Suppression of Nigrospora oryzae (Berk. & Broome) Petch by an aggressive mycoparasite and competitor, Penicillium oxalicum Currie & Thom.

The objective of this research was to study by means of different techniques, the interaction between Penicillium oxalicum and Nigrospora oryzae under different temperatures (15 and 25 degrees C), water activities (0.95, 0.98, and 0.995) and culture media (rice and rice extract agar). In dual culture, P. oxalicum was dominant over N. oryzae in spite of presenting in the majority of cases, lower growth rates. The microscopic study revealed that P. oxalicum is a powerful mycoparasite, which attacks the conidiophores and the spores of N. oryzae, not only surrounding them, but also penetrating, deforming, destroying and developing reproductive structures inside them. The antagonist did not change its way of performance in the different tested conditions. Water activity and temperature showed a significant effect on fungus growth.