Enhancing resistance to existing and emerging insect pests of UK cereals

小麦是英国农业的主要作物，受到各种病虫害的侵袭。在英国，小麦的两种主要害虫是小麦球蝇和谷物蚜虫。小麦球茎蝇幼虫（蛴螬）在幼嫩植株的茎中挖洞，导致主要茎组织死亡，不能产生籽粒。谷物蚜虫从小麦的叶子和生长的谷物中吸取汁液，造成发育不良，还传播病毒性疾病，特别是大麦黄矮病毒（影响小麦、大麦和燕麦）。目前，小麦作物必须喷洒农药才能免受这些害虫的侵害；然而，由于对其他昆虫和整个生态系统产生影响，使用非特异性农药喷洒效率低、成本高，而且对环境不利。更糟糕的是，球蝇幼虫的破坏往往在农民意识到问题存在之前就已经发生了。气候变化的影响是平均气温上升，冬季变暖，这些害虫的袭击范围和严重程度都在扩大，甚至可能导致新的害虫将其活动范围扩展到英国。由于这些原因，从经济和环境的角度来看，开发小麦防虫的新方法越来越被视为优先事项。拟议的研究项目调查了开发新的作物保护方法的三种互补方法。首先，它观察了小麦植物受到谷类蚜虫和球茎蝇幼虫攻击时的反应。其中一些反应是由于植物组织受到任何损害而产生的，但其他反应则是特定于受到特定昆虫攻击的植物的。通过分析这些反应，我们将能够从小麦产生的具有杀虫活性的化合物以及小麦如何识别自己受到昆虫攻击的角度，确定小麦如何试图保护自己免受害虫的侵害。这种反应将与小麦植株的基因有关。然后，这些基因可以用于小麦育种计划，从而允许实施改善小麦防御反应的定向策略。其次，该计划调查了谷物蚜虫和小麦球茎蝇如何能够应对小麦植物使用的防御策略。由于小麦产生的化学物质，小麦对谷类蚜虫表现出部分抗性。然而，蚜虫能够忍受这些化学物质并存活下来。同样，小麦球茎蝇也能忍受植物的防御。通过研究昆虫是如何适应以小麦产生的物质为食来保护自己的，这些物质本来是杀虫的，可以设计出对抗昆虫适应的方法。这些措施可以采取喷雾的形式来阻止谷物蚜虫对小麦防御化学物质的耐受能力（这种化学物质对其他昆虫是特异性的，对环境无害的），或者采用一种策略来培育小麦，增加最有效地赋予抗性的化合物的数量，比如专门针对球蝇消化的抑制剂。第三，将两种新的杀虫化合物合成策略应用于该体系。一种策略是使用抗体来阻止昆虫肠道对糖或氨基酸的吸收；这种方法在对付另一种谷类作物害虫——稻褐飞虱方面已经取得了一些成功。第二种策略是使用可以由微生物或植物产生的新型蛋白质。这些新型蛋白质是两种独立的天然成分的融合，其中一种是杀虫毒素，另一种是与昆虫肠道结合的蛋白质。虽然单独喂食时两种成分都不杀虫，但融合蛋白被运送到昆虫循环系统，在那里它是活跃的。该计划的这一部分将导致新的环境友好型杀虫剂方法。

Wheat is a major crop in British agriculture, which is subject to attack by a variety of pests and diseases. Two of the major insect pests of wheat in the UK are wheat bulb fly and cereal aphids. Wheat bulb fly larvae (grubs) burrow in the stem of young plants, leading to death of the main stalk tissue, and failure to produce grain. Cereal aphids suck sap from the leaves and growing grains of wheat plants, causing stunting, and also transmit viral diseases, particularly barley yellow dwarf virus (which affects wheat, barley and oats). Currently, wheat crops have to be sprayed to protect them against these pests; however, spraying with pesticides which are not specific is inefficient, costly, and environmentally undesirable due to effects on other insects and throughout the ecosystem. Worse, damage by bulb fly larvae is often done before the farmer has realised the problem is present. Effects of climate change, which are increasing mean temperatures with warmer winters, are extending the range and severity of attacks by these insect pests, and may even result in new pests extending their range into the UK. For all these reasons, development of new methods for protecting wheat against insects are increasingly being regarded as a priority from economical and environmental viewpoints. The proposed research programme investigates three complementary approaches to developing new crop protection methods. First, it looks at the responses made by wheat plants when they are attacked by cereal aphids and bulb fly larvae. Some of these responses will be produced by any damage to the plant tissues, but others will be specific to plants attacked by a particular insect. By analysing these responses, we will be able to identify how wheat tries to defend itself against insect pests, both in terms of compounds wheat produces which have insecticidal activity, and in terms of how wheat recognises that it is under attack by an insect. The responses will be linked to genes in the wheat plant. These genes can then be used in wheat breeding programmes, to allow a directed strategy for improving wheat's defensive responses to be carried out. Secondly, the programme investigates how cereal aphids and wheat bulb fly are able to deal with the defensive strategies used by wheat plants. Wheat is known to exhibit partial resistance to cereal aphids, due to chemicals produced by the plants. Nevertheless, the aphids are able to tolerate these chemicals, and survive. Similarly, wheat bulb fly is able to tolerate plant defences. By studying how the insects are adapted to feeding on substances produced by wheat to defend itself, which are meant to be insecticidal, ways to counter the insect adaptation can be devised. These could take the form of a spray to block the cereal aphid's capacity to tolerate wheat defensive chemicals (which would be specific and environmentally non-damaging to other insects), or a strategy for breeding wheat with increased amounts of compounds which were most effective in conferring resistance, such as inhibitors specifically targetted towards bulb fly digestion. Thirdly, two novel strategies for producing insecticidal compounds are applied to this system. One strategy uses antibodies which block the uptake of sugars or amino acids from the insect gut; this approach has been tried with some success in another insect pest of cereal crops, the rice brown planthopper. The second strategy uses novel proteins which can be made by microorganisms, or in the plant. These novel proteins are a fusion of two separate naturally-occurring components, one of which is an insecticidal toxin, and the other is a protein that binds to the insect gut. While neither component is insecticidal when fed separately, the fusion protein is transported to the insect circulatory system, where it is active. This part of the programme will lead to new environmentally-friendly insecticide methods.