Dynamics of ascospore production in late autumn to develop better apple scab management strategies

一般认为，苹果黑星病菌的有性繁殖的年周期发生在冬季的落叶上，产生子囊孢子作为第二年春天的初级接种物。此外，随机交配赤霉病菌株相反的交配类型之间的假设。然而，我们最近表明，这种随机交配的假设是不支持的混合果园在过去十年中收集的数据。我们的数据表明，性交配更有可能发生和成功的分离物之间的病变在同一片叶子比接触独立感染的叶子落叶果园地板上。此外，我们的研究结果还表明，有性生殖很可能是在落叶之前开始的。如果这些都是真的，我们需要重新审视目前的共识/假设的赤霉病种群遗传学，特别是关于现有的真菌毒力因子的重组，使用混合果园的实用性，以及管理措施，以减少有性繁殖前落叶。这项建议将获得直接的证据来回答性行为是否在落叶前开始;是否在同一叶片上的病变之间更有可能成功进行性行为。然后，我们将开发和评估（主要是基于微生物的方法）控制措施来破坏有性生殖。最后，我们将使用NIAB EMR独特的结痂指示基因型集合（作为全球结痂毒力监测计划的一部分）来证明结痂毒力因子的重组是不可能的。这一结果对预测抗病基因的持久性、利用混合果园的可行性和减少初侵染量具有重要意义。

It is commonly assumed that the annual cycle of sexual reproduction of the apple scab fungus takes place on fallen leaves in the winter, producing ascospores as primary inoculum for the next spring. Furthermore, random mating among scab strains of opposite mating types is assumed. However, we recently showed that this random mating assumption is not supported by the data collected in a mixed orchard over the last ten years. Our data suggested that sexual mating is more likely to take place and succeed between isolates from lesions on the same leaf than contact between independently infected leaves in leaf litter on the orchard floor. Furthermore, our results also suggest that sexual reproduction is likely to be initiated before leaf-fall. If these are true, we need to re-visit current consensus/assumptions of scab population genetics, particularly regarding the recombination of existing fungal virulence factors, practicality of using mixed orchards, and management measures to reduce sexual reproduction before leaf-fall. This proposal will obtain direct evidence to answer Whether sex is initiated before leaf-fall;whether sex is more likely to succeed between lesions on the same leaves.Then, we will develop and evaluate (mostly microbial-based methods) control measures to disrupt sexual reproduction. Finally, we shall use the unique collection of scab indicator genotypes (as part of the global scab virulence monitoring programme) at NIAB EMR to demonstrate that recombination of scab virulence factors is unlikely. The results will have huge impact on predicting durability of resistance genes, feasibility of using mixed orchards, and reducing primary inoculum.