甘肃省白菜型冬油菜霜霉病发生规律

引起甘肃省白菜型冬油菜霜霉病的病原菌为十字花科寄生叉霜霉菌Peronospora parasitica（Pers.）Fr.,该病菌可为害叶片、茎秆和角果,病部出现白色霜状霉层。据调查,2009年-2011年间,油菜收获期霜霉病发病最严重,平均发病率和病情指数达32.80%和28.40。冬油菜霜霉病田间孢子囊4月上旬始见,5月22日左右达到高峰,平均为每100平方厘米71个;温度、相对湿度分别为16℃、95%时,接种72h后冬油菜霜霉病即可发生;当5d内平均温度为10.3℃、平均相对湿度为61.0%和5d内降雨量累计值为1.6mm时,田间孢子囊数目达最大,为每100平方厘米76个。陇油9号发病率和病情指数比其它品种显著高。小麦-冬油菜轮作可减轻霜霉病的发生。

Epidemics of downy mildew on winter turnip in fields of Gansu Province

The pathogen causing downy mildew of winter turnip in Gansu Province was identified as Peronospora parasitica（Pers.） Fr.It infected leaves,stem and pods of winter turnip and produced white mould on the surface of infected area.During 2009 to 2011,the average incidence and disease index reached 32.8% and 28.40 respectively at harvest stage.Pathogen sporangia were observed in early April in fields,and the quantity reached the top of the average density at 71 per 100 square centimeter in late May.At 16℃ with RH（relative humidity） 95%,the disease occurred 72h after inoculation.At 10.3℃ with RH 61.0% and 1.6mm rain precipitation in 5d,the sporangia density reached the highest of 76 per 100 square centimeter.Longyou 9 had significant high disease index and incidence than other cultivars.Wheat-winter turnip rotation could reduce the disease in field.