向日葵霜霉病种子带菌研究

用种子洗涤检验法和分部染色检验法研究了向日葵霜霉病菌（Ｐｌａｓｍｏｐａｒａｈａｌｓｔｅｄｉ）种子带菌特点。结果表明，内果皮和种皮中带有菌丝体、吸器和卵孢子，胚和胚乳中不带菌，种子表面污染有孢子囊和卵孢子。另外，种子间混杂的病株残片也带有菌丝体、卵孢子和孢子囊。带菌种子传病试验证实带有卵孢子的种子能产生少数系统侵染病株；而仅带有菌丝体和吸器的种子，除萌发率降低，幼苗发育不良外，未发现任何症状，体内也未见病菌

Seed borne Nature of Plasmopara halstedii in Sunflower

The seed borne nature of Plasmopara halstedii in sunflower was studied by using diverse histopathological methods.Intercellular hyphae with haustoria and oospores were found in the pericarp and seed coat.No pathogen was seen in embryo and endosperm.Contaminated sporangia and oospores occurred on the surface of seeds.The small pieces of infected plant debris,mixed with living seeds,carried sporangia and oospores.The results of transmission experiments demonstrated that typical systemic infection was found in the plants grown from seeds with oospores.No symptoms developed in any of the plants grown from seeds with only mycelium and sporangia,which might reduce seed germination and seedling growth.