| Tobacco is a kind of important economic crop all over the world, and the tobacco root-knot nematode is one of the most dangerous pests in most tobacco planting areas. It occurred, widely distributed and seriously damaged the tobacco planting in most of province all over our country. For the resistance of planting varieties to tobacco root-knot nematode is low, most people still keeps taking chemical pesticide as the main way to control this disease. Thus, it causes the drug-resistant development, environmental pollution, and the exceeded heavy metals contents in tobacco leaves, and so on, finally impacts the disease control effect, ecological safety and mankind health. In this research, trials for searching biological control of tobacco root-knot nematode disease were designed, mainly for screening antagonistic strains, evaluation of inhibition in greenhouse and exploring the impacts on growth and development of tobacco root-knot nematode which was bought by antagonistic strains. And the purpose of this research is to establish a feasible system to screening antagonistic strains and take biological control of tobacco root-knot nematode.1. The preliminary screening of antagonistic strains against Meloidogyne incognita45isolated laboratory strains have been screened by Meloidogyne incognita. Preliminary screening,28.9percent of total number of test strains were screened out, showed that13strains had antagonistic effcet on Meloidogyne incognita,14strains of which were fungi and8strains of which were bacteria.3of them caused more than70percent mortality of the second stage juveniles. Respectively, they were the fungus Trichoderma harzianum strain YZL229, the bacteria Pseudomonas fluorescens strain P-72-10and Bacillus subtilis strain Itb162.2. Ovicidal and larvicidal effect of strain YZL229, P-72-10and Itb162on M. incognita in vitroStrain YZL229, P-72-10and Itb162, whose effects were known in the process of the preliminary screening, were used to test their ovicidal and larvicidal effect on M. incognita. The results showed that, all treatments displayed nematicidal potentials through ovicidal and larvicidal assays in vitro. The egg hatch inhibitory effect of the strains’supernatants when treated for48h from big to small was YZL229>P-72-10>Itb162. We found that strain YZL229had the best egg hatch inhibitory effect, and the effect of strain Itb162was low among three strains of them, but they were all significantly different from the control. And the same situation was occurred in the larvicidal effect test of three strains. The mortality of the second stage juveniles which treated by strain YZL229were higher as94.7%, and that of strain Itb162were lower as62.3%. But they all had significant difference when compared with control. In addition, the parasitic test on eggs of M. incognita by strain YZL229showed the parasitic rates of eggs were high as73.4%which treated for7days. And during the test, we also found that strain YZL229prefer to parasite on mature eggs rather than young eggs.3. Evaluation of resistance to tobacco root-knot nematode disease in greenhouseThe nematicidal potential of three native biological agents containing the fungus Trichoderma harzianum strain YZL229, the bacteria Pseudomonas fluorescens strain P-72-10and Bacillus subtilis strain Itb162which collected from Meloidogyne spp. infested tobacco fields and infected roots in Chongqing, against the root-knot nematode, Meloidogyne incognita, infecting tobacco, was assessed in vitro and under greenhouse. All treatments displayed nematicidal potentials through ovicidal and larvicidal assays in vitro and resulted in significant improvement in tobacco growth in greenhouse. The significant suppression of gall index (GI) and eggmass index (EMI), the reduction of nematode population in rhizosphere soil and eggs per eggmass were obviously observed following the application of these biocontrol agents, especially Trichoderma harzianum strain YZL229. Generally, the results of this study indicated that the tested biological agents could prove to play a significant role in integrated root-knot nematode management on tobaccos.4. Penetration and post-infection development of Meloidogyne incognita as affect by strain P-72-10The bio-control potential of rhizospere bacterium Pseudomonas fluorescens against plant-parasite nematode has been demonstrated. P. fluorescens has been shown to enhance tobacco resistance to the root-knot nematode Meloidogyne incognita. Inoculation of tobacco with P. fluorescens could lead to significant reductions in the number of juveniles that penetrated tobacco root and further life stage development of the juveniles. The number of juveniles penetrated tobacco root in treatment with P. fluorescens was significantly different from CK at2DAI,6DAI,8DAI and10DAI. Significant reduction and delayed development of the number of juveniles that penetrated tobacco root and treated with P. fluorescens was observed at14DAI,21DAI,28DAI and35DAI. In addition, P. fluorescens treatment led to a significant reduction in the number of eggs per egg-mass at35DAI. The results show P. fluorescens induced a continuously suppression on root-knot nematode M. incognita throughout their entire early infection phase of root penetration, subsequent life stage development and their reproduction.5. Establishment of technology system of resistance to tobacco root-knot nematode in resources of antagonisticThis study used three strains after a preliminary screening to teste their ovicidal and larvicidal effects on M. incognita in vitro, to evaluate their disease control effects to tobacco root-knot nematode disease in greenhouse and to affect penetration and post-infection development of Meloidogyne incognita. From three different angles fully verified the inhibitory action and bio-control potential of three strains against tobacco root knot nematodes, set up a systematic and feasible screening technology system of resistance to tobacco root-knot nematode inresources of antagonistic. In the ovicidal and larvicidal test, we did the parastic test to the eggs and second stage juveniles using the fungi which may able to have the parasitic ability on the eggs and second stage juveniles, at the same time we did the ovicidal and larvicidal test using three strains’supernatants also, and three strains inhibition effect was fully verified; in the disease control in greenhouse pot experiment, GI, EMI and amount of unit soil nematodes were investigated, fully verified bio-control effect of three strains; in the eperiments of effect of penetration and post-infection development of Meloidogyne incognita, The results show P. fluorescens induced a continuously suppression on root-knot nematode M. incognita throughout their entire early infection phase of root penetration, subsequent life stage development and their reproduction. Based on the above results in three aspects, this study established a systematic and feasible system of resistance to tobacco root-knot nematode in resources of antagonistic, aims to verify biocontrol potential to provide effective technical means. |
PDF Full Text Request