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Isolation and characterization of Exserohilum turcicum, and its in vitro inhibition by volatile organic compounds produced by rhizobacteria

By Estefanía Fonseca Chávez, Irvin Alonso Molina Marañón, Luz Irela Lugo Zambrano, Juan Carlos Martínez Álvarez, Guadalupe Arlene Mora Romero, Jesús Damián Cordero Ramírez, Karla Yeriana Leyva Madriga*

* Corresponding Author. Email: / Institution:

Accepted: 13/November/2024 – Published: 04/December/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2024-14

Abstract Background/Objective. Biological control offers new strategies for disease management in agriculture. In the present study, the antifungal activity of volatile organic compounds (VOCs) emitted by rhizobacteria, was evaluated in the growth and infective capacity of four isolates of E. turcicum obtained from symptomatic corn plants, in northern Sinaloa.

Materials y methods. The fungal isolates were characterized morphologically and molecularly, and their pathogenicity was corroborated in a detached leaf assay. The ability of VOCs to inhibit mycelial growth and infection of maize leaves by E. turcicum was evaluated in in vitro assays, in divided Petri dishes. Bacterial hydrogen cyanide production was qualitatively determined.

Results. The mycelial growth of E. turcicum was reduced by VOCs of at least one rhizobacteria, registering inhibitions between 22% and 63%. Leaves infection was reduced between 63% and 98% in the presence of rhizobacterial VOCs. Hydrogen cyanide production was detected in strains B3 and B9.

Conclusion. Strain B95 was more effective in reducing mycelial growth and infection by E. turcicum. The production of hydrogen cyanide could be involved in its antagonistic effect. In-plant tests are required to corroborate its effectiveness, as well as characterize its volatile profile.

Keywords: Biocontrol, Bacillus, Pseudomonas, leaf blight, volatile compounds.

Figure 1. Characterization of Exserohilum turcicum isolates. <strong>A-C)</strong> Morphological characteristics of representative isolate Bac7-2. A) Frontal view of the culture in PDA; <strong>B)</strong> Reverse view of the culture in PDA; <strong>C)</strong> Conidium; <strong>D)</strong> Maximum Likelihood phylogram inferred from the combined matrix of the markers act+ITS+rpb2 from Exserohilum.
Figure 1. Characterization of Exserohilum turcicum isolates. A-C) Morphological characteristics of representative isolate Bac7-2. A) Frontal view of the culture in PDA; B) Reverse view of the culture in PDA; C) Conidium; D) Maximum Likelihood phylogram inferred from the combined matrix of the markers act+ITS+rpb2 from Exserohilum.
Figure 2. Pathogenicity test. <strong>A)</strong> Detached leaf system used to confirm the pathogenicity; <strong>B)</strong> Symptoms caused by the <em>Exserohilum turcicum</em> isolates in the detached maize leaves.
Figure 2. Pathogenicity test. A) Detached leaf system used to confirm the pathogenicity; B) Symptoms caused by the Exserohilum turcicum isolates in the detached maize leaves.
Figure 3. Effect of the bacterial volatile organic compounds on the mycelial growth of <em>Exserohilum turcicum</em> in divided Petri dishes.
Figure 3. Effect of the bacterial volatile organic compounds on the mycelial growth of Exserohilum turcicum in divided Petri dishes.
Figure 4. Effect of the bacterial volatile organic compounds on the infective capacity of <em>Exserohilum turcicum</em> on detached maize leaves.
Figure 4. Effect of the bacterial volatile organic compounds on the infective capacity of Exserohilum turcicum on detached maize leaves.
Figure 5. Detection of volatile hydrocyanic acid emitted by rhizobacteria.
Figure 5. Detection of volatile hydrocyanic acid emitted by rhizobacteria.
Table 1. Effect of the bacterial volatile organic compounds (VOCs) on the mycelial growth of <em>Exserohilum turcicum</em> in divided plates.
Table 1. Effect of the bacterial volatile organic compounds (VOCs) on the mycelial growth of Exserohilum turcicum in divided plates.
Table 2. Effect of the bacterial volatile organic compounds (VOCs), in the infective capacity of <em>Exserohilum turcicum</em> in detached maize leaves.
Table 2. Effect of the bacterial volatile organic compounds (VOCs), in the infective capacity of Exserohilum turcicum in detached maize leaves.