BR2CSFB - A toolkit for breeding resistance to adult and larval herbivory by the cabbage stem flea beetle

尽管油菜(OSR；Brassica napus)传统上是最有利可图的休耕作物，但由于失去了对甘蓝茎跳甲(CSFB；Junlliodes chryocephala)的控制，导致英国的种植面积在2012至2019年间下降了35%。全国农民联盟(NFU)估计，取消新烟碱种子处理使农民每年损失约9400万GB的机会和作物损失。由于需要进口OSR，额外的成本已被英国压榨行业吸收。总体而言，这对英国OSR行业的生存能力和当前的农作物轮作做法构成了严重风险。随着化学防治措施的取消，抗病品种成为支持害虫综合管理(IPM)战略的核心。然而，与植物-病原菌的相互作用不同，我们对寄主植物和咀嚼昆虫之间的相互作用的了解是有限的。CSFBs被硫代葡萄糖苷吸引，硫代葡萄糖苷是油菜物种用来阻止非专业害虫的化学物质。即使甘蓝型油菜具有阻止CSFB取食的防御或抗性机制，这种机制的遗传控制以及它们是否可以被利用来繁殖抗药性仍然是一个悬而未决的问题。目前还没有已知的甘蓝型油菜抗性实例，对我们英国作物物种内的抗性机制知之甚少。目前还没有对油菜害虫具有抗性的品种。这项建议建立在采用控制取食研究和田间试验的初步数据的基础上，这些数据表明，在不同的甘蓝型油菜群体中存在减少成虫取食量的变异。该小组由冬春OSR、中国OSR、瑞典和羽衣甘蓝等历史品种组成，包含精英品种不太可能存在的遗传多样性。这使得我们能够确定与CSFB取食损害相关的基因座。在该种群内的受控幼虫侵染研究还发现，羽化的CSFB成虫数量发生了变化，表明存在对CSFB幼虫的抗性。总之，这些观察结果表明，一些油菜品种携带的基因可以1)阻止成虫取食，2)提高对幼虫侵染的抗性或降低幼虫的繁殖力。如果确定，这种变异可以被利用来培育对CSFB的两个危害阶段都具有抗性的OSR。这项建议由两个研究机构(JIC和Rothamsted Research)、七个主要植物育种者和OSR种植者委员会(AHDB)提出，旨在发现与甘蓝型油菜成虫取食和幼虫抗性相关的基因座。同时，我们的目标是发展对影响OSR-CSFB相互作用的作物适应的理解。这将与幼虫发育研究、基因表达分析和代谢物图谱相结合，进一步阐明十字花科植物识别和防御甲虫攻击的关键机制。在模式植物中，将利用候选基因研究来研究与抗性和防御反应有关的关键基因，包括支持数据中涉及的两个基因座下的候选基因。总而言之，这些知识与种质和标记相结合，将被参与育种的人用来将抗性等位基因整合到商业育种管道中，将有助于将耐受品种引入英国OSR市场。

Although oilseed rape (OSR; Brassica napus) has traditionally been grown as the most profitable break crop, a loss of controls for cabbage stem flea beetle (CSFB; Psylliodes chrysocephala), has resulted in UK cropping area declining by 35% between 2012 and 2019. The National Farmers Union (NFU) estimate the removal of neonicotinoid seed treatments has cost farmers ~£94 million/year in lost opportunity and crop loss. Additional costs have been absorbed by the UK crushing industry because of the need to import OSR. Collectively, this poses a serious risk to the viability of the UK OSR industry and current farm crop rotation practices. With the withdrawal of chemical controls, resistant cultivars are central to supporting Integrated Pest Management (IPM) strategies. However, unlike plant-pathogen interactions, our understanding of the interactions between host plants and chewing insects is limited. CSFBs are attracted to glucosinolates, chemicals used by Brassica species to deter non-specialist insect pests. Even if B. napus has defence or resistance mechanisms that deter CSFB feeding, the genetic control of such mechanisms and whether they can be exploited to breed for resistance has remained an open question. There are no known examples of resistance in B. napus and little knowledge of resistance mechanisms within our UK crop species. No resistant cultivars are currently available for any insect pest of OSR.This proposal builds on preliminary data using controlled feeding studies and field trials, which shows that variation for reduced adult CSFB feeding is present within a diverse panel of B. napus. The panel, comprising historical varieties of winter and spring OSR, Chinese OSR, swede and kale, contains genetic diversity which is unlikely to be present in elite cultivars. This has enabled us to identify loci associated with CSFB feeding damage. Controlled larval infestation studies within this population have also identified variation in the numbers of emerging adult CSFB, demonstrating the presence of resistance to CSFB larvae. Together these observations indicate that some varieties of B. napus carry genes which can 1) deter adult CSFB feeding and 2) confer resistance against larval infestation or reduce larval fecundity. If identified, this variation can be exploited to breed OSR resistant to both damaging stages of CSFB. This proposal developed by two research institutes (JIC and Rothamsted Research), seven major plant breeders and the OSR growers' Levy board (AHDB), aims to discover loci associated with adult CSFB feeding and larval resistance in B. napus. In parallel, we aim to develop an understanding of crop adaptations which affect OSR-CSFB interactions. This will be coupled with larval development studies, gene expression analysis and metabolite profiling to further elucidate key mechanisms by which Brassica plants identify and defend themselves against beetle attack. Key genes implicated in resistance and defence responses will be investigated using candidate gene studies in model plants, including candidate genes which underlie two loci implicated in the supporting data. Collectively, this knowledge, combined with germplasm and markers that will be used by participating breeders to integrate resistant alleles into commercial breeding pipelines, will facilitate the introduction of tolerant varieties into the UK OSR market.