Canadian Forest Service Publications

Association analysis identifies Melampsora x columbiana poplar leaf rust resistance SNPs. 2013. La Mantia, J.; Klapste, J.; El-Kassaby, Y.A.; Azam, S.; Guy, R.D.; Douglas, C.J.; Mansfield, S.D.; Hamelin, R. PLOS ONE 8:e78423.

Year: 2013

Available from: Laurentian Forestry Centre

Catalog ID: 35232

Language: English

CFS Availability: PDF (request by e-mail)

Abstract

Populus species are currently being domesticated through intensive time- and resource-dependent programs for utilization in phytoremediation, wood and paper products, and conversion to biofuels. Poplar leaf rust disease can greatly reduce wood volume. Genetic resistance is effective in reducing economic losses but major resistance loci have been race-specific and can be readily defeated by the pathogen. Developing durable disease resistance requires the identification of non-race-specific loci. In the presented study, area under the disease progress curve was calculated from natural infection of Melampsora x columbiana in three consecutive years. Association analysis was performed using 412 P. trichocarpa clones genotyped with 29,355 SNPs covering 3,543 genes. We found 40 SNPs within 26 unique genes significantly associated (permutated P<0.05) with poplar rust severity. Moreover, two SNPs were repeated in all three years suggesting non-race-specificity and three additional SNPs were differentially expressed in other poplar rust interactions. These five SNPs were found in genes that have orthologs in Arabidopsis with functionality in pathogen induced transcriptome reprogramming, Ca2+/calmodulin and salicylic acid signaling, and tolerance to reactive oxygen species. The additive effect of non-R gene functional variants may constitute high levels of durable poplar leaf rust resistance. Therefore, these findings are of significance for speeding the genetic improvement of this long-lived, economically important organism.

Plain Language Summary

Poplar is a fast-growing species widely used by the forest industry and in the emerging biomass industry. It is also being increasingly used for phytoremediation (the use of plants for rehabilitation of disturbed sites) and for the production of biofuels. A causal fungus, poplar leaf rust, threatens poplars, which could cause a significant decrease in the volume of wood produced.

Poplars possess a certain level of resistance to this pathogen. While this resistance is embedded in the poplar’s genetic makeup, it is often specific to a particular strain and often short-lived, as it can be quickly thwarted by the introduction of new virulence factors by the causal fungus.

This study aimed to better understand the relationship between black cottonwood (Populus trichocarpa) and poplar leaf rust Melampsora x columbiana. Its purpose was to identify resistance genes in poplar that might be effective against all strains of rust rather than one strain in particular, thus leading to increased resistance. Using genomics, the researchers identified 26 genes associated with resistance to several strains of rust. This discovery could help to produce poplars with heightened resistance to poplar leaf rust.

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