A genome‐wide analysis suggests pleiotropic effects of Green Revolution genes on shade avoidance in wheat

Abstract

A classic example of phenotypic plasticity in plants is the suit of phenotypic responses induced by a change in the ratio of red to far‐red light (R∶FR) as a result of shading, also known as the shade avoidance syndrome (SAS). While the adaptive consequences of this syndrome have been extensively discussed in natural ecosystems, how SAS varies within crop populations and how SAS evolved during crop domestication and breeding remain poorly known. In this study, we grew a panel of 180 durum wheat (Triticum turgidum ssp. durum) genotypes spanning diversity from wild, early domesticated, and elite genetic compartments under two light treatments: low R:FR light (shaded treatment) and high R:FR light (unshaded treatment). We first quantified the genetic variability of SAS, here measured as a change in plant height at the seedling stage. We then dissected the genetic basis of this variation through genome‐wide association mapping. Genotypes grown in shaded conditions were taller than those grown under unshaded conditions. Interaction between light quality and genotype did not affect plant height. We found six QTLs affecting plant height. Three significantly interacted with light quality among which the well‐known Rht1 gene introgressed in elite germplasm during the Green Revolution. Interestingly at three loci, short genotypes systematically expressed reduced SAS, suggesting a positive genetic correlation between plant height and plant height plasticity. Overall, our study sheds light on the evolutionary history of crops and illustrates the relevance of genetic approaches to tackle agricultural challenges.

Agroecological genetics of biomass allocation in wheat uncovers genotype interactions with canopy shade and plant size

“…The opposing effect of canopy shade and plant size on biomass allocation may be due to the dual effect of the green filter on light spectra and light intensity. For example, in genotypes carrying the GA‐sensitive wild allele, the low red/far‐red ratio may increase the stem mass fraction through stem elongation (Colombo et al ., 2022), while the lower light intensity induces a more significant restriction on stem growth due to the allometric trajectory of the genotypes carrying the wild allele.…”

Niche construction and the environmental term of the price equation: How natural selection changes when organisms alter their environments

“…In other words, the crop environments as well as their genotypes have been “engineered” by agricultural geneticists: enhanced output depends on “technologies required to realize the genetic potential of new crop varieties and hybrids…” including the 955% increase in N fertilizers used in world agriculture since 1961 (Pellegrini & Fernández, 2018). This “genetic potential” is realized only in human‐constructed high‐fitness crop environments because these varieties often show fitness genotype by environment variation, producing lower yields than traditional varieties in the absence of chemical pesticides and other inputs (Colombo et al, 2022). For natural systems, biodiversity conservation requires preservation of a species' niche‐constructed environments as well as its genetic potential (Boogert et al, 2006; Fogarty & Wade, 2022).…”

Shift in beneficial interactions during crop evolution

“…For instance, the teosinte allele of the TB1 gene introgressed in a modern maize background confers greater phenotypic plasticity and responsiveness to light than the maize allele (Lukens & Doebley, 1999 ). In wheat, recent results suggest that Green Revolution genes introduced in the 1960s to improve fertilizer responsiveness might also have reduced plant height plasticity (Colombo et al, 2022 ). Similarly, in barley and wheat, wild versus domesticated forms, and landraces versus modern cultivars, display greater plasticity in root traits in response to heterogeneous nutrient availability (Grossman & Rice, 2012 ).…”