Molecular Detection Of Primary Infection Pathogen Causing Fruit Shrinking Disease In Zizyphus Jujuba Mill. And Its Control

In this study, the total DNA of jujube tissues was amplified using two specific primerpairs. It was proved that Alternaria alternata was the pathogen causing fruit shrinkingdisease and had obvious latent infection. Fungal pathogenic strains of jujube fruit shrinkingdisease (JFS) were inoculated into the field fruit with spaying, stabbing and unstabbing.And the diseased fruits were similar to the natural JFS symptoms. The same strains wereobtained by isolating the inoculated and infected tissues. Nine fungicides and two bacterialagents were applied for the control of jujube fruit shrink disease. The agentia which hascertain control effect was screened, in order to provide a theoretical basis for effectivecontrol of jujube fruit shrinking disease.In this study, the total DNA of subhealthy fruits and diseased fruits from differentregions, fruits in different diseased stage and the same region, and different organs of thesame tree were amplified using two specific primer pairs, AAF2/AAR3and Aalt-F/Aalt-Rfor Alternaria alternata. Water and healthy fruits were used as negative controls, while thepathogen strain CN194of jujube fruit shrinking disease and diseased fruit were served aspositive controls. Pathogen of jujube fruit shrinking disease was detected by agarose gelelectrophoresis. The specific fragments of341bp and450bp were amplified from theDNA template of diseased fruits from diseased regions, but not from the healthy fruits inthe region without shrinking disease. The two specific fragments were amplified as well insubhealthy fruit, flower and young fruit from regions with disease symptoms over the lastyears, but not in leaf and hanging of jujube tree from diseased region. It was demonstratedthat A. alternata mainly infects flowers and young fruits with obvious latent infection infruits.Five A. alternata strains causing primary infection of jujube fruits, which wereobtained from Tang county and Xingtang county, Hebei Province, Panzhuang town inPuyang city, Xuedian town in Xinzheng city and Houhe town in Neihuang county, HenanProvince, were inoculated into the Zizyphus jujuba Mill. cv. Pozao fruit in Xingtang county,Hebei Province, the Z. jujuba Mill. cv. Huizao fruit in Xinzheng city, Henan Province andthe Z. jujuba Mill. cv. Bianhesuanzao fruit in Panzhuang town, Henan Province by surfacestabbing of fruit. The symptoms of the inoculated jujube fruit were similar to natural ones of jujube fruit disease. The same strains were obtained by isolating the issues of inoculatedand infected jujube fruits. And it was confirmed that the inocula were the initial infectedpathogens of jujube fruit shrink disease with Koch’s postulates. And the pathogen ofdifferent varieties of Zizyphus jujuba was identical. The inoculated jujube fruits became illin natural contidions. Spraying flowers with spore suspension could result in infection ofjujube fruits, in which the symptom was similar to the natural ones. Stabbed inoculationshould be carried out in the slow growth period. There might be climate reason which caninhibit the growth of pathogen in the jujube fruits because the infected tissue around thewounds were very limited in expanding period and white maturity period.The in vitro inhibition to spore germination and mycelium growth of nine fungicidesagainst pathogen were tested by germinating the fungal spore on concave slides andgrowing inhibition of mycelium on PDA agar plates. And the inhibition to sporegermination of two bacteria was tested by germinating the fungal spore on concave slides.The results indicated that nine fungicides could significantly inhibit spore germinating andmycelium growth, whereas Guofukang showed the highest inhibition rates, reaching90.8%and77.2%. And the bacterial Y2and Y4could significantly inhibit the mycelium growth.The control rate of carbendazim was42.5%. One bacterial agent, Y2，showed significantcontrol effect in the late, with control rate of92.6%compared with the control. The controlresults in the field indicated that the control effect was28.9%, respectively, by sprayingiprodione with1000dilution times. The control effect of mancozeb, thiram, mixture ofcarbendazim and Guofukang, guofukang carbendazim, ethylicin, Wuyiencin andcarbendazim is not effective enough. Prochloraz did not reduce the incidence of disease infield application, but even increased the disease severity. It is probably that somepharmaceutical ingredients in this fungicide can promote the growrt of A. alternata.