al (2020) . After harvest, three spikes were aligned end-to-end (from tip of most apical spikelet to base of the most basal spikelet, a spikelet defined as having glumes and at least one floret) along a measuring tape and total length was recorded and divided by three to obtain the mean.…”

“…All phenotypic data analyses were conducted in R v3.6.1 ( R Core Team 2020 ). In a separate analysis of yield component traits, we previously reported the calculation of estimated marginal means (“emmeans”) for each genet nested within family for both spike emergence percent and anthesis, as well as correlations between traits, and both broad and narrow sense heritability estimates ( Lenth 2018 ; Altendorf et al 2020 ). Because an initial linear model analysis across environments revealed highly significant interactions, we analyzed all unique year by location combinations ( n = 4; environments hereafter) separately.…”

“…Including significant markers from QTL mapping studies as co-factors in genomic selection models has been shown to increase predictive ability and increases the frequency of favorable alleles ( Zhang et al 2017 ; Bajgain et al 2019a , b ). However, IWG is still susceptible to seed shattering ( Larson et al 2019 ), has low threshability ( Zhang et al 2016 ), is tall and prone to stem lodging ( Frahm et al 2018 ), and has low-floret site utilization that may contribute to low yields ( Altendorf et al 2020 ). An improved understanding of the genetic architecture of these important traits has the potential to further increase efficiency and precision in IWG breeding efforts through genomics assisted breeding, but the difficulty lies in the fact that relatively few marker-trait association studies have been conducted in IWG and the genetic control of many important traits remains poorly understood.…”