|500-1||Minimum inhibitory concentrations of menadione to entomopathogenic fungi|
|Autores:||Rosana F. F. Azevedo (UNIVAP - Universidade do Vale do Paraíba) ; Roberta K. F. Souza (UNIVAP - Universidade do Vale do Paraíba) ; Drauzio Eduardo Naretto Rangel (UNIVAP - Universidade do Vale do Paraíba) |
Oxidative stress is caused by reactive oxygen species (ROS), including superoxide ion, hydrogen peroxide, and hydroxyl radicals. Several types of stress condition, including heat, UV-A radiation, and chemical products (diamide, paraquat, menadione, sodium chloride, and several others) are potent ROS inducers. Entomopathogenic fungi are predisposed to heat and UV-A radiation when outside the insect host. When inside the host, they are subject to phagocytic cells that generate ROS to eliminate invading pathogens. To better understand the oxidative stress tolerance of the entomopathogenic fungi, Beauveria bassiana (ARSEF 252), Metarhizium acridum (ARSEF 324), Aschersonia aleyrodis (ARSEF 430, and 10276), Metarhizium brunneum (ARSEF 1187), Metarhizium robertsii (ARSEF 2575), Tolypocladium cylindrosporum (ARSEF 3392), Isaria fumosorosea (ARSEF 3889), Tolypocladium inflatum (ARSEF 4877), Metarhizium brunneum (ARSEF 5626), Metarhizium anisopliae s.l. (ARSEF 5749), Simplicillium lanosoniveum (ARSEF 6430), Lecanicillium aphanocladii (ARSEF 6433), Simplicillium lanosoniveum (ARSEF 6651), and Aschersonia placenta (ARSEF 7637) were exposed to a strong superoxide-generating agent: menadione sodium bisulphate. The conidial germination was evaluated 24 h after inoculation on potato dextrose agar (PDA) (control) or PDA supplemented with menadione with 20 different concentrations from 0.01 to 0.20 mM, with increments of 0.01 mM. The plates were maintained at 26 C in the dark. Lethal dose 50, lethal dose 84, and minimum inhibitory concentrations (MIC) were calculated. The two Aschersonia species (ARSEF 430, 7637, and 10276) were the most susceptible fungi, followed by the two Tolypocladium species (ARSEF 3392 and 4877) and the M. acridum (ARSEF 324). Metarhizium brunneum (ARSEF 5626) and M. anisopliae s.l. (ARSEF 5749) were the most tolerant isolates with MIC 0.28 mM. All fungal isolates, except ARSEF 5626 and ARSEF 5749, were not able to germinate at 0.20 mM. However, ARSEF 5626 from Finland and ARSEF 5749 from Mexico are the most susceptible isolates to heat and UV-B radiation. M. acridum (ARSEF 324) from Australia, on the other hand, is the most tolerant isolate to UV-B radiation and heat but was very susceptible to menadione.
Palavras-chave: oxidative stress, entomopathogenic fungi, menadione