Extraction of eggs of Meloidogyne spp. in sodium hypochlorite (NaOCl) is a helpful procedure to assess the population levels and to obtain inoculum. In this sense, laboratory and greenhouse experiments were done to evaluate the effect of the NaOCl concentration on the viability of M. enterolobii eggs. Additionally, the objective of this investigation was to corroborate the preferable treatments to count populations in cucumber galled roots or to obtain inoculum of M. enterolobii. It was shown that the effect of the NaOCl concentration on the viability of M. enterolobii eggs is potentially detrimental. The NaOCl concentration caused a higher hatching, which in turn, resulted in non-infective larvae. Therefore, the best treatments to obtain inoculum of eggs of M. enterolobii included the 0.75% NaOCl (with 8-min stirring), 0.5% NaOCl (with stirring for 8, 12, and 16 min), and 0.3% NaOCl concentration (with stirring for 8, 12, 16, and 20 min). For a correct estimate of the egg population in roots, we show by several treatments that a concentration of 0.5% NaOCl (with stirring for 8, 12, and 16 min) and 0.75% NaOCl (with 8-min stirring) give the highest results.

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Peronospora tabacina is considered the main limiting factor in tobacco production worldwide. In Mexico, information on the genetic diversity of this pathogen is scarce; therefore, the objective of this research was to evaluate 12 microsatellites in 20 isolates collected in the states of Nayarit, Chiapas, and Veracruz. PCR amplification and sequencing of these microsatellites were performed; as well as the alignment and comparison of the sequences deposited in the GenBank database. A total of 19 isolates showed amplification for the 12 microsatellites evaluated, while in one of the isolates, the amplification of two microsatellites was not observed, it being possible to determine that P. tabacina isolates present in Nayarit, Chiapas, and Veracruz are genetically homogeneous. Regions of dinucleotides were observed, most corresponding to (GT)n repeat motifs or (TG)n variations, as well as (AC)n, (CA)n, (AT)n and (AG)n motifs. The isolates analyzed in this study can be considered products of clonal lines, therefore no genetic diversity was found in these isolates.

Cucumber (Cucumis sativus L.) is a fruit crop with high consumption worldwide. Mexico had a cucumber production of 826,485 tonnes in 2019. In December 2020, in a greenhouse in Sinaloa State, 18% of persian cucumber fruits with rot symptoms and the development of cottony white mycelia at both ends were observed similar to those described for Fusarium incarnatum (Garcia-Estrada et al., 2021). Isolation of the causal agent was carried out on PDA medium at 27°C for seven days from disinfested sections of cucumber tissues in NaOCl at 1% for one minute and then rinsed in distilled water. Morphological characterization was carried out on SNA medium, in which cultures was colorless and showed scarcely mycelia growth; however, microconidia were abundant and mainly showed clavate shaped measuring 16.6±2.2 x 5.32±1.0 μm (n=100). The morphological characteristics were similar to those described for Fusarium verticillioides (Nirenberhg, 1981). To confirm the species identity, the internal transcribed spacer (ITS) region and the actin (ACT), β-tubulin (B-tub), calmodulin (CAL), and translation elongation factor 1-α (TEF1-α) genes were amplified and sequenced from one representative isolate: FPM03. These sequences were submitted to GenBank with the accession number MZ868200 for the ITS region and MZ955274 to MZ955277 for the ACT, B-tub, CAL, and TEF1-α regions. BLASTn analysis of the sequences showed 99 to 100% identity with several F. verticillioides sequence accession numbers MG515226, KU603765, MW402311, MW402449, and MW402113, which corresponded to strains CM1, CBS 576.78, and CBS 218.76. To evaluate Koch’s postulates, ten healthy cucumber fruits were disinfected with 1% NaOCl for one min and then washed with distilled water. The fruits were inoculated with a single-spore suspension (3 × 104 conidia/mL) by spraying, as well as, five two-month-old cucumber plants. For controls, ten cucumber fruits and five plants were sprayed with sterile distilled water. All fruits were incubated in plastic bags at 25°C for four days and plants were placed under greenhouses conditions for a week. At 30 h after inoculation, all inoculated fruits showed soft rot symptoms at the fruit poles, and the development of white and cottony mycelia was observed at 48 h. Inoculated plants showed the symptoms mainly in the flower end of the fruits after three days. The symptoms observed under laboratory conditions were similar to those registered initially in the field. Samples of rotted tissues (fruit ends and flowers) from inoculated fruits were cultured on PDA medium; the resultant colonies showed similar characteristics to those obtained initially and the same pathogen was recovered. All control fruits and plants remained healthy, confirming pathogenicity. Fusarium verticillioides is primarily a maize pathogen causing stalk and ear rots globally, resulting in significant yield losses and reductions in grain quality; besides, this species produces large amounts of fumonisin B1 with high toxigenicity and is frequently found as food contaminant (Leslie and Sumerell, 2006). In addition, this pathogen was reported to affect sweet sorghum in Spain and banana in Jordan (Palmero et al., 2012; Salem et al., 2020). Recently, in Mexico, F. incarnatum was reported to cause soft rot in cucumber fruits (Garcia-Estrada et al., 2021); however, this is the first report of F. verticillioides affecting Mexican cucumber production. This information will be relevant for disease prevention and control.