Next generation apple breeding for resilient UK production

获得新的苹果品种对英国苹果业未来的可持续性至关重要，因为新品种往往具有明显更高的零售价值，因此为苹果种植者提供了更大的利润。然而，许多引入英国市场的新品种对苹果黑星病(_Venturia Equalis_)、白粉病(_Podosphaera Leucotricha_)和欧洲溃烂病(_Neonectria Ditissima_)都很敏感，这三种病害在英国非常流行。这导致对白粉病和赤霉病的单基因抗性被很好地记录下来，抗赤霉病基因Rvi6的使用已经成功地纳入了世界各地的育种计划。相比之下，记录在案的对欧洲溃烂病的抗性是多基因的，在苹果育种中应用不佳。因此，在商业品种中，缺乏对这三种病害具有联合抗性的品种，并且严重依赖单一的抗赤霉病基因。培育抗性提高的苹果是一个漫长的过程，传统上需要20-25年。这样的时间尺度使苹果业容易受到新的生物和非生物威胁的出现以及有效植物保护产品的可获得性的影响。该项目旨在开发现代育种方法，以缩短苹果的育种周期，并确保新的、更具抗性的品种更快地进入市场。该项目将研究三种育种方法及其缩短育种周期的潜力：基因组选择、分子标记-性状关联和快速育种。基因组选择是一种利用覆盖整个基因组的标记进行选择的标记辅助选择形式。这种育种方法使动植物育种发生了革命性的变化，对高度多基因的性状特别有用。然而，基因组选择在苹果育种中还没有得到广泛的应用，也没有关于它作为苹果多基因抗病选择工具的有效性的报道。在这个项目中，我们将评估基因组预测模型对欧洲溃烂病的抗性，这是英国生产的一个基本特征。快速育种是一种通过操纵环境生长条件来加速植物发育的工具，从而允许快速的世代循环。这种方法与基于标记的选择方法相结合，具有很大的潜力，可以在显著缩短的时间框架内培育出满足工业和消费者需求的多抗性苹果品种。我们将利用光周期、植物激素和生长调节剂的组合来调控苹果的植株发育和种子休眠。

Access to new apple varieties is crucial for the future sustainability of the UK apple industry, as new varieties tend to have a significantly higher retail value and therefore offer larger margins for apple growers. However, many of the new cultivars introduced to the UK market are susceptible to apple scab (_Venturia inequalis_), powdery mildew (_Podosphaera leucotricha_) or European canker (_Neonectria ditissima_), three apple diseases that are highly prevalent in the UK. This has led to a heavy reliance on chemical disease control.Monogenic resistance to powdery mildew and scab are well-documented and the use of the scab resistance gene _Rvi6_ has successfully been incorporated in breeding programmes worldwide. In contrast, the documented resistances to European canker are polygenic and have been poorly deployed in apple breeding. There is thus a lack of cultivars with combined resistance to all three diseases and a heavy reliance on a single resistance gene against scab in commercial cultivars. Breeding apples with improved resistance is a long process, traditionally taking 20-25 years. Such timescales leaves the apple industry vulnerable to the emergence of new biotic and abiotic threats and to the availability of effective plant protection products.This project aims to develop modern breeding methods to enable a shorter breeding cycle of apple and ensure a faster route to market for new, more resistant cultivars. The project will research three breeding methods and their potential to shorten the breeding cycle: genomic selection, molecular marker-trait associations and speed breeding.Genomic selection is a form of marker-assisted selection in which markers covering the whole genome are utilised for selection. This breeding method has revolutionised animal and plant breeding and is particularly useful for highly polygenic traits. Nevertheless, genomic selection has not been widely adopted in apple breeding and there are no reports of it's efficacy as a selection tool for polygenic disease resistance in apple. Within this project we will evaluate genomic prediction models for resistance to European canker, an essential trait for UK production.Speed breeding is a tool in which environmental growth conditions are manipulated to accelerate plant development, thereby allowing for rapid generation cycling. Integrated with marker-based selection methods, this methodology has great potential to produce multi-resistant apple cultivars which meet industry and consumer demand in a significantly reduced time-frame. We will use a combination of photoperiod regime, plant hormones and growth regulators to manipulate the plant development and seed dormancy in apple.