Abstract
Stem elongation is a critical phase for yield formation in wheat (Triticum aestivum). This study proposes the use of terrestrial laser scanning (TLS) for phenotyping of growth dynamics during wheat stem elongation in high temporal resolution and high throughput in the field. TLS was implemented on a novel field phenotyping platform carrying a cable suspended sensor head moveable in 3D over a 1 ha field. Canopy height was recorded on 335 winter wheat genotypes across two consecutive years. Scans were done in 3-d intervals during the stem elongation phase. Per day, 714 plots (two replications plus checks) were scanned within 3.5 h. The results showed that canopy height increased linearly with thermal time. Based on this linearity, 15 and 95% of final height were used as proxy measures for the onset and termination of stem elongation, respectively. We observed high heritability between 0.76 and 0.91 for the onset, termination and duration of stem elongation. The onset of stem elongation showed a positive covariance with the termination of stem elongation and final height indicating some regulatory dependencies. Yet there was no apparent relationship between onset and duration of stem elongation. Due to its precision, the TLS method allows to measure the dynamics of stem elongation in large sets of genotypes. This in turn offers opportunities to investigate the genetic control of the transitions between early vegetative growth, stem elongation and flowering. Understanding the genetic control of these transitions is an important milestone towards knowledge-based crop improvement.
Highlights
Stem elongation (SE) is a critical phase for yield formation in wheat (Triticum aestivum) and has been proposed as a target site to improve yield and environmental adaptation of wheat (Miralles et al 2000; Gonzalez et al 2003). 157 Page 2 of 13Physiological background SE itself is a growth trait, it has been shown to be strongly related to developmental progress in the field (Slafer et al 1995)
The average canopy height of all 335 genotypes observed in this study showed similar development in both growing seasons 2015 and 2016 (Fig. 4)
Canopy height development clearly followed a linear trend across the whole SE period
Summary
Stem elongation (SE) is a critical phase for yield formation in wheat (Triticum aestivum) and has been proposed as a target site to improve yield and environmental adaptation of wheat (Miralles et al 2000; Gonzalez et al 2003). 157 Page 2 of 13Physiological background SE itself is a growth trait, it has been shown to be strongly related to developmental progress in the field (Slafer et al 1995). SE starts after the formation of the terminal spikelet and ends with anthesis (Slafer et al 2009). Between these two events, active spike growth takes place (Slafer et al 2009). Active spike growth takes place (Slafer et al 2009) Due to this co-occurrence, the SE phase is considered to be critical for potential yield in wheat. This has been proposed quite early (Hudson 1934; Fischer 1985; Slafer et al 2001) and was widely confirmed in later years (Kirby 1988; Slafer et al 1996, 2001). Spike dry weight at anthesis is largely related to grain number per spike (Fischer 1985; Slafer et al 2001), which in turn has been found to be more yield determining than individual grain weight (Slafer et al 2001 and references cited therein), especially in connection with environmental variation of yield (Fischer 1985; Calvino and Monzon 2009)
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