OBJECTIVETo investigate diseases occurring in Rheum palmatum in Gansu province and identify pathogen.

METHODField survey in the main R. palmatum producing area and the pathogens were identified on the base of morphology.

RESULTEight fungal diseases have been found after disease surveys on R. palmatum in Gansu province from 2004 to 2007. They were leaf smut (Thecaphora schwarzmaniana), leaf spot (Septoria sp.), rust (Puccinia rheipalmati), ring spot (Ascochyta rhei), powdery mildew (Erysiphe polygoni.), grey mold (Botrytis sp.), root rot(Fusarium oxyxporium) and a virus disease.

CONCLUSIONLeaf smut, a severe disease with the incidence of 14%-26%, is the urgent problem waiting to be solved effectively. Powdery mildew and grey mold were reported for the first time in China.

Ascomycota ; pathogenicity ; Basidiomycota ; pathogenicity ; Botrytis ; pathogenicity ; China ; Fungi ; pathogenicity ; Fusarium ; pathogenicity ; Plant Diseases ; microbiology ; Rheum ; microbiology

Through investigation,it was found that the main disease of leaves was grey mold on Dendrobium officinale in Hubei province,which has a great impact on the yield and quality of D. officinale. The identification of morphological and molecular biological was used to prove that the pathogen was Botrytis cinerea. Through test the effect of 5 plant source fungicides and 4 antibiotic fungicides on mycelial growth of strain HS1,which proved 0. 3% eugenol had the best inhibitory effect,EC50 was 0. 29 mg·L^-1,the second was1% osthol and EC50 was 1. 12 mg·L^-1,the EC50 of 0. 5% matrine was 9. 16 mg·L^-1,the EC50 of the other six fungicides was higher than 10 mg·L^-1. The field control effect test proved that 0. 3% eugenol had the best control effect,reaching 89. 44%,secondly for 1%osthole,which was 77. 17%,0. 5% matrine was in the third place with 62. 37% of effective rate. However,the control effect of the other fungicides was less than 60%. The three plant-derived fungicides were safe for the produce of D. officinale and showed no phytotoxicity. The effect of these fungicides on the growth of D. candidum was tested,and proved that all the fungicides were safe and harmless to D. candidum. This study provides a research basis for the safe and effective prevention and control gray mold of D. officinale.
Alkaloids ; Botrytis/pathogenicity* ; Coumarins ; Dendrobium/microbiology* ; Eugenol ; Fungicides, Industrial ; Plant Diseases/prevention & control* ; Plant Leaves/microbiology* ; Quinolizines ; Matrines