This study demonstrates that the root-associated fungus Kosakonia oryziphila NP19, isolated from rice roots, is a promising plant growth-promoting biopesticide and biochemical agent for the control of rice blast. In vitro experiments were conducted on fresh leaves of Khao Dawk Mali 105 (KDML105) aromatic rice seedlings. The results showed that NP19 effectively inhibited the germination of rice blast fungal conidia. Fungal infection was inhibited under three different treatment conditions: rice inoculation with NP19 and fungal conidia; simultaneous leaf inoculation with NP19 and fungal conidia; and leaf inoculation with fungal conidia followed by NP19 treatment 30 h later. Furthermore, NP19 reduced fungal hyphal growth by 9.9–53.4%. In pot experiments, NP19 increased peroxidase (POD) and superoxide dismutase (SOD) activities by 6.1% to 63.0% and 3.0% to 67.7%, respectively, indicating enhanced plant defense mechanisms. Compared with uninfected NP19 controls, NP19-infected rice plants showed an increase in pigment content by 0.3%–24.7%, the number of full grains per panicle by 4.1%, the yield of full grains by 26.3%, the yield mass index of the yield by 34.4%, and the content of the aromatic compound 2-acetyl-1-pyrroline (2AP) by 10.1%. In rice plants infected with both NP19 and blast, the increases were 0.2%–49.2%, 4.6%, 9.1%, 54.4%, and 7.5%, respectively. Field experiments showed that rice plants colonized and/or inoculated with NP19 exhibited an increase in the number of full grains per panicle by 15.1–27.2%, full grain yield by 103.6–119.8%, and 2AP content by 18.0–35.8%. These rice plants also exhibited higher SOD activity (6.9–29.5%) compared to blast-infected rice plants not inoculated with NP19. Postinfection foliar application of NP19 slowed lesion progression. Thus, K. oryziphila NP19 was shown to be a potential plant growth promoting bioagent and biopesticide for the control of rice blast.
However, the effectiveness of fungicides is influenced by many factors, including the formulation, timing and method of application, disease severity, the effectiveness of disease forecasting systems, and the emergence of fungicide-resistant strains. Furthermore, the use of chemical fungicides can cause residual toxicity in the environment and pose a health risk to users.
In the pot experiment, rice seeds were surface sterilized and germinated as described above. They were then seeded with K. oryziphila NP19 and transplanted into seedling trays. The seedlings were incubated for 30 days to allow rice seedlings to emerge. The seedlings were then transplanted into pots. During the transplantation process, the rice plants were fertilized to prepare them for infection with the fungus that causes rice blast and to test their resistance.
In a field experiment, germinated seeds infected with Aspergillus oryzae NP19 were treated using the method described above and divided into two groups: seeds infected with Aspergillus oryzae NP19 (RS) and uninfected seeds (US). Germinated seeds were planted in trays with sterilized soil (a mixture of soil, burnt rice husk, and manure in a 7:2:1 ratio by weight) and incubated for 30 days.
oryziphila conidial suspension added to R rice and after 30 h of incubation, 2 μl of K. oryziphila NP19 was added at the same location. All Petri dishes were incubated at 25°C in the dark for 30 hours and then incubated under continuous illumination. Each group was replicated three times. After 72 hours of incubation, plant sections were examined and subjected to scanning electron microscopy. Briefly, plant sections were fixed in phosphate-buffered saline containing 2.5% (v/v) glutaraldehyde and dehydrated in a series of ethanol solutions. Samples were critical-point dried with carbon dioxide, then gold-coated and observed under a scanning electron microscope for 15 minutes.
Post time: Oct-13-2025