In vitro and in planta potential effect of some indigenous antagonists against Fusarium and pythiaceous species associated with peach seedlings decline

Background The effect of Aspergillus spp. and Trichoderma harzianum isolates was evaluated against the growth of Fusarium oxysporum, F. solani, Pythium ultimum and Phytophthora citrophthora affecting peach seedlings. Results The in vitro results revealed the ability of these antagonistic in reducing the radial growth of these pathogens. The most important mycelial growth reduction was of 85.82%, recorded for F. oxysporum in confrontation with A5 of Aspergillus candidus. Aspergillus flavus A4 and A. niger A10 were the most effective against F. solani with an inhibition percent more than 60%. For P. citrophthora, A. flavus A4, A. candidus A5, A. terreus A9 and A. niger A10 inhibited the mycelia growth by more than 60%. Aspergillus nidulans A1 was the most effective against Pythium ultimum (72.07%). Trichoderma harzianum isolates T9 and T10, are the most effective with a high inhibition percent of mycelial growth. The inhibition induced after 4 days of incubation, against F. oxysporum, F. solani, P. citrophthora and Pythium ultimum by these 2 antagonists exceeded 70, 60, 70 and 80%, respectively. The in planta test showed the efficacy of antagonists tested solo against some pathogens. In fact, Bacillus subtilis improved the health status by 62.55% compared to the control inoculated with P. ultimum. Trichoderma harzianum T9 significantly reduced the root rot index by 87.5% than the control inoculated with F. solani. In the same sense, B. subtilis significantly reduced this parameter by 62.55 and 88.89% than the control inoculated with P. ultimum and P. citrophthora, respectively. Furthermore, B. subtilis (B) and Aspergillus niger A10 improved plants height than the control inoculated with Pythium ultimum by 31.52 and 40.49%, respectively. However, the combinations of antagonists (T9 + T10; A5 + A10 and B + T10) did not improve their efficacy. Conclusions The isolates T. harzianum (T9 and T10), A. candidus A5 and A. niger A10 were the most effective in vitro against Fusarium, Pythium and Phytophthora species associated with peach seedling decline. The in vivo assay showed the effectiveness of B. subtilis against P. ultimum and P. citrophthora and the potential effect of T. harzianum T9 against F. solani. Their combinations revealed to be ineffective.