Unravelling the molecular genetic basis of Striga resistance in cereals: integrating Quantitative Trait Loci (QTL) and genomic approaches

大米和高粱是撒哈拉以南非洲(SSA)和半干旱热带地区数百万人的两大主食，但寄生杂草是制约作物产量和产量提高的主要因素。这种寄生虫附着在寄主植物的根上，造成严重的发育迟缓和粮食产量损失。目前，SSA 40%以上的谷物产区滋生了稻草；它们在贫瘠的土壤上影响最大，受影响最严重的是最贫穷的自给自足的农民，杂草对贫困和健康产生了重大影响。目前，减轻这种寄生虫影响的最常用策略包括人工除草、提高土壤肥力和使用“耐受”品种(即使在感染时也会产生一些谷物)，然而，成功的程度有限。虽然综合防治措施可能是控制稻瘟病菌的必要手段，但通过将寄主抗性基因导入最常用的品种，可以显著减少稻瘟病菌造成的作物损失。然而，由于缺乏抗性材料，以及对寄主对稻瘟病菌抗性的分子遗传性质缺乏了解，限制了抗病品种的使用。在过去的5年里，我们在水稻上开展了广泛的筛选计划，并鉴定了对S.hermonthica表现出良好的附着后抗性的品种。水稻对Striga抗性的发现具有重要意义，因为它是目前分子遗传学研究的最佳模式谷物，因为这种作物的基因组已经被测序。在这个项目中，我们建议采用一种综合的方法来鉴定和研究水稻对稻瘟病菌的抗性的分子遗传性质，结合我们对稻瘟病菌-寄主相互作用的广泛知识，我们的新植物生长系统以及现代基因组和比较基因组技术。然后，我们将使用从大米中获得的信息来确定高粱出现类似抗性的程度。该项目不仅将加强我们对稻瘟抗性分子遗传性质的基本了解，还将有助于开发更有效的稻瘟抗性育种方法，可用于非洲的区域和国家水稻和高粱改良育种计划。从长远来看，改良稳定产量的品种和自给自足的农民采用这些品种对于加强西非和撒哈拉以南非洲的粮食安全和减贫至关重要。

Rice and sorghum are two of the major staple foods for millions of people in sub Saharan Africa (SSA) and the semi-arid tropics yet a major constraint to crop production and yield improvement is the parasitic weed Striga. This parasite attaches to the roots of the host plant causing severe stunting and loss of grain yield. Currently Striga species infest over 40% of the cereal producing areas of SSA; their effects are greatest on infertile soils and those most severely affected are the poorest subsistence farmers upon whom the weed exerts major impacts on poverty and health. At present the most commonly used strategies for alleviating the impact of this parasite include hand weeding, improving soil fertility and the use of 'tolerant' cultivars (which produce some grain even when infected), however success has been limited. While combining several control measures is likely to be necessary for control of Striga, crop losses due to the parasite could be reduced significantly through introducing host resistance genes into the most commonly used cultivars. However, the use of resistant cultivars is limited by a lack of resistant material and by a lack of understanding of the molecular genetic nature of host resistance to Striga. Over the last 5 years we have carried out an extensive screening programme in rice and have identified cultivars that show good post-attachment resistance to S. hermonthica. The discovery of resistance in rice to Striga is of great significance as it is currently the best 'model' cereal for molecular genetic studies as the genome of this crop plant has been sequenced. In this programme we propose to take an integrative approach to identify and investigate the molecular genetic nature of resistance to Striga in rice by combining our extensive knowledge of Striga-host interactions, our novel plant growth systems and modern genomic and comparative genomic techniques. We will then use information gained from rice to determine the extent to which similar resistance occurs in sorghum. Not only will the project enhance our fundamental understanding of the molecular genetic nature of resistance to Striga but it will contribute to more efficient breeding methods for Striga resistance that could be used in regional and national breeding programmes in Africa for rice and sorghum improvement. The improvement of varieties which stabilize yields and their adoption by subsistence farmers is critical for enhanced food security and poverty reduction in West and sub Saharan Africa in the long term.