Abstract
Trichoderma species are known as excellent biocontrol agents against soil-borne pathogens that cause considerable crop losses. Eight strains of Trichoderma were isolated from five Egyptian regions. They identified based on translation elongation factor-1α (TEF1) sequencing as four different Trichoderma species: Trichoderma asperellum, Trichoderma harzianum, Trichoderma viride, and Trichoderma longibrachiatum. Optimal growth conditions (temperature and media), and the phosphate solubilization capability of Trichoderma strains were evaluated in vitro. Further, the ability of these strains to antagonize Fusarium solani, Macrophomina phaseolina, and Fusarium graminearum was also evaluated. The results revealed that Trichoderma harzianum (Th6) exhibited the highest antagonistic ability against F. solani, M. phaseolina and F. graminearum with inhibition rates of 71.42%, 72.97%, and 84.61%, respectively. Trichoderma viride (Tv8) exhibited the lowest antagonism against the same pathogens with inhibition rates of 50%, 64% and 69.23%, respectively. Simple-sequence repeats (SSRs) and random amplified polymorphic DNA (RAPD) markers were used to evaluate the genetic variability of the Trichoderma strains. The results revealed that of 45 RAPD amplified bands, 36 bands (80%) were polymorphic and of SSRs amplified 36 bands, 31 bands (86.11%) were polymorphic. The amplification of calmodulin and β-1,3-endoglucanase was noted at 500 bp and 230 bp, respectively. Data indicated that T. viride (Tv8) had the highest phosphate solubilization index (10.0 mm), while T. harzianum (Th6) had the lowest phosphate solubilization index (4.0 mm). In conclusion, T. harzianum (Th6) had the highest antagonistic activity in dual culture assay along with the growth rate; while T. viride (Tv8) had the highest phosphate solubilization activity. There are still gaps in obtaining new formulations, selecting potent Trichoderma strains to confirm disease control in planta. For improving Trichoderma recommendation in the organic agricultural system and sustaining the fertility of the soil, the field application of highly antagonistic biocontrol agents in different types of soil and plant species will be the first approach toward bio-pesticide treatments along with bio-fertilizer inoculation. Furthermore, secondary metabolites will be investigated for the most promising strains with the combination of different pathogens and application timing.
Highlights
Plant health and crop production are constantly under threat from biotic constraints, especially fungal diseases caused by various species of soil fungal pathogens
A tree containing eight strains of Trichoderma was drawn; the tested strains were found to be closed to four taxa of Trichoderma belonging to T. harzianum (Th3, Th4, Th6 and Th7), two strains were classified as
The results showed that the isolates Th7 and inhibited M. phaseolina as they grew superficially along with its colony and inhibited its growth by percentage ranged from 64.05% to 72.97% (Figure 6I,II)
Summary
Plant health and crop production are constantly under threat from biotic constraints, especially fungal diseases caused by various species of soil fungal pathogens. Even though farmers believe that chemical fungicides can control these diseases, some already use them in combination biological control agents. These are of great attention as pesticides have unfavorable side impacts, and it is necessary to find an alternative method such as beneficial microbes to prevent human and environmental disasters. Several Trichoderma species are beneficial to host plants, providing one of the most promising alternatives for promoting plant growth [3] by increasing the plant health and its immunity, motivating mechanisms of plant defense, avoiding pathogen outbreaks and controlling plant disease [4,5]. T. harzianum [6]; T. asperellum [7];
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