| Plant parasitic nematodes have a dual role in pathogen. Tobacco parasitic nematodes can cause diseasecomplexes with avariety of pathogens. But there is little research on complex diseases in the domestic, and nematodes in roots are often ignored in prevention and treatment of root-disease. This test combined field investigation method and histopathology to analyze the role of Tobacco parasitic nematodesdiseases in the roots of tobacco; and with the help of PCR technique and themethod of morphological identification of Tobacco, kinds of Tobacco parasitic nematodes were identified; plot trail were taken to control the nematode andcomplex treatment in a four-year tobacco field, we screened out ecological preparations which can improve the soilhealth, control nematodes and fungal diseases in roots, and analyze the effect of different treatments on soil microbe diversity and enzyme activity.Major findings are as follows:(1)Combing themethod of field investigation and histopathology, Clarified the role of tobacco-parasiticnematodes in the roots disease and the prevalence of the combing nematode disease.According to the survey of 145 sample with roots disease in 12 county of Henan,11 counties (except Sheqi) exists the phenomenon of nematode complex infestation,and it accounted for 31.72% in total survey sample, about 40% tobacco roots diseasescaused by nematode complex infestation in Western Henan and 20% in centralHenan and Southern Henan. All evidence suggest that the complex infestation iscommonly and seriously in Henan,so it should be attached great importance.(2)Combing themethod of PCR technique and morphological identification, kinds of Tobacco parasiticnematodes were identified in Henan. Using degenerate primers TXF/TXR nematodesamples amplified DNA, we analyze 12 sample of tobacco nematode of 10 countyand there has Meloidogyne spp., Heterodera spp., Pratylenchus spp.and stem nematodegenus Ditylenchus spp.at least in Henan.At the same time,we found that primersTXF/TXR had highly specificity and sensitivityPerineal pattern-based morphological and PCR-based molecular identification revealed that 4 species of Meloidogyne occurred, of them M.incognita accounted for 57.08%, M.arenaria accounted for21.04%, M.hapla accounted for 18.96% and M.javanica accounted for 2.97%. This indicated that Meloidogyne incognita were the dominant population, other species in the pathogen population of tobacco root-knot nematode were increasing in Henan. All samples are mixed infection, M.incognita, M.arenaria and M.hapla were very common and widely distributed in Henan, while M.javanica distributed irregularly.Six cysts samples were collected from five counties (Mianchi,Yiyang, Dengfeng,Xuchang, Queshan)in Henan Province. The morphological characters of cyst were basically uniform and similar to those of soybean cyst nematode in the protruded vulval cone, ambifenestrate, well-developed underbridge and bullae. The vulval silt was (44.1 ±3.5) um long, the fenestra was (50.3±4.7) um long and (36.6 ±4.2) um wide. The underbridge was (83.6±4.8) um long and (11.1 ±0.9) um wide. Molecular identification was after wards carded out through duplex PCR with species specific primers. The results of morphological and molecular biological studies both indicated that the Tobacco-parasitizing cyst nematode was Heterodera glycines Ichinohe,1952.Four Pratylenchus spp. Samples from Ruyang, Dengfeng,Xuchang were amplificated by the specific primerss (18s-Int/26s-Int), all samples amplified out the 828 bp long target DNA fragment, showed that Ruyang, Dengfeng, Xuchang exist p. thornei.Xiangcheng county nematode sample was amplified by universal primer(rDNA1/rDNA2), and amplified out about 940 bp long target fragment, indicated that the Ditylenchus was Type A population of D. destructor(3) The control experiment was carried out In 4 years continuous cropping field, and analyzed the tobacco physiological character and soil microbial mass and soil enzyme activity, Select out two ecological elixirs(Story CX-10 & Story M-20) which mainly control the nematodes and also can control the black shank.The control experiment was carried out In Yiyang county.After the drug treatment, we investigate the incidence in 30d and 90d,at the same time, recovery hazard situation of nematode and the occurrence of tobacco black shank at the final phase of tobacco,then calculate the control effect according to the root knot index and disease index. The survey conduct of three times indicated that the period of preserving effect of Avermectins is the shortest,the control effects of avermectins continued declining and the index were between 26.71% and 51.63%, but the control effects of Fosthiazate is increased significantly and following decreased significantly,the index were between 61.92% and 79.35%.In contrast, Plant nematocide, Story CX-10 and Story M-20 is the longest, the control effects of the Story M-20 were between 72.25% and 75.46%, the Plant nematocide were between 74.18% and 76.42% and the Story CX-10 were between 78.16% and 80.53%,among them, Story M-20 and Story CX-10 can observably decline the disease index of tobacco black shank and the average relatively control effect is above 65%,so the two of them can control tobacco black shank in the meanwhileThe results of soil microbial conventional separation showed that:CX-10 and M-20 have intenseactivation function on soil bacteria and actinomycetes and have a stronginhibitory effect against fungi. The number of soil bacteria after processing with CX-1033.19% increase 33.19%, actinomycetes increase 50.74%and fungidecrease 51.8%. This regulatory role of microbial flora is very helpful to restoresoil health. The measured results of soil enzyme activity also support thisconclusion. CX - 10 have intense activation function on soil Invertase, amylaseand cellulase, the soil enzyme activity increased by 63.85%,43.47% and 50%respectively after processing. Dolly M 20 can strongly activated soilinvertase and amylase, but it had strong inhibitory effect on cellulose enzyme.Three kinds of soil enzyme activity changes were+ 111.24%,+75.42% and -111.24% respectivelyThe above resultsshow that the application of ecological preparations not only can improve soilenzyme activity and soil microbial diversity, recovery soil health and hassignificant effect on Nematode disease and other root diseases, it also helps earlyonset of tobacco and improve the resistance of tobacco, it is worthy offurther development and application. |
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