曲靖烤烟根部病害发生规律及防治菌剂筛选OA

[Objective]The study aimed to clarify the epidemic patterns,identify the pathogens,and screen for biocontrol bacteria and fungi-cides of root rot in flue-cured tobacco in Qujing city,Yunnan province,and further provide theoretical basis and technical support for the sci-entific control of this disease.[Method]Systematic surveys were conducted on the incidence of root diseases in flue-cured tobacco during its growth stages across four representative tobacco-growing areas in Qujing city.Pathogens were identified through morphological observation combined with multi-gene phylogenetic analysis using ITS,β-tubulin,EF-1α,and RPB2.The effects of different culture media,temperature,pH,and light conditions on the growth and sporulation of the identified pathogen were studied.Antagonistic biocontrol bacteria were isolated and screened from soil,and their pot trial efficacy was assessed.The field efficacy of fungicides such as 35 g/L azaconazole·fluxapyroxad and 687.5 g/L fluopyram·propamocarb against root rot and black shank was evaluated through independent regression analysis of indoor vir-ulence testing and comparison of disease index in field experiments.[Result]In Qujing's tobacco-growing areas,root rot symptoms first ap-peared during the bunching stage and progressively worsened as the growth period progressed.The severity of the disease among the four rep-resentative tobacco-growing areas ranked as follows:Jiuxian town in Malong county,Yuezhou town in Qilin distict,Reshui town in Xuanwei county,and Lashan town in Luoping county.Yunyan 87 was highly susceptible to root rot,while K326 exhibited resistance,Yunyan 100 and Yunyan 105 showed moderate resistance.The pathogen was identified as Fusarium solani through morphological observation combined with multi-gene phylogenetic analysis.At 28 ℃,the growth rate of F.solani on oat agar and carrot agar medium was significantly higher than those on the other five types of media.Sporulation was significantly higher on carrot agar medium and Gauze's synthetic broth medium compared to the other five types.At 30 ℃ on potato dextrose medium,both growth rate and sporulation reached their highest levels.The growth rate peaked at pH 12,while sporulation was the highest at pH 8.Light had no significant effect on the growth of the pathogen but significantly promoted sporulation.From 60 bacterial isolates,five antagonistic strains were selected and identified as Bacillus velezensis through 16S rDNA sequence phylogenetic analysis.Among them,LSJ-1 achieved a pot trial efficacy of 82.15％and significantly improved the agronomic traits of tobacco seedlings.The combination of 35 g/L azaconazole·fluxapyroxad and 687.5 g/L fluopyram·propamocarb demonstrated a field efficacy of 81.78％against root rot and black shank.[Conclusion]The pathogen of root rot in flue-cured tobacco in Qujing city was identified as F.so-lani.It was recommended to prioritize the use of the disease-resistant variety K326 in production,and to implement a combined control strate-gy using the antagonistic agent LSJ-1 along with the chemical compound combination of fludioxonil·mefenoxam+fluazinam·propamocarb from the transplanting to rosetting stages.