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Orobanche aegyptiaca
''Orobanche aegyptiaca'', Egyptian broomrape, is a plant which is an obligate holoparasite from the family Orobanchaceae with a complex life cycle. This parasite is most common in the Middle East and has a wide host range including many economically important crops.
Selective control of Egyptian broomrape is extremely difficult because the close association between host crop and parasite limits the use of most mechanical and herbicidal approaches.
== Disease Cycle ==
A single Egyptian broomrape plant is capable of producing hundreds of thousands of extremely small (0.15-0.5 mm long) seeds. These seeds, dispersed by the wind, animals, or by more artificial means such as farm machinery, survive in the soil and have the ability to remain viable in the soil for more than 15 years. When the seeds are dropped, they are dormant. They require after-ripening, or further ripening after the seed has fallen from the plant, which is completed by the time the dry season has ended. As the rainy season begins, the seeds imbibe water and move into a conditioning phase which lasts 1–3 weeks, depending on whether the temperature remains optimal, between 60 and 70 degrees Fahrenheit. At this point, the seeds only need a chemical signal from the roots of a host plant to germinate. The seeds can remain in this conditioned state for several months. If the seed never receives the chemical signal to germinate and dries out, it will return to its dormant state, ready to be re-conditioned when the next rainy season begins.〔Reference 2.〕
When a conditioned seed receives a chemical signal from a host plant, it germinates, forming a germ tube which grows toward the host. From this germ tube, it grows a haustorium. The haustorium is the part of the broomrape which attaches the parasite to the host and grows into the host’s vascular system. The parasite is then able to draw out water and nutrients from its host.〔Reference 3.〕 At this point, ''O. aegyptiaca'' grows rapidly, developing above-ground flower stalks. The flowers develop between February through May.〔Reference 6.〕 A medium-sized plant can produce more than 400 flowers, which each produce around 500 seeds. The complete life cycle of this parasite, if completed in one season, lasts 10 to 15 weeks.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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