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

尽管油菜（OSR; Brassica napus）传统上被认为是最赚钱的间作作物，但白菜茎虱（CSFB; Psylliodes chrysocephala）的失控导致英国的种植面积在2012年至2019年期间下降了35%。全国农民联盟（NFU）估计，取消新烟碱类种子处理每年使农民损失约9400万英镑的机会和作物损失。由于需要进口OSR，英国破碎行业已经吸收了额外的成本。总的来说，这对英国OSR产业的生存能力和当前的农作物轮作做法构成了严重的风险。随着化学防治的退出，抗性品种是支持害虫综合治理（IPM）战略的核心。然而，与植物-病原体相互作用不同，我们对寄主植物和咀嚼昆虫之间相互作用的理解是有限的。芥子油甙是芸苔属植物用来阻止非专业害虫的化学物质。即使甘蓝型油菜有防御或抗性机制阻止CSFB的取食，这种机制的遗传控制以及它们是否可以被利用来培育抗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的抗性实例，对英国作物品种的抗性机制也知之甚少。目前尚无抗OSR害虫的品种。该建议建立在使用控制饲养研究和现场试验的初步数据的基础上，这些数据表明，在不同的甘蓝型芽孢杆菌群体中，成虫CSFB饲养减少的变化存在。该小组包括冬季和春季OSR，中国OSR，瑞典和羽衣甘蓝的历史品种，包含不太可能在精英品种中出现的遗传多样性。这使我们能够确定与CSFB摄食损伤相关的位点。在该种群中进行的控制幼虫侵染研究也发现了CSFB成虫的数量变化，表明对CSFB幼虫存在抗性。总之，这些观察结果表明，某些品种的甘蓝型油菜携带的基因可以1)阻止成虫对CSFB的摄食，2)赋予抵抗幼虫侵染或降低幼虫繁殖力的能力。如果确定，可以利用这种变异来培育OSR，以抵抗CSFB的两个破坏性阶段。该提案由两个研究机构（JIC和Rothamsted research）、七个主要的植物育种机构和OSR种植者征税委员会（AHDB）共同提出，旨在发现与甘蓝型油菜成虫CSFB摄食和幼虫抗性相关的位点。与此同时，我们的目标是了解影响OSR-CSFB相互作用的作物适应性。这将与幼虫发育研究、基因表达分析和代谢物分析相结合，进一步阐明芸苔属植物识别和防御甲虫攻击的关键机制。与抗性和防御反应相关的关键基因将通过模式植物的候选基因研究进行研究，包括支持数据中涉及的两个基因座的候选基因。总的来说，这些知识与参与育种者将使用的种质和标记相结合，将抗性等位基因整合到商业育种管道中，将有助于将耐受性品种引入英国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.