# In Vitro Compatibility of Three Native Isolates of _Trichoderma_ with the Insecticide Chlorpyrifos
## 4 Discussion  
The results of the spore germination of the three native _Trichoderma_ strains (Figure 1) can be compared with other studies. [PERSON] [45] reported 41.33 and 14% germination of the _T. harzianum_ spores in a medium with chloropyrifos and at a concentration of 2000 mg/L and 2500 mg/L, respectively, while at 3000 mg/L, germinations were inhibited. In another investigation, the spore germination of eight _Trichoderma_ isolates reached 100% after 24-48 h of incubation when treated with chloropyrifos (500 mg/L) [46]. It is evident that the control group and the potato sucrose broth represent a favorable medium to induce  
Figure 3: In vitro antagonism of the three native _Trichoderma_ strains (TCA 3, 21, 23) against _Botrytis_ sp. in dual culture. Each _Trichoderma_ previously grew in different concentrations of chloropyrifos: 960 mg/L (**a**), 1200 mg/L (**b**), and 1440 mg/L (**c**). Figure 2: Effect of three concentrations of chloropyrifos on the mycelial growth (mm) of _T. asperellum_ TCA 3 (**a**), _T. asperellum_ TCA 21 (**b**), and _T. harzianum_ TCA 23 (**c**). Maximum diameter of the three strains at 96 hours of incubation. The same letters mean that there are no significant differences according to [PERSON]’s test (\(p<0.05\)). Error bars represent the standard deviation (SD) of the mean values \(\pm\) SD of 2 readings per 3 replicates. the germination of the spores of the three strains of _Trichoderma_, which went through a series of stages such as the isotropic phase or swelling, the polarization of the cells, the emergence of the hyphae, and finally its elongation [47]. However, when the medium was mixed with chlorpyrifos, spore germination was affected according to the concentration of the insecticide. This could be related to the dormancy stage of the spores and their concentration [48]. In this sense, a large number of spores within the inoculum could have maintained the latency stage due to the accumulation of germination auto-inhibitors [47]. Additionally, the nutrients of the potato sucrose broth may have stimulated the germination of the spores in the three concentrations. However, high chlorpyrifos concentrations may have limited the germination percentage, which would explain different values in each _Trichoderma_ strain evaluated. The participation of other germination induction mechanisms is not ruled out. Figure 2 shows the effect of chlorpyrifos on the mycelial growth of native strains. The values reached were similar to those reported in other investigations, such as that of [PERSON] [45], where _T. harzianum_ reached a maximum diameter of 43 mm when the medium had a concentration of 2000 mg/L of chlorpyrifos. On the other hand, [PERSON] et al. [49] used 48% chlorpyrifos, which affected the in vitro growth of autochthonous _Trichoderma_ isolates, which reached colony diameters of less than 30 mm. Likewise, [PERSON] et al. [50] showed that a species of _T. harzianum_ was affected in its growth when it was treated with doses higher than 5 mg/L of chlorpyrifos. In another study, [PERSON] et al. [51] found that when the concentration of chlorpyrifos exceeded a threshold level, there was a negative effect on microbial populations. To explain the different values of the mycelial growth of the _Trichoderma_ strains (Figure 2), it is important to consider the formation of the hypha. Nutrients are uptaken at the apical part of the hypha and transferred to the interior regions of the fungus for the development and formation of the next generation of spores [52]. In this apical zone of the hypha, the enzymes (exoenzymes) responsible for the degradation of chlorpyrifos can be found. On the other hand, the uptake of nutrients and chlorpyrifos can be explained by mediating cometabolism, which occurs when there is the presence of another carbon source in the medium, such as sugars, etc. [41], as occurs in the media used in this investigation.