Two weedy parasites are known in potato: Orobanche spp. (O. ramose, O. aegyptiaca and O. cernua) parasitize potato roots, and Cuscuta spp. (mainly C. campestris) parasitize potato shoots. Orobanche spp. is an important pest of many crops in Mediterranean countries in the Middle East and in Africa, extending eastwards to central Asia, India, China, and southern Russia, and northward to Central and Eastern Europe. Orobanche seeds are 0.2-0.3 mm long, and can remain viable in soil for decades, waiting for appropriate germination conditions. These include a few days under suitable temperatures and humidity, and a chemical stimulus from host roots. After germination, the parasite attaches to root surface, and develops a haustorium that penetrates host root tissues. The haustorium serves as a physiological bridge that directly connects the parasite to the vascular systems of its host, allowing the uptake of water, nutrients, and assimilates. After initial connection to potato roots the parasite can alsoconnect to potato tubers.
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