Studies On Occurrence, Yield Loss And Control Of Clubroot On Rapeseed Caused By Plasmodiophora Brassicae

The occurrence and damage of rape clubroot disease caused by plasmodiophora brassicae had been aggravating in Hubei province in recent years. This disease has a serious influence on rape yield and quality, which becomes one of the major diseases to the production of rapeseed. Hence, understanding the occurrence and harmful of rape clubroot disease, selecting disease-resistant varieties and effective chemical control methods have a significant impact on the control of the occurrence and damage in rape clubroot disease as well as the integrated control of clubroot disease in field.The study of the occurrence dynamics and its effect on the growth and yield of rape clubroot disease in Dangyang, Hubei province during2012-2013, and the result showed that the whole growth periods of rape can be infected by plasmodiophora brassicae, mainly in seeding stage. One month after sowing, the obvious swelling can be observed in the roots of rape seedlings in direct seeding; then a slightly higher incidence was showed in late November to early January; after entering over-wintering stage the incidence of rape was flattened out; the disease incidence soared in the following March; then reached a peak on April22, until the harvest. The disease occurred in the transplanting rape until March, and then reached a peak on April22. Compared with direct seeding, the occurrence of clubroot disease was slow and lighter in transplanting rape. The clubroot in the seeding age had no obvious effect on plant growth in different disease levels; after grey moss stage, the plant height and growth rate appeared difference in different disease levels; to the maturation stag, the rapeseed presented a significant difference in plant height in different disease level. After infected by P. brassicae, the effective branch numbers of rapeseed, effective pod numbers per plant, and seed number per pod and1000-grain weight were significantly decreased to the health rapeseed. Compare with the direct seeding of rape, the transplanting rape showed a lighter disease and smaller yield lose in rapeseed.The resistance of49rapeseed varieties to clubroot disease was evaluated under greenhouse and field conditions, the result showed that there were1high resistance variety and7resistance varieties under greenhouse condition. There was only yanyou2showed high resistances in the whole growing period under field condition, and it was in accordance with the result under greenhouse condition. Therefore, this variety could serve as germplasm resources to resistant the rape clubroot disease in Hubei province.5kinds of fungicides were chosen to test their indoor toxicity by using spores germination rate inhibition method. The result showed that the best inhibition effect of spore germination was Cyazofamid. The precedence ordering of inhibiting capacity of5kinds of fungicides on resting spores germination was Cyazofamid>Fluazinam> Chlorothalonil>Carbendazol>Cymoxanil-Mancozeb. The indoor pot test showed the disease index of Cyazofamid was the lowest in different applying time, and the best applying time was5days after inoculating. The field experiment showed the disease index of Cyazofamid was the lowest in different applying time, and the best applying time was applying the fungicides2days before inoculating. The results on field experiment and indoor pot test were basically the same; and as a kind of effective chemicals, the Cyazofamid could be used to control the clubroot disease in the field.