Investigation And Identification Of Fungal Diseases In Hainan Jackfruit,Three Fungal Pathogens Biological Characteristics And Fungicides Indoor Screening

Jackfruit(Artocarpus heterophyllus Lam.),whose English name is Jackfruit,is an important economic fruit in tropical regions of China.In recent years,due to the growing market demand,the production of jackfruit in Hainan has developed rapidly under the strong support of governments at all levels.From January 2017 to May 201 8,the fungal pathogen distribution and damage degree of jackfruit were investigated in Hainan,and the pathogen isolation and identification,biological characteristics and indoor virulence determination of Jackfruit Anthraenose,Fruit rot and Leaf spot were conducted.The results are as follows:1.Pathogen investigation of jackfruit fungal diseasesAnthracnose and fruit soft rot were the most serious fungal diseases of jackfruit in Hainan.Anthracnose occurred in jackfruit plantations in various cities and counties in Hainan,mainly affecting old leaves and fruits.The incidence ranged from 20%to 78%.Fruit and fruit soft rot occurred in all orchards.Fruit rot occurred in all orchards,the incidence of up to 40%;Fruit rot is more serious in Sanya and Baoting,among which the incidence of Nantian farm in Sanya is as high as 35%,and the incidence of male flowers in Baoting Xinxing farm is more than 80%.Leaf spot disease is very serious in Baoting and Danzhou.During the outbreak period,all the lower leaves of jackfruit are susceptible to the disease,especially in the annual outbreak in January.2.Study on anthracnose of jackfruitBased on the morphological characteristics of the pathogenic bacteria,combined with the polygenic phylogenetic analysis of ITS、GAPDH、ACT、CHS-1 and TUB2 sequences,the anthrax strain of Hainan jackfruit was identified for the first time as Colletotrichum siamense、Colletotrichum arxii and Colletotrichum pseudomajus.The biological characteristics of the most frequently isolated C.siamense were studied.the results showed that the pathogen on a PDA average growth rate of 1.38 cm/d,the optimal medium for jackfruit blade,decoct juice.medium mycelia killed 58℃ temperature for 10 min,the optimum growth temperature is 25-30℃,the optimum pH range of 6.0-9.0,soluble starch as the most ideal carbon source,yeast powder immersion and beef extract as the ideal nitrogen source,complete darkness most conducive to the growth of hypha.The indoor antibacterial effect of 13 fungicides on C.siamense was ranked from strong to weak as follows:20%Difenoconazole·Prochloraz>50%Prochloraz-manganese chloride complex>50%Carbendazim>50%Carbendazim·Mancozeb>300g/LDifenoconazole·Propic-onazole>250g/L Pyraclostrobin>10%Difenoconazol>50%Thiophanate-methyl>325 g/LDifenoconazole·Azoxystrobin>25%Bromothalonil>560 g/LAzoxystrobin·Chlorotha-lonil>400 g/L Pyrimethanil>500 g/L Iprodione.Among them,the EC50 value of 20%Difenoconazole Prochloraz was 0.0460 mg/L.3.Study on fruit rot of jackfruitBased on morphological characteristics,the phylogenetic analysis was established by combining the ITS sequence and EFl-a sequence of the pathogen and combining the two genes.The pathogen of jackfruit rot was identified as Lasiodiplodia theobromae.Jackfruit rot caused by L.theobromae was first discovered in China.The biological characteristics of L.theobromae were studied,and the results showed that:the pathogen on a PDA average growth rate of 3.03 cm/12 h,the optimal medium for jackfruit young fruit Fried juice medium and PSA medium,hyphae killed 53℃ temperature for 10 min,the optimum temperature range for 28-35℃,the optimum range of 5.0-8.0,fructose as one of the most ideal carbon source,followed by glucose,sucrose and galactose,yeast powder is the optimal nitrogen source,complete darkness most conducive to the growth of hypha.Choose 12 kinds of fungicides indoor antibacterial effect of the pathogen a from strong to weak order for:500 g/L Iprodione>50%Carbendazim.Mancozeb>50%Carbendazim>300 g/L Difenoconazole·Propiconazole>50%Thiophanatemethyl>20%Difenoconazole·Prochloraz>50%Prochloraz-manganese chloride complex>250 g/L Pyraclostrobin>10%Difenoconazole>400 g/L Pyrimethanil>325 g/L Difenoconazole Azoxystrobin>25%Bromothalonil.The EC50 value of 500 g/L Iprodione was 0.0880 mg/L.4.Study on leaf spot of jackfruitAccording to the morphological characteristics of the pathogen and ITS sequence based phylogenetic analysis,the leaf spot pathogens identified as Curvularia petersonii,caused by the bacterium jackfruit leaf spot was first discovered in China.The biological characteristics of C.petersonii were studied and the results showed that:Hyphae on a PDA average growth rate of 1.24 cm/d,the optimal culture medium for Fried juice medium and oat AGAR medium,Hyphae death 58℃ temperature for 10 min,the optimum growth temperature range for 28-35℃,the optimum pH range of 6.0-10.0,maltose and soluble starch as the ideal carbon source,peptone and beef extract,aspartic acid and yeast powder as the ideal nitrogen source,urea,ammonium sulfate,ammonium nitrate and sodium nitrate inhibit the growth of hypha,completely light the most conducive to the growth of hypha.Choose 11 kinds of fungicides indoor antibacterial effect of the pathogen from strong to weak order are:20%Difenoconazole·Prochloraz>50%Prochloraz-manganese chloride complex>300 g/L Difenoconazole·Propiconazole>250 g/L Pyraclostrobin>325 g/L Difenoconazole·Azoxystrobin>400 g/L Pyrimethanil>10%Difenoconazole>500 g/L Iprodione>560 g/L Azoxystrobin·Chlorothalonil>25%Bromothalonil>50%Carbendazim·Mancozeb.Among them,the EC50 value of 20%Difenoconazole·Prochloraz was 0.3918 mg/L.