Suppression Effects Of Wuyiencin On Tea Foliar Diseases And Their Pathogens

Wuyiencin is an agricultural antibiotic with extensive inhibitive effect,which was obtained from the culture filtrate of Streptornyces ahygroscopicus vat.wuyiensis. Wuyiencin exhibits strong effects on many pathogenic fungi of crops.However,it has not been tested to control diseases on tea crops.Investigations were conducted to study the effects of wuyiencin on suppression of the pathogens of tea leaf blight (Colietotrichum camelliae)and gray blight(Pestalotiopsis theae)in the laboratory and to examine its efficacy to control tea foliar diseases in the field.1.The pathogen caused brown blight on tea was isolated in Jinyun mountain of Chongqing,Based on its pathogenesis test,morphological and biological characteristics, the pathogen was identified as Colletotrichum camelliae(teleomorph:Guignardia camelliae).This pathogen could grow on different culture media and PSA was the most suitable medium for growth and sporulation of the fungus.The mycelium grew best under 25℃temperature with 5-8 pH value.Hypha lost viability when temperature was increased to 65℃for 15 min.2.Tea leaf blight caused by C.camelliae is one of the most widespread and important diseases on tea crops.In this study,the effects of wuyiencin(a mycofungicide produced from the fungus Streptomyces ahygroscopicus var.wuyiensis)on the growth, sporulation and infectivity of the pathogen G.camelliae were examined,After the conidia were treated with wuyiencin,the germination rates of the spores were significantly lowered;the hyphae from the germinated spores became malformed and hyphal growth was seriously hindered.On PDA plate containing different concentrations(8.3-25.0 mg/l)of wuyiencin,the growths of the pathogen colonies were severely inhibited and efficacy of inhibition was positively and linearly correlated with the concentrations of the fungicide.After the pathogen was cultivated with PD medium (PDA without agar)for seven days,the relative electro-conductivity of the culture liquid was increased significantly(P＜0.05).This implied that the fungicide interrupted the structure and function(i.e.osmosis)of haphal cell membranes of the pathogenic fungus.3.Pot-grown tea plants were treated with 12.5mg/L wuyiencin to examine its effect on amount or activity of photosynthetic pigment,soluable sugars(WSS), malondialdehyde(MDA),peroxidase(POD)and superoxide dismutase(SOD)in lea leaves.The results showed that wuyiencin could increase the contents of chlarophy A and B,WSS,and the activity of SOD and POD,but decrease the amount of MDA.It may be concluded from these resulta that wuyiencin application can induce resistance to tea diseases,to promote plant growth and delay senescence of tea leaves.4.Adisease survey was performed on tea crops in 9 counties of Chongqing,China and 16 leaf diseases were diagnosed and recorded.These tea diseases were leaf blight (Collectortichum cameliae),gray blight(Pestalotiopsis theae),sooty blight (Neocapnodium theae),lichinosis(Parmelia cetrata,Barbella pendula,Drummondia sinensis,etc.),anthracnose(Colletotrichum theae-sinensis),white scab(Elsinoe leucospila),Phyllosticta leaf spot(Phyllosticta theae),Gray mold(Botrytis cinerea), alga red rust(Cephaleuros virescens),red leaf spot(Phoma theicola),root-knot nematode(Meloidogyne spp.),bud blight(Phyllosticeta gemmiphliae),sclerotial blight (Sclerotium rolfsii),blister blight(Exobasidium vexans),shoot withering(Diplodia theae-sinensis)and copper blight(Guignardia camelliae).The first four were the commonest diseases present;the distribution frequency and prevalence of the four diseases reached over 70%and 30%,respectively.The leaf blight and gray blight were the most damaging diseases in tea orchards of these counties.A field experiment was conducted to test the efficiency of wuyiencin in controlling tea diseases.Recordings in the experimental tea fields before wuyiencin sprays showed that the percentages of diseased leaves(PDLs)of leaf blight,gray blight and other leaf spot diseases were 38.42%,13.53%and 54.82%,disease severities(DSs)were 8.65%, 5.74%and 7.44%,respectively.Two sprays with wuyiencin(concentration 16.7mg/L and dosage 25 L/667 m~2)were applied twice on June 18 and July 2,2006.The intensities of leaf diseases were recorded 18 days following the last spray.In the treated plots,the PDLs were 12.81%,6.12%and 10.37%,and the DSs were 5.27%,1.96%and 2.07%,respectively for the three kinds of diseases;but in the CK plots the PLDs were increased to 44.68%,17.68%and 84.84%,the DSs to 13.52%,8.55%and 9.86%, respectively.Based on PLD and DS data in the CK crops,the relative efficiencies of leaf diseases control by wuyiencin were 61.02%-87.78%.Statistic analysis showed that these disease control effects were all extremely significant(P＜0.001).However, analysis also showed that the disease control achieved by wyjiencin was not significantly different from that by standard fungicide carbendazim(P＞0.05).This result indicates that wuyiencin can be applied to replace carbendazim in controlling leaf diseases in tea fields.