Comparative efficacy of different approaches to managing Meloidogyne incognita on green bean

Pre-treatment with Dazomet enhances the biocontrol efficacy of purpureocillium lilacinum to Meloidogyne incognita

BACKGROUND

Meloidogyne incognita greatly restricts the production of protected vegetables in China. Application of biocontrol agent Purpureocillium lilacinum is an important practice to control the nematode; however, instability usually occurs especially in heavily infested field. This study aimed to illustrate the high efficiency of P. lilacinum agent with fumigant Dazomet in vitro.

RESULTS

P. lilacinum YES-2-14 showed strong parasitic and nematicidal activities to M. incognita. Pre-treatment with Dazomet significantly enhanced the biocontrol effects of the fungus. After fumigation with Dazomet at a dosage of 7.5 mg kg- 1 soil, parasitism of YES-2-14 on M. incognita eggs increased by more than 50%. Meanwhile, when P. lilacinum fermentation filtrate treated following Dazomet fumigation at 10 and 20 mg kg- 1 soil, the mortalities of second-stage juveniles (J2s) increased by 110.2% and 72.7%, respectively. Both Dazomet and P. lilacinum significantly reduced the penetration ability of J2s to tomato roots. When P. lilacinum filtrate used alone, the J2s penetrating into the young roots decreased by 48.8% at 4 dpi; while in the combined treatment, almost no J2 was detected within the roots at 4 dpi and the number of knots reduced by more than 99% at 45 dpi, indicating a synergistic effect of the biocontrol fungus and fumigant.

CONCLUSIONS

Pre-treatment with Dazomet greatly increased the biocontrol efficacy of P. lilacinum to M. incognita. This research provides insight into the efficient management of plant parasitic nematodes and effective use of biocontrol agents.

Exploring the Potential Applications of Paecilomyceslilacinus 112

Microorganisms are widely used to obtain biostimulants that can facilitate the assimilation of nutrients, ensuring high crop yield and quality. A particular category of biostimulants are protein hydrolyzates (PH), obtained from microbial cultures grown on a nutrient medium. In the present study, Paecilomyces lilacinus 112, an endophytic fungus isolated from soil, was tested to determine its effect on the growth promotion of tomato seedlings in greenhouse conditions. Additionally, other beneficial features of the P.lilacinus isolate were evaluated via several tests: antagonism against plant pathogenic fungi, production of secondary useful metabolites, and solubilization of vital micronutrients. Out of the tested pathogens, P.lilacinus exhibited the highest antifungal activity against a Cladosporium isolate (inhibition of 66.3%), followed by Rhizoctonia. solani (52.53%), and Sclerotinia sclerotiorum (50.23%). Paecilomyceslilacinus 112 was able to secrete hydrolytic enzymes and siderophores, and solubilize zinc and phosphorus. In the tomato treatment, the application of PH obtained from fungal cultivation on a feather medium led to the following increases in plant growth parameters: 3.54-fold in plant biomass; 3.26-fold in plant height, 1.28-fold in plant diameter; 1.5-fold in the number of branches/plant; and 1.43-fold in the number of leaves/plant, as compared to water treatment. The application of this isolate can be of benefit to bioeconomy because keratin wastes are valorized and returned, in agriculture, contributing to renewable natural resources.

Paecilomyces and Its Importance in the Biological Control of Agricultural Pests and Diseases

Incorporating beneficial microorganisms in crop production is the most promising strategy for maintaining agricultural productivity and reducing the use of inorganic fertilizers, herbicides, and pesticides. Numerous microorganisms have been described in the literature as biological control agents for pests and diseases, although some have not yet been commercialised due to their lack of viability or efficacy in different crops. Paecilomyces is a cosmopolitan fungus that is mainly known for its nematophagous capacity, but it has also been reported as an insect parasite and biological control agent of several fungi and phytopathogenic bacteria through different mechanisms of action. In addition, species of this genus have recently been described as biostimulants of plant growth and crop yield. This review includes all the information on the genus Paecilomyces as a biological control agent for pests and diseases. Its growth rate and high spore production rate in numerous substrates ensures the production of viable, affordable, and efficient commercial formulations for agricultural use.

Identification and Characterization of Nematicidal Volatile Organic Compounds from Deep-Sea Virgibacillus dokdonensis MCCC 1A00493

Root-knot nematode diseases cause severe yield and economic losses each year in global agricultural production. Virgibacillus dokdonensis MCCC 1A00493, a deep-sea bacterium, shows a significant nematicidal activity against Meloidogyne incognita in vitro. However, information about the active substances of V. dokdonensis MCCC 1A00493 is limited. In this study, volatile organic compounds (VOCs) from V. dokdonensis MCCC 1A00493 were isolated and analyzed through solid-phase microextraction and gas chromatography-mass spectrometry. Four VOCs, namely, acetaldehyde, dimethyl disulfide, ethylbenzene, and 2-butanone, were identified, and their nematicidal activities were evaluated. The four VOCs had a variety of active modes on M. incognita juveniles. Acetaldehyde had direct contact killing, fumigation, and attraction activities; dimethyl disulfide had direct contact killing and attraction activities; ethylbenzene had an attraction activity; and 2-butanone had a repellent activity. Only acetaldehyde had a fumigant activity to inhibit egg hatching. Combining this fumigant activity against eggs and juveniles could be an effective strategy to control the different developmental stages of M. incognita. The combination of direct contact and attraction activities could also establish trapping and killing strategies against root-knot nematodes. Considering all nematicidal modes or strategies, we could use V. dokdonensis MCCC 1A00493 to set up an integrated strategy to control root-knot nematodes.