Induction of defense responses by extracts of spent mushroom substrates in rice.

We investigated the effect of treatment with hot water extracts from the spent mushroom substrates (SMSs) of and on the resistance of rice leaves to infection. The spraying of the SMS extracts clearly suppressed the development of lesions caused by infection. The accumulation of phytoalexins momilactones A and B, oryzalexin A, and sakuranetin was markedly induced by the spraying of extracts. The enhanced expression of defense related genes and was also found in leaves sprayed with the extracts. Treatments with the extracts also affected phytohormone levels. The levels of -(Δ-isopentenyl)adenine and -zeatin markedly increased in response to treatment, whereas the levels of salicylic and jasmonic acids were largely unchanged.