Michel Vincent, Julio Emilie, Candresse Thierry, Cotucheau Julien, Decorps Christophe, Volpatti Roxane, Moury Benoît, Glais Laurent, Dorlhac de Borne François, Decroocq Véronique, German-Retana Sylvie
UMR 1332 Biologie du Fruit et Pathologie, INRA, Univ. Bordeaux, 71 Av. E. Bourlaux, CS 20032, 33882, Villenave d'Ornon Cedex, France.
Imperial Tobacco, La Tour, 24100, Bergerac, France.
Plant J. 2018 Jun 4. doi: 10.1111/tpj.13980.
Potato virus Y (PVY) is one of the most damaging viruses of tobacco. In particular, aggressive necrotic strains (PVY ) lead to considerable losses in yield. The main source of resistance against PVY is linked to the va locus. However, va-overcoming PVY isolates inducing necrotic symptoms were observed in several countries. In this context, it is important to find va-independent protection strategies. In a previous study, the phenotyping of 162 tobacco varieties revealed 10 accessions that do not carry the va allele and do not exhibit typical PVY -induced veinal necrosis. Despite the absence of necrotic symptoms, normal viral accumulation in these plants suggests a va-independent mechanism of tolerance to PVY -induced systemic veinal necrosis. Fine mapping of the genetic determinant(s) was performed in a segregating F2 population. The tolerance trait is inherited as a single recessive gene, and allelism tests demonstrated that eight of the 10 tolerant varieties carry the same determinant. Anchoring the linkage map to the tobacco genome physical map allowed the identification of a RPP8-like R gene, called NtTPN1 (for Nicotiana tabacum Tolerance to PVY-induced Necrosis1), with the same single-nucleotide polymorphism in the eight tolerant accessions. Functional assays using homozygous NtTPN1 EMS mutants confirmed the role of NtTPN1 in the tolerance phenotype. PVY -induced systemic veinal necrosis in tobacco likely represents an inefficient defense response with hypersensitive response-like characteristics. The identification of NtTPN1 opens breeding options to minimize the impact of emerging and so far uncontrolled va-breaking necrotic PVY isolates.
马铃薯Y病毒（PVY）是烟草最具危害性的病毒之一。特别是，具有侵袭性的坏死株系（PVY ）会导致产量大幅损失。抗PVY的主要抗性来源与va基因座有关。然而，在几个国家都观察到了能克服va抗性、诱导坏死症状的PVY分离株。在这种情况下，找到不依赖va的保护策略很重要。在之前的一项研究中，对162个烟草品种进行表型分析，发现有10个种质不携带va等位基因，也未表现出典型的PVY诱导的叶脉坏死。尽管没有坏死症状，但这些植株中病毒的正常积累表明存在一种不依赖va的机制来耐受PVY诱导的系统性叶脉坏死。在一个分离的F2群体中对遗传决定因素进行了精细定位。耐受性状作为一个单隐性基因遗传，等位性测试表明10个耐受品种中有8个携带相同的决定因素。将连锁图谱锚定到烟草基因组物理图谱上，使得能够鉴定出一个类似RPP8的R基因，称为NtTPN1（烟草对PVY诱导坏死的耐受性1），在8个耐受种质中具有相同的单核苷酸多态性。使用纯合NtTPN1 EMS突变体进行的功能分析证实了NtTPN1在耐受表型中的作用。PVY诱导的烟草系统性叶脉坏死可能代表了一种具有类似过敏反应特征的低效防御反应。NtTPN1的鉴定为育种提供了选择，以尽量减少新出现的、迄今无法控制的能突破va抗性的坏死PVY分离株的影响。
