Sexually competent, sucrose- and nitrate-assimilating strains of Hypocrea jecorina (Trichoderma reesei) from South American soils

Three new strains of Trichoderma reesei, the anamorph of Hypocrea jecorina, are reported from soil in French Guiana and Brazil. Identification of the strains as T. reesei/ H. jecorina was confirmed by analysis of the internal transcribed spacer regions 1 and 2 of the nuclear rDNA cluster and by their ability to produce the teleomorph when mated with the appropriate strains. Hypocrea jecorina is considered to reproduce primarily sexually, as opposed to other Hypocrea and Trichoderma species where asexual reproduction predominates. Like the original isolate of T. reesei, QM 6a, all three new isolates exhibited cellulolytic activities. In contrast to QM 6a, however, they grew on sucrose as sole carbon source and on nitrate as sole nitrogen source, thus indicating that these substrate utilization criteria are not taxonomically reliable in Hypocrea (Trichoderma). The nonutilization of sucrose and nitrate in QM 6a is due to a lack of the uptake system for sucrose and of nitrite reductase activity, respectively, in that culture. Comparison of QM 6a and the three new isolates revealed that all H. jecorina isolates produce intracellular but not extracellular invertase. The potential for using these strains in the improvement of the commercially exploited strain of T. reesei, QM 6a, is discussed.