Crop plant partial resistance to plant pathogens controlled by quantitative trait loci (QTL) is desirable in cultivar development programmes because of its increased durability. Mechanisms underlying such resistance are difficult to study. We performed RNA-seq analyses for tobacco (Nicotiana tabacum) nearly isogenic lines (NILs) with and without favourable allele(s) at Phn7.1, a major QTL influencing partial resistance to the soil-borne pathogens Phytophthora nicotianae and Ralstonia solanacearum. Based upon combined analyses of transcriptome-based sequence variation and gene expression profiles, we concluded that allelic variability at the Phn7.1 locus was likely generated from homoeologous exchange, which led to deletion of low-expressing members of the SAR8.2 gene family and duplication of high-expressing SAR8.2 genes from a different subgenome of allotetraploid tobacco. The high expression of endogenous Phn7.1-associated SAR8.2 genes was correlated with observed resistance to P. nicotianae. Our findings suggest a role for genomic rearrangements in the generation of favourable genetic variability affecting resistance to pathogens in plants.

中文翻译：

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同源染色体交换解释了影响烟草土传病原体抗性的 QTL 的产生


作物对由数量性状基因座 (QTL) 控制的植物病原体的部分抗性在品种开发计划中是可取的，因为它具有更高的耐久性。这种耐药性背后的机制很难研究。我们对烟草 ( Nicotiana tabacum ) 近等基因系 (NIL) 进行了 RNA-seq 分析，其中 Phn7.1 具有或不具有有利等位基因， Phn7.1是影响对土传病原体Phytophthora nicotianae和Ralstonia solanacearum部分抗性的主要 QTL。基于对基于转录组的序列变异和基因表达谱的综合分析，我们得出结论， Phn7.1基因座的等位基因变异可能是由同源交换产生的，这导致了SAR8.2基因家族低表达成员的删除和来自异源四倍体烟草不同亚基因组的高表达SAR8.2基因的重复。内源性Phn7.1相关SAR8.2基因的高表达与观察到的P抗性相关。烟草亚科。我们的研究结果表明，基因组重排在产生有利的遗传变异性中发挥着作用，从而影响植物对病原体的抗性。