Pinus monticola pathogenesis-related gene PmPR10-2 alleles as defense candidates for stem quantitative disease resistance against white pine blister rust (Cronartium ribicola)

Research paper by Jun-Jun Liu, Craig Hammett, Richard A. Sniezko

Indexed on: 23 Sep '12Published on: 23 Sep '12Published in: Tree Genetics & Genomes


White pine blister rust, caused by the invasive fungus Cronartium ribicola, has been responsible for extremely high mortality of native western white pine (Pinus monticola) and other five-needle pines in natural stands throughout western North America. The presence of this non-native fungus has also led to greatly restricted use of western white pine for reforestation. A few families of defense proteins have been found as functional candidates involved in tree resistance to rust infection. Here we report genetic variation of a gene encoding a family 10 pathogenesis-related (PR) protein (PmPR10-2) in open-pollinated seed families with different levels of stem quantitative disease resistance (QDR). Six novel alleles and five common genotypes were identified inside the PmPR10-2 locus: these genetic variations included 33 single nucleotide polymorphisms (SNPs) throughout the gene regions and copy variation of a rare octanucleotide simple sequence repeat (SSR), 5′-AATTATTT-3′, in the gene intron. PmPR10-2 exhibited a moderate level (average r2 = 0.42) of linkage disequilibrium. Two-thirds of the identified SNPs and the SSR marker were significantly associated with stem QDR levels. The PmPR10-2 genotype (H3:H3) exhibited the highest level of stem QDR (P < 0.01). Cost-effective and co-dominant SSR markers were developed and used for genotyping the PmPR10-2 locus using simple PCR, providing a potential molecular tool for accelerating screening efforts of white pine resistance against C. ribicola.