This study was conducted to investigate the antagonistic activity of endophytic and rhizosphere fungi isolated from a medicinal plant, Sesuvium portulacastrum, against Pythium aphanidermatum, the cause of damping off of cucumber. A total of 40 endophytic and 19 rhizosphere fungi were isolated from S. portulacastrum. Three endophytic isolates and two rhizosphere isolates gave >50% suppression of P. aphanidermatum in the in vitro dual-culture tests. Scanning electron microscopic studies at the inhibition zone showed hyphae wall damage and abnormal mycelial growth of the genus Pythium. Molecular analysis identified the antagonistic endophytes as Aspergillus insulicola (isolate A435), A. insulicola (A419), and Aspergillus melleus (A412) and the rhizosphere antagonists as Aspergillus terreus (A213) and Aspergillus luchuensis (A116). Except for A116, the culture filtrates of the other antagonists significantly increased the electrolyte leakage from Pythium mycelia, whereas ethyl acetate extracts of A435, A412, and A213 showed significant growth suppression. All five antagonists were able to produce varying amounts of cellulase and β-glucanase enzymes. However, A435, A412, and A213 showed significantly higher cellulase activity, whereas A435 and A116 showed the highest β-glucanase activity. Controlled glasshouse growth experiments showed that isolates A435 and A116 resulted in up to 70% control of damping off, whereas isolates A412 and A213 showed 30 to 40% damping-off control. The antagonists A435, A116, and A213 also contributed to increased cucumber shoot length as well as shoot and root dry mass. The synergetic effects of metabolites and hydrolytic enzymes could be the reason for the variation between isolates in the antagonistic activity and cucumber growth promotion. This study reports for the first time A. insulicola, A. melleus, and A. luchuensis as potential biocontrol agents against P. aphanidermatum-induced damping off of cucumber.Myrtle rust, caused by the pathogen Austropuccinia psidii, affects species of the Myrtaceae, many of which are endemic to Australia and New Zealand. Originating from South America, A. psidii is now present in both countries, necessitating effective chemical control for disease management. Using an artificial inoculation protocol, the efficacy of eight fungicides (tebuconazole/trifloxystrobin, cyproconazole/azoxystrobin, fosetyl aluminum, triforine, triadimenol, oxycarboxin, copper, and tebuconazole) applied as curative or protectant treatments was tested on two native New Zealand species (Lophomyrtus × ralphii and Metrosideros excelsa). The impacts of rate (×2), frequency (single or double), and timing (pre- or postinfection) of fungicide application were investigated. Overall, the most effective fungicides tested across both species were those that included a demethylation inhibitor and strobilurin mix, notably tebuconazole/trifloxystrobin (Scorpio) and cyproconazole/azoxystrobin (Amistar Xtra). These fungicides significantly reduced infection of host plants relative to the water control. Timing of application significantly affected bioefficacy, with applications made 7 days before inoculation or 7 days after inoculation being generally the most effective. The rate of fungicide application was not significant for both host species, with few interaction terms showing overall significance. Key findings from this study will set the foundation for further fungicide bioefficacy research conducted to evaluate formulations and adjuvant mixtures, determine suitable application methods for enhanced retention and coverage, and derive optimum application time for effective protection of native and exotic Myrtaceae species in New Zealand.Members of Fusarium graminearum species complex (FGSC) are the major pathogens that cause Fusarium head blight (FHB) in cereals worldwide. Symptoms of FHB on rice, including dark staining or browning of rice glumes, were recently observed in Jiangsu Province, China. To improve our understanding of the pathogens involved, 201 FGSC isolates were obtained from freshly harvested rice samples and identified by phylogenetic analyses. Among the 201 FGSC isolates, 196 were F. asiaticum and the remaining 5 were F. graminearum. Trichothecene chemotype and chemical analyses showed that 68.4% of the F. asiaticum isolates were the 3-acetyldeoxynivalenol (3ADON) chemotype and the remainder were the nivalenol (NIV) chemotype. All of the F. graminearum isolates were the 15-acetyldeoxynivalenol chemotype. Pathogenicity assays showed that both the 3ADON and NIV chemotypes of F. asiaticum could infect wheat and rice spikes. FHB severity and trichothecene toxin analysis revealed that F. asiaticum with the NIV chemotype was less aggressive than that with the 3ADON chemotype in wheat, while the NIV-producing strains were more virulent than the 3ADON-producing strains in rice. https://www.selleckchem.com/products/lgx818.html F. asiaticum isolates with different chemotypes did not show significant differences in mycelial growth, sporulation, conidial dimensions, or perithecial production. These findings would provide useful information for developing management strategies for the control of FHB in China.The soybean cyst nematode (SCN), Heterodera glycines, is the most damaging pathogen of soybean. Use of resistant cultivars is an effective strategy to manage SCN, but it also selects for virulent populations over time. A 12-year field experiment was initiated in 2003 to study how tillage and 11 different sequences of four cultivars impact SCN population dynamics and virulence. An SCN-susceptible cultivar and three resistant cultivars (R1, R2, and R3 derived from cultivars PI 88788, Peking, and PI 437654, respectively) were used. Tillage had minimal effect on SCN population density. Compared with no till, conventional tillage resulted in a faster increase of SCN virulence to Peking when the SCN was selected by R2 and virulence to PI 88788 by R3. Among the three SCN-resistant cultivars, R1 supported the greatest population density, R2 supported intermediate population density, and R3 supported the least SCN population density. The SCN populations selected by R1 overcame the resistance in PI 88788 but not in Peking and PI 437654.
This study was conducted to investigate the antagonistic activity of endophytic and rhizosphere fungi isolated from a medicinal plant, Sesuvium portulacastrum, against Pythium aphanidermatum, the cause of damping off of cucumber. A total of 40 endophytic and 19 rhizosphere fungi were isolated from S. portulacastrum. Three endophytic isolates and two rhizosphere isolates gave >50% suppression of P. aphanidermatum in the in vitro dual-culture tests. Scanning electron microscopic studies at the inhibition zone showed hyphae wall damage and abnormal mycelial growth of the genus Pythium. Molecular analysis identified the antagonistic endophytes as Aspergillus insulicola (isolate A435), A. insulicola (A419), and Aspergillus melleus (A412) and the rhizosphere antagonists as Aspergillus terreus (A213) and Aspergillus luchuensis (A116). Except for A116, the culture filtrates of the other antagonists significantly increased the electrolyte leakage from Pythium mycelia, whereas ethyl acetate extracts of A435, A412, and A213 showed significant growth suppression. All five antagonists were able to produce varying amounts of cellulase and β-glucanase enzymes. However, A435, A412, and A213 showed significantly higher cellulase activity, whereas A435 and A116 showed the highest β-glucanase activity. Controlled glasshouse growth experiments showed that isolates A435 and A116 resulted in up to 70% control of damping off, whereas isolates A412 and A213 showed 30 to 40% damping-off control. The antagonists A435, A116, and A213 also contributed to increased cucumber shoot length as well as shoot and root dry mass. The synergetic effects of metabolites and hydrolytic enzymes could be the reason for the variation between isolates in the antagonistic activity and cucumber growth promotion. This study reports for the first time A. insulicola, A. melleus, and A. luchuensis as potential biocontrol agents against P. aphanidermatum-induced damping off of cucumber.Myrtle rust, caused by the pathogen Austropuccinia psidii, affects species of the Myrtaceae, many of which are endemic to Australia and New Zealand. Originating from South America, A. psidii is now present in both countries, necessitating effective chemical control for disease management. Using an artificial inoculation protocol, the efficacy of eight fungicides (tebuconazole/trifloxystrobin, cyproconazole/azoxystrobin, fosetyl aluminum, triforine, triadimenol, oxycarboxin, copper, and tebuconazole) applied as curative or protectant treatments was tested on two native New Zealand species (Lophomyrtus × ralphii and Metrosideros excelsa). The impacts of rate (×2), frequency (single or double), and timing (pre- or postinfection) of fungicide application were investigated. Overall, the most effective fungicides tested across both species were those that included a demethylation inhibitor and strobilurin mix, notably tebuconazole/trifloxystrobin (Scorpio) and cyproconazole/azoxystrobin (Amistar Xtra). These fungicides significantly reduced infection of host plants relative to the water control. Timing of application significantly affected bioefficacy, with applications made 7 days before inoculation or 7 days after inoculation being generally the most effective. The rate of fungicide application was not significant for both host species, with few interaction terms showing overall significance. Key findings from this study will set the foundation for further fungicide bioefficacy research conducted to evaluate formulations and adjuvant mixtures, determine suitable application methods for enhanced retention and coverage, and derive optimum application time for effective protection of native and exotic Myrtaceae species in New Zealand.Members of Fusarium graminearum species complex (FGSC) are the major pathogens that cause Fusarium head blight (FHB) in cereals worldwide. Symptoms of FHB on rice, including dark staining or browning of rice glumes, were recently observed in Jiangsu Province, China. To improve our understanding of the pathogens involved, 201 FGSC isolates were obtained from freshly harvested rice samples and identified by phylogenetic analyses. Among the 201 FGSC isolates, 196 were F. asiaticum and the remaining 5 were F. graminearum. Trichothecene chemotype and chemical analyses showed that 68.4% of the F. asiaticum isolates were the 3-acetyldeoxynivalenol (3ADON) chemotype and the remainder were the nivalenol (NIV) chemotype. All of the F. graminearum isolates were the 15-acetyldeoxynivalenol chemotype. Pathogenicity assays showed that both the 3ADON and NIV chemotypes of F. asiaticum could infect wheat and rice spikes. FHB severity and trichothecene toxin analysis revealed that F. asiaticum with the NIV chemotype was less aggressive than that with the 3ADON chemotype in wheat, while the NIV-producing strains were more virulent than the 3ADON-producing strains in rice. https://www.selleckchem.com/products/lgx818.html F. asiaticum isolates with different chemotypes did not show significant differences in mycelial growth, sporulation, conidial dimensions, or perithecial production. These findings would provide useful information for developing management strategies for the control of FHB in China.The soybean cyst nematode (SCN), Heterodera glycines, is the most damaging pathogen of soybean. Use of resistant cultivars is an effective strategy to manage SCN, but it also selects for virulent populations over time. A 12-year field experiment was initiated in 2003 to study how tillage and 11 different sequences of four cultivars impact SCN population dynamics and virulence. An SCN-susceptible cultivar and three resistant cultivars (R1, R2, and R3 derived from cultivars PI 88788, Peking, and PI 437654, respectively) were used. Tillage had minimal effect on SCN population density. Compared with no till, conventional tillage resulted in a faster increase of SCN virulence to Peking when the SCN was selected by R2 and virulence to PI 88788 by R3. Among the three SCN-resistant cultivars, R1 supported the greatest population density, R2 supported intermediate population density, and R3 supported the least SCN population density. The SCN populations selected by R1 overcame the resistance in PI 88788 but not in Peking and PI 437654.
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