Decomposition of grass leaves by ligninolytic litter-decomposing fungi

The abilities of litter-decomposing fungi (LDF) to remove lignin from leaves of a perennial grass, Miscanthus sinensis, were examined under pure culture conditions. A total of 12 fungal isolates were tested, including eight isolates of seven basidiomycete and one ascomycete species that are ligninolytic on tree leaf litter and four isolates of another ascomycete species, Nigrospora sphaerica, obtained from M. sinensis leaves. Mass loss of leaves caused by the 12 isolates ranged from 4.7 to 43.1% of the original leaf mass. Trametes versicolor caused the greatest mass loss of lignin, followed by Marasmius sp. and Gerronema nemorale, whereas Mycena polygramma and the four isolates of N. sphaerica had limited abilities to cause mass loss of lignin. Trametes versicolor caused the greatest mass loss of total carbohydrates, followed by Marasmius sp., two isolates of N. sphaerica, and G. nemorale, whereas Pseudoclitocybe cyathiformis, Coccomyces sp., and Clitocybe gibba had limited abilities to cause mass loss of total carbohydrates. Mass loss of lignin was significantly and positively correlated with mass loss of leaves for the seven isolates that showed marked ligninolytic activities. In separate experiments, leaves previously partly decomposed by three ligninolytic fungi were used in pure culture tests to evaluate the effects of the pretreatment of grass leaves by ligninolytic fungi on subsequent utilization of substrates by fungi with limited ligninolytic activities. The pretreatment of M. sinensis leaves with three ligninolytic fungi generally suppressed the subsequent decomposition of lignin, total carbohydrates, or both by N. sphaerica. The results demonstrate that ligninolytic LDF are capable of removing lignin effectively from grass leaves.