Beauveria bassiana myco-insecticides/acaricides are usually formulated as conidia infection suspensions (CIS) in sterile distilled water plus 0.1% tween 80 (v/v) for field and laboratory applications. However, stress factors i.e., temperature, UV radiation, oxygenation, can over time compromise the conidial viability and virulence. The native strain of B. bassiana has been shown to be highly virulent against the poultry red mite Dermanyssus gallinae. With the aim of investigating the best storage conditions for extending the CIS shelf-life, viability and virulence of native B. bassiana CIS stored at ambient and refrigerated temperatures (i.e., 20±1 °C and 4±1 °C, respectively), with and without light and agitation, were assessed over a one year period. The viability of conidia was assessed monthly by quantitative plate counts of colony forming units (CFU)/ml on potato dextrose agar after incubation at 25°C for 4 days. The virulence of B. bassiana was evaluated towards D. gallinae five times in one year (i.e., at T0 and every 3 months of storage). Independently of light conditions and agitation, all CIS stored at 20±1 °C showed a reduction of about two logarithmic units of CFU/ml, starting from the 2nd month, which persisted until the 12th incubation month. CIS stored at 4±1°C showed a reduction of about one logarithmic unit of CFU/ml starting from the 7th month and remained unchanged until the end of the monitoring time. The highest mortality rate of D. gallinae was registered for CIS stored at 4±1°C, in the dark and without agitation. This study suggests that the viability of the spores during storage is only dependent on temperature, whereas the virulence of the fungus is influenced by temperature, light and agitation. Refrigerating CIS (i.e., 4±1 °C), with storage in the dark and without agitation seems to guarantee the best viability and performance against D. gallinae, thus it can be considered the most appropriate storage method.
Influence of different storage conditions on the viability and virulence of Beauveria bassiana conidia infection suspension
GIANGASPERO, ANNUNZIATA;
2016-01-01
Abstract
Beauveria bassiana myco-insecticides/acaricides are usually formulated as conidia infection suspensions (CIS) in sterile distilled water plus 0.1% tween 80 (v/v) for field and laboratory applications. However, stress factors i.e., temperature, UV radiation, oxygenation, can over time compromise the conidial viability and virulence. The native strain of B. bassiana has been shown to be highly virulent against the poultry red mite Dermanyssus gallinae. With the aim of investigating the best storage conditions for extending the CIS shelf-life, viability and virulence of native B. bassiana CIS stored at ambient and refrigerated temperatures (i.e., 20±1 °C and 4±1 °C, respectively), with and without light and agitation, were assessed over a one year period. The viability of conidia was assessed monthly by quantitative plate counts of colony forming units (CFU)/ml on potato dextrose agar after incubation at 25°C for 4 days. The virulence of B. bassiana was evaluated towards D. gallinae five times in one year (i.e., at T0 and every 3 months of storage). Independently of light conditions and agitation, all CIS stored at 20±1 °C showed a reduction of about two logarithmic units of CFU/ml, starting from the 2nd month, which persisted until the 12th incubation month. CIS stored at 4±1°C showed a reduction of about one logarithmic unit of CFU/ml starting from the 7th month and remained unchanged until the end of the monitoring time. The highest mortality rate of D. gallinae was registered for CIS stored at 4±1°C, in the dark and without agitation. This study suggests that the viability of the spores during storage is only dependent on temperature, whereas the virulence of the fungus is influenced by temperature, light and agitation. Refrigerating CIS (i.e., 4±1 °C), with storage in the dark and without agitation seems to guarantee the best viability and performance against D. gallinae, thus it can be considered the most appropriate storage method.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
