RESUMO
Fusarium sudanense is a novel fungus recently isolated from asymptomatic samples of wheat grains in Argentina. The fungus caused symptoms of seedling blight and seed rot on wheat after artificial inoculations. It is known that the production of mycotoxins by pathogens belonging to the Fusarium genus is harmful to human and animal health. Moreover, the warm and humid conditions that are favorable for growth and mycotoxin production of these species put the Argentinian wheat production area at a high risk of mycotoxin contamination with this novel pathogen. The aim of this work was to evaluate the antagonistic effect of Trichoderma harzianum against F. sudanense under in vitro tests at different environmental conditions. Fungi were screened in dual culture at different water activities (αw) (0.995, 0.98, 0.95, and 0.90) and temperatures (25 and 15 °C). The growth rate of the fungi, interaction types, and dominance index were evaluated. Also, the interaction between T. harzianum and F. sudanense was examined by light and cryo-scanning microscopy. T. harzianum suppressed the growth of F. sudanense at 0.995, 0.98, and 0.95 αw at 25 °C and 0.995 and 0.98 αw at 15 °C. Macroscopic study revealed different interaction types between F. sudanense and T. harzianum on dual culture. Dominance on contact where the colonies of T. harzianum overgrew the pathogen was the most common interaction type determined. The competitive capacity of T. harzianum was diminished by decreasing the temperature and αw. At 0.95 αw and 15 °C, both fungi grew slowly, and interaction type "A" was assigned. Microscopic analysis from the interaction zone of dual cultures revealed an attachment of T. harzianum to the F. sudanense hyphae, penetration with or without formation of appressorium-like structures, coiling, plasmolysis, and a veil formation. According to our results, T. harzianum demonstrated capability to antagonize F. sudanense and could be a promising biocontrol agent.
RESUMO
The effects of temperature (15 and 25 degrees C), water activity (0.85, 0.90, 0.95, 0.98 y 0.995) and the interaction between Fusarium sambucinum and Phoma glomerata in rice extract agar on fungus growth were investigated. Fungi interactions were given a numerical score to obtain an Index of Dominance (ID) and to observe possible variations under different conditions of temperature and water activity (aw) changed. F. sambucinum and P. glomerata grew most rapidly -both individually and paired- at 0.995 aw and 25 degrees C. On the other hand, F. sambucinum presented higher growth rates than P. glomerata and it was dominant over P. glomerata under all the tested conditions. Water activity and temperature showed a significant effect on fungus growth.
Assuntos
Ascomicetos/crescimento & desenvolvimento , Fusarium/crescimento & desenvolvimento , Micologia/métodos , Meios de Cultura/farmacologia , Técnicas In Vitro , Oryza , Extratos Vegetais/farmacologia , Temperatura , ÁguaRESUMO
Se estudió el efecto de la temperatura (15 y 25 ºC), la actividad de agua(0,85; 0,90; 0,95; 0,98 y 0,995) y la interacción entre Fusarium sambucinumy Phoma glomerata sobre el crecimiento de estas especies en agar extractode arroz. Además, a las interacciones se les asignó un valor numérico paraobtener el índice de dominancia (ID), analizando su posible variación alcambiar las condiciones de temperatura y actividad de agua (aw).Ambas especies presentaron un máximo crecimiento tanto individualmentecomo combinadas a 0,995 aw y 25 ºC. Por otra parte, F. sambucinum tuvoratios de crecimiento mayores que P. glomerata en todas las condicionesensayadas, dominando sobre este cuando interaccionaron. La actividad deagua y la temperatura tuvieron un efecto significativo sobre el crecimiento(AU)
The effects of temperature (15 and 25 ºC), water activity (0.85, 0.90, 0.95, 0.98y 0.995) and the interaction between Fusarium sambucinum and Phomaglomerata in rice extract agar on fungus growth were investigated.Fungi interactions were given a numerical score to obtain an Index ofDominance (ID) and to observe possible variations under different conditions oftemperature and water activity (aw) changed. F. sambucinum and P. glomeratagrew most rapidly -both individually and paired- at 0.995 aw and 25 ºC.On the other hand, F. sambucinum presented higher growth rates thanP. glomerata and it was dominant over P. glomerata under all the testedconditions. Water activity and temperature showed a significant effect onfungus growth(AU)
