Work

Biological control of anthracnose (Colletotrichum gloeosporioides) and high-quality walnut production in walnut (Juglans regia L.) trees by Bacillus licheniformis PR2

Year: 2025

Type: article

Abstract: Walnut (Juglans regia L., Fam.: Juglandaceae) trees are an economically important crop worldwide, but their production is hampered by notorious diseases such as walnut anthracnose caused by Colletotrichum gloeosporioides. This study aims to demonstrate the potential of Bacillus licheniformis PR2 as an alternative to chemical fungicides and fertilizers in walnut production, by suppressing anthracnose disease and improving the yield and quality of kernels. B. licheniformis PR2 produced fungal cell wall degrading enzymes such as chitinase, β-1,3-glucanase and protease which degraded the fungal cell wall chitin, β-glucans and glycoproteins that constitute the cell wall of the C. gloeosporioides. Therefore, the crude enzyme fraction of B. licheniformis PR2 (100 µL/mL), inhibited spore germination and mycelial growth of C. gloeosporioides by 89.22% and 33.31%, respectively. Field application of B. licheniformis PR2 culture resulted in 3.60- and 3.47-fold reduction in anthracnose incidence compared to the conventional treatment and control groups, respectively. Additionally, B. licheniformis PR2 exhibited plant growth-promoting properties including the production of indole-3-acetic acid (up to 148.49 mg/mL), a phytohormone that promoted root development, and showed ammonium-N production and phosphate solubilizing potential, improving the availability of essential nutrients such as nitrogen by 1.70-fold and 1.56-fold and phosphorus by 2.57-fold and 2.67-fold in soil compared to the conventional treatment and control groups, respectively. This increased the chlorophyll content/photosynthetic potential, and improved the yield and physical characteristics (height, width and weight) of walnut kernels. Moreover, B. licheniformis PR2 increased the calcium content in walnut kernel by promoting calcium absorption from the soil through organic acid production and improved the kernel firmness by strengthening pellicle cell walls. Therefore, our study demonstrates its potential as an alternative to chemical fungicides and fertilizers of B. licheniformis PR2, a biological agent of inhibiting fungal pathogens and increasing the production of high-quality walnut kernels.

Source: Biological Control

DOI: 10.1016/j.biocontrol.2025.105871