Figure 4 - Modulation of rhizobial mutualism byTrichoderma species. The ratio between values of symbiosis quality obtained from the S. meliloti /Trichodermacombinations and the S. meliloti alone are reported (trt/ctr). Values above 1 indicate that Trichoderma exert a positive effect non symbiosis quality (synergism), below 1 indicate a negative effect ofTrichoderma on symbiosis quality. TG, T. gamsii ; TH,T. harzianum ; TV, T. velutinum ; TT, T. tomentosum .