Does apple canker develop independently on leaf scars of a single apple shoot?
Does apple canker develop independently on leaf scars of a single apple shoot?
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DOI：
10.30843/nzpp.2021.74.11739
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发表时间：
2021
影响因子：
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通讯作者：
Xiang-ming Xu;L. Olivieri;A. Gange;L. Vorster;Don Rice;R. Campbell;M. Walter
中科院分区：
文献类型：
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作者：
Xiang-ming Xu;L. Olivieri;A. Gange;L. Vorster;Don Rice;R. Campbell;M. Walter
由迪蒂新赤壳菌（Neonectria ditissima）引起的欧洲苹果溃疡病对苹果树，尤其是幼树造成严重损害。由于有效杀菌剂有限、潜伏期长、接种体数量多、商业品种的寄主抗性以及需要昂贵的人工修剪干预措施，溃疡病的防治很困难。为了了解病害聚集情况以便更有效地进行修剪管理，我们评估了在同一枝条上，叶痕处的溃疡病感染以及随后病斑的发展是否相互独立。进行了四项接种实验：一项在温室中，三项在果园里。在每个枝条上，对连续的10个叶痕进行接种，并随时间在原地对可见溃疡病进行评估。对每个枝条上形成的溃疡病数量以及这些溃疡病在枝条内的空间分布进行了统计分析。单枝上可见溃疡病斑数量的大多数数据不符合二项分布（独立性的指标），而用贝塔二项分布拟合要好得多。在一些情况下（4 - 20%），相邻叶痕上病斑的发展之间似乎存在正相关。然而，在一项实验中，对接种但无症状的叶痕（经过8个月的田间培养）进行实验室培养和迪蒂新赤壳菌的分离，结果表明单枝上溃疡病的发展是独立的。我们得出结论，单枝上溃疡病斑的明显聚集很可能源于寄主的反应。在田间病害评估和管理中，应考虑单枝上溃疡病斑的这种聚集情况。
European apple canker, caused by Neonectria ditissima, causes serious damage to apple trees, particularly young trees. Canker management is difficult because of the limited availability of effective fungicides, the long latency period, inoculum abundance and host resistance in commercial cultivars as well as the need for costly manual pruning interventions. To understand disease aggregation for more effective pruning management, we assessed whether canker infection and subsequent lesion development on leaf scars are independent from each other on the same shoot. Four inoculation experiments were conducted: one in glasshouse, and three in orchards. On each shoot, 10 consecutive leaf scars were inoculated and assessed for visible cankers over time in situ. Number of cankers developed per shoot as well as spatial distribution of these cankers within a shoot was statistically analysed. Most data of the number of visible canker lesions on a single shoot failed to fit binomial distributions (indicator for independence) and were fitted much better by beta binomial distributions. In a number of cases (4–20%), there appeared to be positive association between lesion development on neighbouring leaf scars. However, in one experiment where laboratory incubation and isolation of N. ditissima from inoculated but asymptomatic leaf scars (after eight months’ field incubation) were used the results suggested independence of canker development on a single shoot. We conclude that apparent aggregation of canker lesions on individual shoots is likely to originate from host responses. Such aggregation of canker lesions on individual shoots should be taken into consideration for field disease assessment and management.