EAGER: An Unexplored Avenue of Striga Resistance in Maize

斯特里加菌是一种寄生植物，它以玉米、高粱、旱稻、小米和豇豆的根部为食，对撒哈拉以南非洲和发展中国家其他地区依赖这些作物的人们的生活造成严重破坏。联合国粮食及农业组织（粮农组织）指出，虽然玉米是非洲所有大田作物中面积最大的，但其平均产量（1.6吨/公顷）还不到世界其他地区单位面积产量的三分之一。Striga种子与玉米籽粒和玉米穗混在一起进入市场，使情况进一步恶化。这个EAGER项目将利用新发现的转座子诱导的（非转基因）玉米突变体来测试一种潜在的新策略，用于处理Striga侵染。这种植物携带一种编码类胡萝卜素裂解双加氧酶8 （ccd8）的基因突变，并已被证明产生很少或不产生独角麦内酯（SL）的前体，独角麦内酯是一种玉米激素，被寄生真菌感知，是寄主定位和种子发芽所需的化学信号。这种新的玉米突变体的非转基因性质也增加了它被不同文化的民族接受和使用的前景。这个项目将测试玉米和孤角麦内酯之间的实际相互作用在多大程度上受到了对植物生物学中孤角麦内酯部分理解的作用的影响。具体目标是：1)确定ccd8突变对斯特riga种子萌发和寄主吸引的抗性程度；2)通过基于杂交活力和自然发生的遗传调节剂的育种策略，验证ccd8玉米在不丧失斯特riga抗性的情况下可以抵消相对适度的产量损失的概念。如果取得成功，该EAGER项目将提供一种新的战略，可以应对由斯特里加菌造成的15%至100%的产量损失，从而使斯特里加菌侵染地区的玉米生产具有可持续性。

Striga is a parasitic plant that feasts through the roots of corn, sorghum, upland rice, millet, and cowpea, devastating these crops and the lives of people who depend on them in sub-Saharan Africa and other areas in the developing world. The Food and Agriculture Organization of the United Nations (FAO) notes that, while maize has the largest acreage of all field crops in Africa, the average yield (1.6 t/hectare) is less than 1/3 of that achieved per unit area elsewhere in the world. The situation is further exacerbated by widespread dispersal of Striga seeds that intermix with maize kernels and ears going to market. This EAGER project will test a potentially novel strategy for dealing with Striga infestation using a newly identified transposon-induced (non-transgenic) mutant of maize. This plant carries a mutation in a gene that encodes a carotenoid cleavage dioxygenase 8 (ccd8) and has been shown to produce little to no precursors for strigolactone (SL), a maize hormone that is sensed by the Striga parasite and is required as a chemo-signal for host location and germination of its own seeds. The non-transgenic nature of this new maize mutant also enhances prospects for its acceptance and use by peoples with diverse cultures. This project will test the extent to which actual interactions between maize and Striga are affected by the partially-understood roles of strigolactone in plant biology. The specific objectives are to: 1) determine the degree of resistance to Striga seed germination and host attraction offered by the ccd8 mutation, and 2) test the concept that a relatively modest yield penalty in ccd8 maize can be countered without losing Striga resistance, by breeding strategies based on hybrid vigor and naturally-occurring genetic modifiers. If successful, this EAGER project will provide for a new strategy that could counter Striga-based yield losses that extend from 15% to 100%, thereby making maize production sustainable in Striga infested regions.