Natural Selection Causes Adaptive Genetic Resistance in Wild Emmer Wheat against Powdery Mildew at “Evolution Canyon” Microsite, Mt. Carmel, Israel

Abstract

Background“Evolution Canyon” (ECI) at Lower Nahal Oren, Mount Carmel, Israel, is an optimal natural microscale model for unraveling evolution in action highlighting the basic evolutionary processes of adaptation and speciation. A major model organism in ECI is wild emmer, Triticum dicoccoides, the progenitor of cultivated wheat, which displays dramatic interslope adaptive and speciational divergence on the tropical-xeric “African” slope (AS) and the temperate-mesic “European” slope (ES), separated on average by 250 m.MethodsWe examined 278 single sequence repeats (SSRs) and the phenotype diversity of the resistance to powdery mildew between the opposite slopes. Furthermore, 18 phenotypes on the AS and 20 phenotypes on the ES, were inoculated by both Bgt E09 and a mixture of powdery mildew races.ResultsIn the experiment of genetic diversity, very little polymorphism was identified intra-slope in the accessions from both the AS or ES. By contrast, 148 pairs of SSR primers (53.23%) amplified polymorphic products between the phenotypes of AS and ES. There are some differences between the two wild emmer wheat genomes and the inter-slope SSR polymorphic products between genome A and B. Interestingly, all wild emmer types growing on the south-facing slope (SFS=AS) were susceptible to a composite of Blumeria graminis, while the ones growing on the north-facing slope (NFS=ES) were highly resistant to Blumeria graminis at both seedling and adult stages.Conclusion/SignificanceRemarkable inter-slope evolutionary divergent processes occur in wild emmer wheat, T. dicoccoides at EC I, despite the shot average distance of 250 meters. The AS, a dry and hot slope, did not develop resistance to powdery mildew, whereas the ES, a cool and humid slope, did develop resistance since the disease stress was strong there. This is a remarkable demonstration in host-pathogen interaction on how resistance develops when stress causes an adaptive result at a micro-scale distance.

Adaptive evolution of benzoxazinoids in wild emmer wheat, Triticum dicoccoides, at "Evolution Canyon", Mount Carmel, Israel

“…Additionally, according to this research we can learn and better understand chemical evolution. Importantly, we conclude that powdery mildew research [ 32 ] can highlight our current results. The ES at ECI appears to be a cradle for the evolution of disease resistance.…”

“…The ES at ECI appears to be a cradle for the evolution of disease resistance. Both, Yin et al [ 32 ] and the current study indicate that a microscale model like Evolution Canyon can be a fitting host-pathogen model in the evolution of resistance against pathogens and is also a model of biodiversity evolution, adaptation and incipient sympatric ecological speciation.…”

“…Moreover, experiments conducted on cereals showed that DIMBOA levels in moist and hydrated soil and humid air, such as on the ES at ECI were higher than those detected in a dry habitat [ 29 ]. As such, since the humid and cool ES represents a temperate and forested slope, only seedlings collected at the ES had high amounts of DIMBOA but none were found in seedlings from AS seeds, possibly as the result of many more pathogenic organisms such as fungi [ 30 – 32 ]. The abundance of fungi, such as powdery mildew and rusts on the ES due to cool and humid environment, would cause plants in this temperate microclimate [ 32 – 35 ] to develop the genetic ability to produce more defense compounds like DIBOA and DIMBOA as a protective adaptation against environmental biotic threats [ 32 ].…”

“…Remarkably, Yin et al [32} did research on wild emmer wheat at the Evolution Canyon microsite at Mount Carmel, Israel, and revealed that all plants grown on the AS (dry and hot slope) did not develop resistance and were susceptible to powdery mildew, a common plant disease, whereas plants derived from the ES (cool and humid slope) developed genetic disease resistance against powdery mildew. This research [ 32 ] showed that a local ecological stress on the ES caused by microclimatic interslope divergence [ 1 ] can generate adaptive evolutionary genome responses at micro scale reinforcing fitness and suggesting continuity between micro and macro–evolution on a regional or global scale. Additionally, according to this research we can learn and better understand chemical evolution.…”

Solar Radiation-Associated Adaptive SNP Genetic Differentiation in Wild Emmer Wheat, Triticum dicoccoides

“…Ecological diversification between habitats favors local adaptation. Environmental factors, such as water availability, light intensity, soil composition as well as surrounding biota, may exert diverse selection that might drive evolutionary divergence of plant populations (Peleg et al, 2008; Ren et al, 2013a; Yin et al, 2015). Of all the environmental factors, solar radiation is perhaps the most spatially and temporally heterogeneous (Martínez-Ferri et al, 2001; Nevo, 2015).…”