Screening Of Microbial Biocontrol Agents Against Cereal Cyst Nematode (Heterodera Avenae)

The effects of twenty Bacillus isolates were investigated in vitro on the motility of second stage juveniles of cereal cyst nematode Heterodera avenae.The isolate XZ33-3 showed significant results against juveniles(J2s)mortality followed by isolate XZ 17-1,isolate XZ 24-2-1,isolate MH 58-60-10,isolate MH 58-60-04 and isolate MH 01-04-01 simultaneously.Among them four Bacillus isolates were identified by molecular basis 16S rDNA,physiologically and biochemically carbon source utilization using API 50CHB strips and grouped as plant growth promoting bacteria(PGPR).In the green house experiments four identified isolates;B.cereus XZ 24-2-1,B.cereus XZ-33-3,B.weihenstephansis MH-58-60-01,B.thuringiensis MH 032-003,a nematicide(avermectin)were used as seed coating.All four Bacillus isolates significantly reduced nematode infection of wheat roots when juveniles were used as inoculum after 10 DPI.Noteworthy reduction in white female cyst development was observed on roots treated with avermectin seed coating followed by isolates B.cereus XZ 24-2-1,B.cereus XZ-33-3,B.weihenstephansis MH-58-60-01,B.thuringiensis MH 032-003 as compare to control treatment.In this study the bacterial isolates associated with Heterodera avenae cysts,wheat roots and wheat root rhizosphere from infested wheat field monoculture soil(?6y)were investigated.Bacterial strains were isolated by culture-dependent method,identified by gram's staining and screened against second stage juveniles(J2)mortality assay in vitro.About 15.0 percent of the total isolates showed 50.0%second stage juvenile(J2)mortality during initial 12 hour and was significantly increased up to70.0%by 35.5 percent of the total tested isolates after 24 hour duration.Molecular identification of five potential isolates performed by 16S rDNA,extracelluar metabolites detection for siderophores,hydrogen cyanide,proteaase and chitinase were detected.All five isolates were found Pseudomonasspp.and showed significant activity for secondary metabolites production.In green house experiment noteworthy reduction in white female development was observed as avermectin(77.18%)followed P.putida Ps Ps190(72.93%),P.putida Ps 197(66.67%),P.fluorescens Ps104(67.5%),P.putida Ps196(55.48%)and P.fluorescens Ps109(47.87)compare to untreated control treatment(P<0.05)however in field experiments significant reductions in white female cyst was observed on wheat roots before harvesting in different treatments as P.putida Ps196(68.64%)followed by P.putida Ps190(65.45%),P.putida Ps 197(64.94%),avermectin(64.44%),P.fluorescens Ps109(62.56%)and P.fluorescens Ps104(56.53%)compare to untreated control treatment(P<0.05).The seed bacterization also increased the wheat yields by Pseudomonas isolates as compare to untreated control(P<0.05).Alternatives to chemical pesticides mainly focused on biopesticides in crop protection and their commercialization includes Pseudomonas putida and P.fluorescence.These plant growth promoting rhizobacteria(PGPR)were effective in reducing different soil born root pathogens like cereal cyst nematode H.avenae.In this study we investigated different carbon and nitrogen sources in different type of media to optimize the fermentation and mass production of Pseuodomonas spp.Among all the media the suitable media composition containing carbon and nitrogen sources were found as media No.9,followed by No.10,No.08 and No.05 for the mass production of Pseudomonas spp.after 100 hours(4days).The secondary metabolites produced during fermentation in different media compositions showed varied results on the bioassay against the second stage mortality(J2)of H.avenae.The secondary metabolites formed in media No.8 and media No.5 has more toxic effects on the second stage juvenile(J2)mortality as compare to rest of secondary metabolites and control treatment.All tested strains of Pseudomonas spp.showed stability on pH ranges varied from acidic pH5 to neutral pH7 and towards basic pH8 against the second stage juvenile(J2)mortality assay.Many effective sources of resistance to CCN have been identified in cereals however their convenience and effectiveness is on the interaction of the specific putative resistant accession and the CCN pathotype found in a specific region.In this study 15 wheat lines from Zhongyuansun(CAAS)CIMMYT and 10 lines of oats from Jilin Province were screened against H.avenae.The results indicated that 5 wheat and 7 oats were ranked as resistance genotypes while 9 wheat and 3 oats were ranked as moderately resistant and 1 wheat line and the local check were highly susceptible to H.vaenae.These genotypes are needs to be exploited in breeding program to introduce the resistance gene in local cereal cultivars.The effect of biocontrol agents comprising Bacillus sp.and Streptomyces rubrogriseus on the management of the root-knot nematode were investigated alongwith a nematicide Fosthiazate on tomato susceptible cultivar Cv.Baiguoqiangfeng.The S.rubrogriseus culture filtrates(CF)showed maximum mortality of second stage juvenile(J2)followed by Bacillus sp.in first 12 hour exposure and after 24 hour duration of exposure time as compare to the control treatment containing medium(L.B).In the green house experiments Fosthiazate had significanlty increased the root length,shoot length and reduced number of root-knot nematode galls on tomato roots,followed by biocontrol agent S.rubrogriseus and Bacillus sp.as compare to the untreated control treatment after 60 DPI and 90 DPI.