Mexican Journal
of Phytopathology

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• Scientific Article

Fusarium solani associated with Cedrela odorata and Swietenia macrophylla and their sensitivity to conventional fungicides

By Alejo Jairo Cristóbal*, José María Tun Suárez, Arturo Reyes Ramírez, Alberto Uc Várguez, Silvia Edith García Díaz

* Corresponding Author. Email: / Institution: Tecnológico Nacional de México/Instituto Tecnológico de Conkal

Accepted: 01/July/2024 – Published: 12/July/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2405-5

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Abstract Background/Objective. In the state of Yucatan, Mexico, 10 million forest plants were produced in the last five years for various conservation and restoration actions. The main limitations in the production of these plants in nursery are disease induced by the genus Fusarium spp., that cause stem and root rots and plant production losses of up to 50%. The objective of the work was to identify the causal agent associated with stem and root rot and necrosis of cedar (Cedrela odorata) and mahogany (Swietenia macrophylla) and their in vitro sensitivity to conventional fungicides.

Materials and Methods. C. odorata and S. macrophylla plants were collected at three and six weeks of germination, respectively, with symptoms of necrosis and rot indicated; from where five fungal isolates were obtained and morphologically and molecularly identified. The Minimum Inhibitory Concentration (MIC) of spores and the Minimum Lethal Concentration (MLC) of six conventional fungicides of recurrent application in the region (Prochloraz, Carbendazim, Benomyl, Fosetyl Al, Captan and Mancozeb) were determined in vitro by the microdilution method and validate their effectiveness and viability in the management of this problematic.

Results. The morphology and molecular sequences of the isolates were similar to the reported for Fusarium solani. The MIC of F. solani spores for Prochloraz, Carbendazim, Benomyl, Captan and Mancozeb were 2.44. 11.38, 14.06, 7.81 and 7.81 ppm, respectively; Fosetyl Al, did not inhibit spore germination normal mycelial growth of the fungus was observed at the concentration evaluated.

Conclusion. Prochloraz and Mancozeb had the lowest MLC with 2.44 and 7.81 ppm, respectively.

Keywords: cedar, mahogany, root of rot, nursery, chemical control

Figure 1. Plants with symptoms of necrosis and rot in the stem and root. A, B, and C) Cedrela odorata plants. D, E, and F) Swietenia macrophylla plants

Figure 2. A and D) View of 14-day-old Fusarium solani isolated from Cedrela odorata and Swietenia macrophylla, B) Septate mycelium and microconidia of F. solani, C) Macroconidia (3-4 septa) and microconidia (0-1 septum) of F. solani observed at 100X magnification, E) Macroconidia and microconidia observed at 40X magnification, and F) Sporodochia

Figure 3. Fungicidal effect of Prochloraz and Mancozeb on the spore solution of Fusarium solani obtained from the microdilution plate after two days of evaluation. A) Distribution in Petri dishes with PDA medium of five MIC obtained from Prochloraz, B and C) No mycelial growth of F. solani in the MIC of Prochloraz evaluated after 24 and 48 h, D) Distribution in Petri dishes with PDA medium of five MIC obtained from Mancozeb, E and F) No mycelial growth of F. solani in the MIC of Mancozeb evaluated after 24 and 48 h

Table 1. Conventional fungicides evaluated for their effect on spore germination and mycelial growth of Fusarium solani isolated from Cedrela odorata and Swietenia macrophylla.

Table 2. Minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) of conventional fungicides against Fusarium solani isolated from Cedrela odorata and Swietenia macrophylla