Research on substances involved in parasite-host communication

点击翻译按钮获取中文摘要

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