Enhancing resistance to existing and emerging insect pests of UK cereals

小麦是英国农业的主要作物，容易受到各种病虫害的侵袭。在英国，小麦的两种主要害虫是麦球蝇和麦蚜。小麦鳞茎蝇幼虫(幼虫)在幼嫩植株的茎上挖洞，导致主要茎组织死亡，不能产生籽粒。麦蚜从小麦植株的叶片和生长的籽粒中吸取汁液，造成发育迟缓，还传播病毒病，特别是大麦黄矮病病毒(影响小麦、大麦和燕麦)。目前，小麦作物必须喷洒以保护它们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的影响，喷洒非特异性杀虫剂效率低、成本高，而且环境不受欢迎。更糟糕的是，球蝇幼虫造成的损害往往是在农民意识到问题存在之前造成的。气候变化的影响，随着冬季变暖而导致平均气温上升，扩大了这些害虫的攻击范围和严重程度，甚至可能导致新的害虫将其范围扩大到英国。出于这些原因，从经济和环境的角度来看，开发新的小麦防虫方法正日益被视为优先事项。拟议的研究方案调查了开发新的作物保护方法的三种补充办法。首先，它研究了小麦植株在受到谷类蚜虫和球果蝇幼虫攻击时的反应。其中一些反应将由植物组织的任何破坏产生，但另一些反应将针对被特定昆虫攻击的植物。通过分析这些反应，我们将能够确定小麦是如何试图防御害虫的，无论是从小麦产生的具有杀虫活性的化合物来看，还是从小麦如何识别自己受到昆虫攻击的角度来看。这些反应将与小麦植株中的基因联系起来。然后，这些基因可以用于小麦育种计划，从而实现改善小麦防御反应的定向策略。其次，该计划调查了谷类蚜虫和麦球蝇是如何应对小麦植株所采用的防御策略的。众所周知，小麦对谷类蚜虫表现出部分抗性，这是因为这种植物产生的化学物质。然而，蚜虫能够耐受这些化学物质，并存活下来。同样，小麦鳞茎蝇也能耐受植物的防御。通过研究昆虫如何适应以小麦产生的物质为食来自卫，这些物质本应是杀虫的，因此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，以阻止麦蚜耐受小麦防御性化学物质(这将是特定的，对其他昆虫无害的)，或者是一种策略，用增加化合物的数量来培育小麦，这些化合物在赋予抗性方面最有效，例如专门针对鳞茎蝇消化的抑制剂。第三，将两种新的生产杀虫化合物的策略应用于该系统。一种策略是使用抗体来阻止昆虫肠道中的糖或氨基酸的吸收；这种方法已经在另一种谷类作物的害虫--稻褐飞虱上进行了试验，并取得了一些成功。第二种策略使用可由微生物或在植物中制造的新型蛋白质。这些新的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。虽然单独喂养时这两种成分都不杀虫，但融合蛋白被输送到昆虫循环系统，在那里它是活跃的。该方案的这一部分将产生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.