Research on substances involved in parasite-host communication

根寄生虫（如Orobanche和Striga）分布在地中海国家、中东和东非，对各种作物的生产造成巨大损害。这些寄生虫可以通过寄主作物根部分泌的种子萌发刺激物发芽，然后在附着于寄主根部之前通过寄主来源的刺激物再次产生吸器。这项研究的最终目的是保护农作物免受这些根寄生虫的侵害。为此，本研究试图阐明受寄主源性刺激物影响的小斑蝽种子萌发机制，以及寄主植物刺激物分泌与营养元素之间的关系。得到了以下三个结论。1)红三叶草根分泌三种化合物刺激小红三叶草种子。测定了这两种兴奋剂的结构。其中一个被鉴定出含有一种已知的兴奋剂，阿莱克醇。另一个是一个新的化合物，命名为orobanchl，并通过光谱和合成确定了其结构。2)发芽刺激物的分泌受营养元素的影响。硝酸盐对生产是必不可少的。然而，铵盐和磷酸盐抑制了兴奋剂的产生。钾对生产没有影响。3)寄主关系与萌发刺激物产生能力呈正相关。胡萝卜和红三叶草，这是已知的真正的宿主的小，可以产生高水平的兴奋剂。西红柿、大豆和豌豆，这些通常被认为会受到其他orobche物种攻击的物种，产生的活性与胡萝卜一样多。太阳花、黄瓜、洋葱、罗勒产生较弱的刺激活性，萝卜、芥和水稻产生微量或无刺激活性

Root parasites such as Orobanche and Striga species are distributed in the Mediterranean countries, Middle East, and East Africa and cause vast damages against production of various crops. These parasites can germinate by seed germination stimulants secreted by roots of host crops, then produce haustoria again by host-derived stimulants prior to attachment to host roots. The final aim of the study is to protect crops from these root parasite. To this end, we present tried to clarify seed germination mechanism of Orobanche minor as affected by host-derived stimulants as well as relationships between host plant stimulant secretion and nutritional elements. The following three conclusions were obtained.1) Red clover roots secrete three compounds to stimulate Orobanche minor seeds. The structures of the two of these stimulants were determined. One was identified with a known stimulant, alectrol. The other was a new compound named orobanchol and its structure was determined by spectroscopy and synthesis.2) Secretion of germination stimulants are affected by nutritional elements. Nitrate is essential for the production. However, stimulant production was suppressed by ammonium salts and phosphate. Potassium has no effect on the production.3) Positive relationships are present between hostship and germination stimulant producing ability. Carrot and red clover, which are known to be true host of Orobanche minor, can produced high levels of stimulants. Tomato, soybean and garden pea, which are generally known to be attacked other Orobanche species, produced as much activity as carrot did. Sun flower, cucumber, onion, basil produced weak stimulatory activity, while Raphanus, cress and rice secreted trace or no stimulatory activity