Molecular Microbiology Research 2024, Vol.14, No.3, 141-152 http://microbescipublisher.com/index.php/mmr 145 3.3 Nematicidal effects against root-knot nematodes Aspergillus oryzae also shows potential in controlling nematode infestations, particularly root-knot nematodes, which are a significant problem in rice cultivation. The nematicidal activity of A. oryzae is attributed to its ability to produce metabolites that are toxic to nematodes, thereby reducing their populations and minimizing crop damage. Studies on the nematicidal effects of A. oryzae have demonstrated that certain strains can effectively inhibit the growth and reproduction of root-knot nematodes. The metabolites produced by A. oryzae disrupt the nematodes' life cycle, leading to decreased infection rates and improved plant health. This mode of action is particularly advantageous as it offers a biological alternative to chemical nematicides, which can have adverse environmental impacts (Zhang et al., 2022). In conclusion, the antifungal, antibacterial, and nematicidal properties of Aspergillus oryzae highlight its potential as a versatile biological control agent in rice cultivation. Its ability to produce a wide range of bioactive metabolites makes it an effective tool in integrated pest management strategies aimed at reducing reliance on chemical pesticides and promoting sustainable agriculture. 4 Application Efficacy 4.1 Laboratory and field application techniques The application techniques of Aspergillus oryzae in biological control have been explored both in laboratory settings and field trials to assess their efficacy against various rice pests. Laboratory experiments typically involve controlled environments where variables such as temperature, humidity, and exposure time can be precisely regulated. For instance, in vitro studies on the nematicidal effects of A. oryzae have demonstrated significant reductions in nematode populations when applied at specific concentrations and incubation periods (Liu et al., 2019). Field application techniques, are more complex due to the variable environmental conditions. A common approach involves the use of A. oryzae spore suspensions sprayed directly onto rice plants. For example, large-scale field trials have shown that aerial spraying of A. oryzae spore suspensions can effectively reduce pest populations over extensive areas. In a study where A. oryzae was used against locusts, drone-assisted spraying resulted in significant reductions in locust populations, demonstrating the feasibility of this method for large-scale agricultural applications (You et al., 2023). Another effective method involves incorporating A. oryzae into soil treatments. By mixing fungal spores into the soil, it is possible to target soil-borne pests such as nematodes more directly. This method has been shown to reduce the incidence of root galls and nematode populations in rice roots, as seen in greenhouse studies where soil applications led to significant pest suppression (Liu et al., 2019). 4.2 Efficacy of different formulations and concentrations The application of synthetic The efficacy of Aspergillus oryzae in pest control can vary significantly depending on the formulation and concentration used. Different formulations, such as spore suspensions, dry spore powders, and fermented extracts, have been tested to determine the most effective method for delivering the biocontrol agent. Spore suspensions are commonly used due to their ease of application and effectiveness. Studies have shown that higher concentrations of spore suspensions generally result in greater pest mortality. For example, a study on the use of A. oryzae against nematodes found that a concentration of 5×107 spores/ml was more effective than lower concentrations, resulting in higher mortality rates and reduced nematode reproduction (Liu et al., 2019). Fermented extracts of A. oryzae have also been tested for their efficacy. These extracts contain not only fungal spores but also secondary metabolites produced during fermentation, which can enhance the biocontrol effects. For instance, the use of fermented rice extracts with A. oryzae demonstrated significant antifungal activity against rice pathogens, suggesting that these formulations could be particularly effective in integrated pest management programs (Shoji et al., 2021).
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