تقييم التداخل بين بعض أنواع الفطر Trichoderma spp. و مبيد Topsin M في مكافحة مرض تعفن جذور الباميا

Evaluation of the interaction between some species of Trichoderma spp. and Topsin M pesticide in the fight against okra root rot

Abstract

This study aimed to isolate and diagnose the pathogen of seed and seedling rot disease from infected okra roots [Abelmoschus esculentus (L.) Moench] and its control using the chemical fungicide Topsin M and some species of Trichoderma spp. (T. atroviride, T. longibrachaitum, T. asperellum, and T. aspirelloides) and finding an integrated formula among them in the control of the pathogen. The current study also aimed at the possibility of manufacturing a biological preparation using different species of Trichoderma spp.. All the experiments of this study were carried out in the Plant Protection Department/ College of Agriculture/ Karbala University during the agricultural season 2020-2021.
The results showed the possibility of isolating 15 fungal isolates that were morphologically diagnosed to be species belong to Fusarium spp.. The results of the pathogenicity test of the 15 isolates in plastic pots proved that all isolates were pathogenic and the rates of inhibition of seed germination ranged between 0.00%-73.30%, with a significant difference from the percentage of germination in the control treatment, which amounted to 100%. Among those isolates, the isolate (5) was the most pathogenic compared to other isolates by preventing seed germination (0.00%) compared to isolate (1) which had little effect in reducing the percentage of seed germination (72.60%). The isolate 5 was diagnosed as Fusarium culmorum by relying on morphological as well as molecular characteristics and using the polymerase chain reaction technology (PCR) and determination of the sequence of nitrogenous bases.
The results proved that all species of Trichoderma spp. had a significant effect in inhibiting F. culmorum compared to control treatment (pathogenic fungus alone). The two species of T. harzianum (1) and T. aspirelloides (5) showed a high efficiency in inhibiting the growth of pathogenic funus (88.00% and 87.66%, respectively), while it was found that the lowest inhibition rate of the pathogenic fungus (66.66%) was for the fungus species (1). The results showed that there was an antagonistic ability between T. harzianum (1) and T. longibrachaitum (3) and T. asperellum (4), while T. harzianum (1) did not show antagonistic ability against species T. atroviride (2) and T. aspirelloides (5). It was observed that the highest inhibitory ability of Trichoderma spp. against F. culmorum when all the biological control fungi were present together in the same Petri-dish, the inhibition rate for the pathogenic fungus was 95%. The results also demonstrated that the concentrations (20, 40, 60, and 80%) of filtrate of Trichoderma spp. had a clear effect in increasing the germination rates of okra, maize, and radish seeds. The 100% concentration was the most encouraging for seed germination and an increase in the dry weight of the plants mentioned above.
The results also showed that the presence of Trichoderma spp. alone or together had a positive effect in increasing the content of peroxidase enzyme (POD) in okra plants compared to plants grown in soil not infested with any of the fungi as well as infested soil with F. culmorum, it was proved that the highest level of peroxidase enzyme (POD) was in plants grown in soil infested with all species of Trichoderma spp. and Fusarium culmorum, with an average of 6.87 units. mg protein-1 and T. aspirelloides (5) was the best among the other species in increasing the level of peroxidase enzyme (POD) with an average of 1.07 units. mg protein-1. As for the enzyme catalase, it was observed that its highest level was in plants grown in soil infested with Trichoderma spp. and F. culmorum amounting to 322.32 units. Mg. protein-1.
The results showed that Trichoderma spp. had an effect on stimulating the plant on the production of the hormone abscisic acid, at a rate of 13.22 mg. L-1, which differed significantly from its content in plants grown in the control treatment, which averaged 22.60 mg. L-1. The results also proved that the presence of the fungus Trichoderma spp. A clear role in increasing the plant content of gibberellin hormone (GA3), which was the highest level (85.09 mg. L-1) in plants grown in soil infested with all species of Trichoderma spp. compared to its content in the control plants (not infested with any fungus), which amounted to 43.33 mg. liter -1. It was also found that Trichoderma spp. used in this study, the ability to grow in most concentrations of the chemical pesticide Topsin M(0.25, 0.50, 0.75, 1.00, and 1.25 ml/ L) and the concentration was 0.25 ml/ L the least inhibiting for all species of Trichoderma spp., while the growth inhibition of the fungus F. culmorum under the influence of the same concentration 82.35%. It was verified when grown on sterilized and crushed baker’s medium and iron added to it at a concentration of 0.75 gm commercial substance/ liter and loaded on talc and stored in paper bags. m and stored in laboratory conditions with 105.96 and 96.77 reproductive units/ml, respectively. It was also found that the development of the fungus Trichoderma spp. On the ground and sterilized baker and storing it without any carrier material was the best in maintaining the vitality of the fungus Trichoderma spp. compared to its loading on the carriers (349.33 reproductive units/ ml), which encourages the use of sterilized and ground baker’s plant in growing Trichoderma spp. Species.