[Isolation, screening and identification of anantagonistic actinomycetes to control Fusarium wilt of Momordica charantia]. / é˜²æ²»è‹¦ç“œæž¯èŽç— çš„æ‹®æŠ—æ”¾çº¿èŒåˆ†ç¦»ç­›é€‰åŠé‰´å®š.

Fusarium oxysporum f. sp. momordica was used as the target pathogenic fungus to screen actinomycetes that were isolated from rhizosphere soil of Momordica charantia by confrontation culture and antifungal tests of fermentation filtrate. The candidate strain 0250 had broad antifungal activity. According to cultural characteristics, physiological and biochemical properties, as well as average nucleotide identity analysis of the strains with similar homology, the strain 0250 was identified as Streptomyces rhizosphaericus. Its effects on growth promotion and control of bitter gourd wilt were evaluated in both greenhouse and field. The results showed that the plate inhibition percentage of S. rhizosphaericus strain 0250 against F. oxysporum f. sp. momordica was 69.2%, while the plate inhibition percentage against 17 plant pathogenic fungi reached 64.3%-85.6%. The suspension treatment of the strain could promote the growth and development of roots and stems and improve production of bitter gourd in pots and field. The control efficacy of Fusarium wilt of bitter gourd was 66.9% and 61.5%, respectively. When soils were treated with the strain 0250 suspension in advance and inoculated with the fungal pathogen, the inhibition percentage on the soil F. oxysporum reached 62.1%. The activity of phenylalanine ammonia-lyase, peroxidase and ß-1,3-glucanase as well as root activity were significantly improved in bitter gourd seedlings. In summary, strain 0250 is an actinomycetes resource with biocontrol potential to Fusarium wilt of bitter gourd.

[Biocontrol potential of Talaromyces purpurogenus and its regulation on soil microbial community]. / äº§ç´«ç¯®çŠ¶èŒçš„ç”Ÿé˜²æ½œåŠ›åŠå ¶å¯¹åœŸå£¤å¾®ç”Ÿç‰©ç¾¤è½çš„è°ƒæŽ§.

Talaromyces purpurogenus strain Q2 is a kind of beneficial microbe originally separated from the rhizosphere of healthy cucumber. In this study, we evaluated the biocontrol potential of strain Q2 against four soil-borne diseases by plate confrontation culture, potting in the greenhouse. We further estimated the control efficacy of strain Q2 combined metam-sodium fumigation against Fusarium wilt of bitter gourd in the field. The mechanism of strain Q2 controlling bitter gourd wilt and regulating soil microbial community was examined by plate dilution culture, high throughput sequencing and quantitative PCR. The results showed that strain Q2 could efficiently reduce disease incidence of Fusarium wilt of bitter gourd, potato stem canker, black shank of tobacco and black root rot of tobacco in the green house. Its biocontrol efficacy on black shank of tobacco and bitter gourd wilt was 75.3% and 63.4%, respectively. Biocontrol efficacy of strain Q2 on bitter gourd wilt was 51.0% in the artificial disease nursery inoculated pathogen of bitter gourd wilt, while the control efficacy of strain Q2 combined with soil fumigation technology was more than 80% in the same experiment condition. Strain Q2 application and soil fumigation altered soil microbial community composition and recovery trend. Metam-sodium fumigation significantly reduced the abundances of Fusarium oxysporum and causal agent of bitter gourd wilt. Strain Q2 further suppressed the efficient recovery trend of the pathogen. After application of strain Q2, Penicillium was enriched in soil, as well as the beneficial microbes involved in the suppression of F. oxysporum, such as Bacillus and Gaiella. Overall, after soil fumigation, biocontrol efficacy of strain Q2 on soil-borne diseases such as Fusarium wilt could attribute to the formation of beneficial microbial communities in soil and inhibition of strain Q2 on growth and development of F. oxysporum.

[Genetic diversity and phylogenetic analysis of Fusarium oxysporium strains isolated from the Cucurbitaceae hosts revealed by SRAPs]. / ç“œç±»æž¯èŽç— èŒé—ä¼ å¤šæ ·æ€§å’Œäº²ç¼˜å ³ç³»çš„SRAP分析.

Cucurbitaceae wilt of different hosts could be caused by Fusarium oxysporum. To clear the genetic diversity and phylogenetic relationship of F. oxysporum isolates from different Cucurbitaceae hosts and regions, genomic DNA of ninety-five strains of F. oxysporum isolated from different hosts and different regions were amplified by sequence-related amplified polymorphism (SRAP) molecular markers. All strains could be uniquely distinguished with 238 polymorphism bands which generated 100% of polymorphic ratio with 19 selective primer pairs. On average, each primer pairs amplified 12.5 loci and 12.5 polymorphic loci. A total of 166 bands of F. oxysporum f. sp. momordicae (FOM) were amplified, among which 145 polymorphic bands generated 87.4% of polymorphic ratio. On average, each primer combination amplified 8.7 loci and 7.7 polymorphic loci. This indicated that genetic variation of F. oxysporum was extensive. The genetic similarity coefficient of F. oxysporum was 0.68-0.99, and the average indexes of Nei's genetic diversity and Shannon were 0.2390 and 0.3718, respectively. Ninety-five strains of F. oxysporum were divided into four formae speciales from bitter gourd, cucumber, watermelon and melon, when the genetic similarity coefficient was 0.74. In SRAP dendrogram all the FOM isolates were gathered into one phylogenetic branch with the genetic similarity coefficient ranging from 0.78 to 0.99. The average indexes of Nei's genetic diversity and Shannon indices were 0.1811 and 0.2750, respectively. This indicated that genetic diversity of FOM was abundant, and the classification of phylogenetic group was related to geographic origin to some extent.

[Systemic resistance induced by biocontrol agents in plants and its biochemical and cytological mechanisms].

Microbial biocontrol agents (BCAs) are generally used for controlling plant diseases via antagonistic mechanisms including competition, antibiosis, parasitism, and cross-protection. Some BCAs can even promote plant growth, and provide induced systemic resistance (ISR), i. e., induce the plants to have resistance against pathogens including phytopathogenic fungi, bacteria and virus, and in some cases, pest insects and nematodes. ISR is characterized by non-specific, wide spectrum and systemic. It is phenotypically similar to the systemic acquired resistance (SAR) induced by the infection of pathogens, and with the same efficiency but without hypersensitive response (HR) and visible symptoms in plant as SAR, which is helpful to open a new way to develop and improve safer and environmentally friendly strategies for plant protection. In this paper, the research advances on ISR mediated by biocontrol fungi and bacteria, elicitors or determinants, and signaling transduction pathways were summarized, with more emphasis on the biochemical and cytological mechanisms of host plant defense reaction induced by free-living and endophytic BCAs. The potential application of ISR in biocontrol of plant diseases was also discussed.