Background/Objetive.

Coconut palm (Cocos nucifera) is an important crop in Mexico. In Tabasco, the “Enano Verde del Brasil” (CEVB) variety has been introduced to produce green fruit for coconut water; however, pathological problems of unknown etiology have been observed. The objective of this study was to identify the fungi associated with trunk rot of CEVB coconut in Tabasco, Mexico, and to conduct a comparative in vitro evaluation of the efficacy of systemic and contact fungicides.

Materials and Methods.

Fungal isolation in PDA medium was carried out from trunk, spear, and inflorescence samples showing necrosis. The isolates were initially characterized by morphological analysis. Two of them were selected for pathogenicity tests on CEVB seedlings and identified molecularly through the analysis of partial sequences of the ITS gene (ITS1-5.8S-ITS2 of nuclear rDNA). In addition, in vitro bioassays were conducted to compare the efficacy of 10 systemic and contact fungicides. Each fungicide was evaluated at three concentrations (high, recommended, and low), estimating their effect on spore germination (SG) and mycelial growth (MG).

Results.

The isolates were identified as Thielaviopsis paradoxa. The pathogenicity tests confirmed

T. paradoxa as the causal agent of necrosis in seedlings. The systemic fungicides propiconazole, carbendazim, and tebuconazole showed complete inhibition of MG and SG starting from the lowest dose evaluated (0.45×10³, 1×10³, and 0.5×10³ ppm, respectively). The protectant fungicides copper hydroxide and captan completely inhibited SG at the lowest dose (1×10³ and 1.5×10³ ppm, respectively), although they only reached 80% inhibition of MG.

Conclusion.

T. paradoxa is reported for the first time on CEVB in Mexico. This study expands the knowledge on fungi affecting CEVB in Tabasco and provides a basis for the selection of promising fungicides, whose efficacy should be validated in subsequent field studies.

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