Use of GFP-tagged Trichoderma harzianum as a tool to study the biological control of the potato cyst nematode Globodera pallida

Abstract

The fungus Trichoderma harzianum strain ThzID1-M3 isolated in the Palouse region of the state of Idaho and transformed to express green fluorescent protein (GFP) was used as a biomarker to study the biological control processes of the potato cyst nematode Globodera pallida. Experiments were conducted to evaluate the effect of T. harzianum ThzID1-M3 on G. pallida infection and reproduction at 45 and 75days after inoculation respectively; and to observe, through microscopy rhizosphere chamber, the colonization of G. pallida second-stage juveniles and potato rhizoplane by T. harzianum ThzID1-M3 10days after inoculation. Significant reduction of G. pallida infection in potato roots was observed when soil was amended with T. harzianum ThzID1-M3. Globodera pallida cysts recovered from soil and G. pallida reproduction rate were significantly reduced by 49% and 60% respectively, when soil was amended with T. harzianum ThzID1-M3 compared to the non-amended soil. Microscopic observations showed that T. harzianum ThzID1-M3 colonized G. pallida second-stage juveniles and cysts, and proliferated in the rhizoplane and rhizosphere of potato. To our knowledge, this is the first report on the study of Trichoderma spp. marked with GFP against a potato cyst nematode. The use of GFP-tagged T. harzianum has the potential to monitor the biological control processes of G. pallida and the tools advanced in this study should facilitate the design of novel strategies to control this economically important nematode pest of potato.