Understanding the complexity of the vine plant’s response to water deficit represents a major challenge for sustainable winegrowing. Regulation of water use requires a coordinated action between scions and rootstocks on which cultivars are generally grafted to cope with phylloxera infestations. In this regard, a genome-wide association study (GWAS) approach was applied on an ‘ad hoc’ association mapping panel including different Vitis species, in order to dissect the genetic basis of transpiration-related traits and to identify genomic regions of grape rootstocks associated with drought tolerance mechanisms. The panel was genotyped with the GrapeReSeq Illumina 20 K SNP array and SSR markers, and infrared thermography was applied to estimate stomatal conductance values during progressive water deficit. In the association panel the level of genetic diversity was substantially lower for SNPs loci (0.32) than for SSR (0.87). GWAS detected 24 significant marker-trait associations along the various stages of drought-stress experiment and 13 candidate genes with a feasible role in drought response were identified. Gene expression analysis proved that three of these genes (VIT_13s0019g03040, VIT_17s0000g08960, VIT_18s0001g15390) were actually induced by drought stress. Genetic variation of VIT_17s0000g08960 coding for a raffinose synthase was further investigated by resequencing the gene of 85 individuals since a SNP located in the region (chr17_10,497,222_C_T) was significantly associated with stomatal conductance. Our results represent a step forward towards the dissection of genetic basis that modulate the response to water deprivation in grape rootstocks. The knowledge derived from this study may be useful to exploit genotypic and phenotypic diversity in practical applications and to assist further investigations.

中文翻译：

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葡萄属干旱胁迫下与气孔导度相关的候选基因和SNP

了解藤本植物对缺水反应的复杂性是可持续葡萄种植的一项重大挑战。用水调节需要接穗和砧木之间的协调行动，通常嫁接栽培品种以应对根瘤蚜虫害。在这方面，全基因组关联研究 (GWAS) 方法应用于包括不同葡萄品种的“临时”关联映射面板，以剖析蒸腾相关性状的遗传基础并确定葡萄砧木的基因组区域与耐旱机制有关。该面板使用 GrapeReSeq Illumina 20 K SNP 阵列和 SSR 标记进行基因分型，并应用红外热成像来估计渐进式缺水期间的气孔导度值。在关联面板中，SNP 位点的遗传多样性水平 (0.32) 远低于 SSR (0.87)。GWAS 在干旱胁迫实验的各个阶段检测到 24 个显着的标记-性状关联，并确定了 13 个在干旱响应中具有可行作用的候选基因。基因表达分析证明，其中三个基因（VIT_13s0019g03040、VIT_17s0000g08960、VIT_18s0001g15390）实际上是由干旱胁迫诱导的。由于位于该区域 (chr17_10,497,222_C_T) 的 SNP 与气孔导度显着相关，因此通过对 85 个个体的基因重新测序，进一步研究了编码棉子糖合酶的 VIT_17s0000g08960 的遗传变异。我们的结果代表了在解析调节葡萄砧木缺水反应的遗传基础方面向前迈进了一步。从这项研究中获得的知识可能有助于在实际应用中利用基因型和表型多样性并协助进一步调查。