Abstract
In wheat, temperature affects the timing and intensity of stem elongation. Genetic variation for this process is therefore important for adaptation. This study investigates the genetic response to temperature fluctuations during stem elongation and its relationship to phenology and height. Canopy height of 315 wheat genotypes (GABI wheat panel) was scanned twice weekly in the field phenotyping platform (FIP) of ETH Zurich using a LIDAR. Temperature response was modelled using linear regressions between stem elongation and mean temperature in each measurement interval. This led to a temperature-responsive (slope) and a temperature-irresponsive (intercept) component. The temperature response was highly heritable (H2=0.81) and positively related to a later start and end of stem elongation as well as final height. Genome-wide association mapping revealed three temperature-responsive and four temperature-irresponsive quantitative trait loci (QTLs). Furthermore, putative candidate genes for temperature-responsive QTLs were frequently related to the flowering pathway in Arabidopsis thaliana, whereas temperature-irresponsive QTLs corresponded to growth and reduced height genes. In combination with Rht and Ppd alleles, these loci, together with the loci for the timing of stem elongation, accounted for 71% of the variability in height. This demonstrates how high-throughput field phenotyping combined with environmental covariates can contribute to a smarter selection of climate-resilient crops.
Highlights
Temperature is a major abiotic factor affecting plant growth and development
We have previously demonstrated that the ETH field phenotyping platform (FIP; Kirchgessner et al, 2016) can be used to accurately track the development of canopy height in a large set of wheat genotypes using terrestrial laser scanning (Kronenberg et al, 2017)
We aimed to dissect the process towards final height into the following components: (i) temperatureindependent elongation; (ii) temperature-dependent elongation; and (iii) the duration of the elongation phase determined by the start and end of the process.To achieve this, we present a method to assess and measure these three processes under field conditions by means of high-frequency, high-throughput phenotyping of canopy height development.The resulting data were combined with genetic markers to identify quantitative trait loci (QTLs) controlling the aforementioned processes
Summary
Temperature is a major abiotic factor affecting plant growth and development. As a consequence of global warming, wheat production could decrease by 6% for each degree Celsius of global temperature increase (Asseng et al.,2015).While heat stress during critical stages can drastically reduce yield (Gibson and Paulsen, 1999; Farooq et al, 2011), warm temperatures can decrease yield by accelerating development and thereby shortening critical periods for yield formation (Fischer, 1985; Slafer and Rawson, 1994). SE is a critical phase for yield formation in wheat It occurs between the phenological stages of terminal spikelet initiation and anthesis (Slafer et al, 2015).The start of SE coincides with the transition from vegetative to reproductive development, when the apex meristem differentiates from producing leaf primordia to producing spikelet primordia (Trevaskis et al, 2007; Kamran et al, 2014). An increased duration of SE increases the number of fertile florets due to longer spike growth and higher dry matter partitioning to the spike (González et al, 2003) This in turn increases the number of grains per spike and yield (Fischer, 1985). Flowering time occurred earlier in Germany throughout the past decade, which is attributable to both increased temperature and selection for early flowering (Rezaei et al, 2018)
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