Preliminary in vitro and nursery results to screen for Trichoderma isolates which are antagonistic to Ganoderma

Trichoderma is often used as a bio-control agent as part of an integrated approach for the management of Ganoderma. In this paper, we report results of in vitro investigations on the selection of antagonistic isolates of Trichoderma based on growth rates and capacity to sporulate but also some in vivo studies on the screening of these selected isolates in a large nursery trial. Laboratory trials were established in 2010 to investigate the growth rates and sporulation capacities of several Trichoderma isolates including T. koningii, T. viride, T. harzianum and some isolates of T, virens. The growth rates were assessed on Potato Dextrose Agar (PDA) and Trichoderma Selective Media (TSM) using a randomized design replicated four times. In addition, a nursery trial was later established using selected isolates from the in vitro studies. The aim of the nursery trial was to investigate the antagonism of different Trichoderma isolates in vivo. Rubber wood blocks (RWBs) were inoculated with Ganoderma to provide an inoculum source in the nursery polybag. There were twenty-seven treatments with thirteen different isolates tested using two factors (1. application of Trichoderma directly on top of inoculated RWBs and 2. complete mixing of Trichoderma with the soil in the nursery polybag). The trial had nine replicates with a factorial design. The antagonism of Trichoderma to Ganoderma was assessed by recording the percentage of seedlings showing Ganoderma symptoms (presence of Ganoderma basidiocarps and/or foliar symptoms). In vitro tests showed that Trichoderma isolate SBJ 8 had the fastest growth on both PDA and TSM media while T. koningii and T, viride sporulated profusely. Preliminary results from the nursery trial, showed that after 40 weeks of observation, TK (T. koningii M) when applied on the top of RWB had the lowest infection (26 %) and followed by T, harzianum isolate M (30 %) and SBJ 8 (35 %) infection. This was significantly different from the control treatment (no Trichoderma application) which had 78 % Ganoderma infection. Trichoderma application on the top of RWB significantly reduced Ganoderma infection compared with treatment where Trichoderma was mixed with soil. Selected isolates will be used for further studies in the field.