Study On The Pathogen And Control Techniques To Botrytis Cinerea On Rhododendron

Rhododendron is one of the ten most famous flowers with considerable economic values in our country,while the upgrowth and the worth for appreciation of cultivated rhododendron are fiercely damaged by grey mould on the petals and foliages.By microscopic characteristics of morphology and molecular identification,the separated pathogen was ascertained as Botrytis cinerea with over 99%homogeneity on rDNA-ITS sequence determination compared with Botrytinia fuckeliana in GenBank.For the mycelial growth of Botrytis cinerea,the optimum temperature was 22℃,and the optimum PH value was 5.The little acidity is suitable for its growth,but either the continuing light or the darkness has not significant effect on the mycelial growth.This pathogen has a distinct capability of utilizing various carbon source(monosaccharides,oligosaccharides and polysaccharides)with a best effect in glucose,later in fructose and sucrose.It also has a best utility in peptone,later in aspartic acid,and last in potassium nitrate among variety of nitrogen source.Five fungicides were screened for their toxicity to the pathogen of Rhododendron in laboratory.From the analyses of toxic regression equation and EC₅₀:50%chlorothalonil,75% chlorothalonil+thiram+ziram,80%carbendazim and 70%mancozeb have good but distinct restraining effect to this pathogen,with the EC50 153.05mg/L,4.47mg/L,40.70mg/L and 12.59mg/L respectively,while 70%thiophanate-methyl has not strong inhibition to the growth of mycelia.The higher the concentration is,the better the inhibition ratio will be up to.From the mechanism of antagonism on Botrytis cinerea by two antagonistic fungi(leaf-1 and stem-1),the inhibition ratio of leaf-1 is 79.7%higher than that of stem-1,which is 43.6%, after 5 days.The potted plant experiment of cultivation indicates that both spores and fermentation liquid of these antagonistic fungi possess certain functions of prevention and therapy to Botrytis cinerea.The effect of prevention is more significant than that of therapy.In therapy experiment,the application of spores and fermentation liquid of leaf-1 has an inhibition effect of 41.7%and 44.9%respectively after 15 days,while the effect of the treatment of stem-1 is 37.5%and 33.0%respectively.In prevention experiment,the application of spores and fermentation liquid of leaf-1 has an inhibition effect of 67.1%and 68.3% respectively after 15 days,while the effect of the treatment of stem-1 is 51.3%and 46.8% respectively.