Population dynamics of Trichoderma species in the rhizosphere of tobac co and four species form China

摘要

To study the effect of tobacco growth on Trichoderma population, we in vestigated the occurrence of Trichoderma species in the rhizosphere of tob acco plant during the period from transplanting (June) to harvesting (October) and measured relative environmental factors. Eleven species of Trichoderma we re isolated, among which T.harzianum, T.viride, T.hamatum, T.atroviride, T.lo ngibrachiatum, T.virens, T.koningii were identified, other four species Ty1, Ty2, Ty3, Ty4 are new species. Of the species which occurred at high frequencies , T.harzianum and T.hamatum were most abundant in the July and T. viride in the August. The occurrence of the above three abundant species corr elates significantly with the developmental phase of tobacco and correlates appa rently with the soil moisture content, but not with the temperature. For the oth er eight species, no obvious correlation was found between the above factors and them. Based on nucleotide sequences of the internal transcribed spacer (ITS) regions of the rDNA cluster (ITS1and 2) and partial sequences of translation elongation f ac tor 1-alpha (tef1a), phylogenetic position of four new species was determined. Ty2 is additions to Trichoderma section and Ty3.Ty9.Ty10 are additions to sec tion Pachybasium.