| It is well known that Helianthaus annuus L.is an important oil crop and cash crop in the world.Verticillium wilt of sunflower is a typical soil-borne vascular bundle disease.Due to the lack of green,safe and effective prevention and control measures,this disease has seriously restricted the sustainable development of sunflower industry.Biological control is one of the important ways to solve soil-borne diseases such as sunflower verticillium wilt,which has a good development potential.Especially after the implementation of the national strategy of zero growth and reduced use of chemical pesticides,it has become a new development trend to create efficient,non-toxic and non-residual microbial pesticides for biological control of plant diseases.Biological control helps to promote the development of green,pollution-free and organic agriculture and accelerate the development of agricultural modernization.In this study,through screening and identification of sunflower verticillium dahliae biocontrol bacteria,we obtained the effective control of B.dahliae and the effect of increasing production on sunflower.The biological control strain and seed mixing agent were combined to screen out the preparation that can reduce the dosage of chemical agents and improve the control effect,so as to provide efficient control resources for the biological control of sunflower verticillium wilt in the future and provide a new control approach to improve the comprehensive control system of sunflower verticillium wilt.The main results are as follows:1.In this study,43 strains with antagonistic effect were isolated from the early stage,and 26 strains with inhibitory rate greater than 50% were obtained by plate antagonism and indoor bioassay.Field test was carried out on 26 antagonistic strains screened from laboratory.According to the comprehensive analysis of two field test sites in Hangjinhou Banner and Urat Front Banner of Bayannur,four strains with stable biocontrol effect and obvious yield increase were screened out.The control effect of root 7-3 was56.2%-58.5%,and the yield increase rate was 17.3%-24.9%.The control efficiency of strain 9-3 was 57.2%-59.3% and the yield increase was 15.9%-24.8%.The control efficiency of strain 7-4 was 55.9%-64.1% and the yield increase was 16.8%-26.7%.The control efficiency of L-S was 56.7%-65.8%,and the yield increase rate was16.1%-27.5%.2.Four biocontrol strains were identified according to the morphological characteristics,physiological and biochemical reactions of the bacteria and the nucleotide sequence analysis of 16 S r DNA.Strains L-S and root 9-3 were Bacillus velezensis.Root7-3 was Bacillus amyloliquefaciens.Root 7-4 was Bacillus subtilis.3.In order to improve the field control effect of biocontrol strains,the isolated biocontrol strains were mixed with the known biocontrol strains,and seeds were treated.The results showed that strain 7-4 combined with Trichoderma and strain L-S combined with Bacillus subtilis had the best control effect and the most obvious yield increase effect,with control effect of 70.4% ～ 74.6% and 71.5% ～ 74.5%,respectively.The yield was 261.6 kg/667 m2～266.69kg/667 m2 and 259.3 kg/～269.6 kg/667 m2,respectively,and the increase rates were 23.8% ～ 31.7% and 23.1% ～ 32.5%,respectively.4.Effects of biocontrol agents on the incidence and yield of sunflower verticillium wilt under different pesticide reduction conditions.The results showed that the biocontrol effect and yield increase of methyl topzine and fluoxonil combined with L-S were better than that of fluoxonil combined with root 7-3 and root 7-4 under the condition of 30%reduction.The biocontrol effect of fluoxonil combined with L-S was the best,with control effect of 63.9%-69.1%. |
