Background/objective. In Tecoman, Colima, Mexico, a leaf spot (LS) disease was detected with an incidence of 92.0% in Cocos nucifera hybrid Brazilian Green Dwarf (BGD). The objective was to characterize morphologically, molecularly and biochemically the fungus associated with LS in BGD coconut palm and evaluate its susceptibility to commercial biological fungicides. Materials and methods. The isolate was characterized morphologically and molecularly. Their growth, sporulation and laccase production were evaluated using different culture media. The in vitro mycelial inhibition and mean lethal doses (LD50) of commercial biological fungicides based on antagonistic fungi (Trichoderma harzianum and T. viride), bacteria (Bacillus subtilis and B. amyloliquefaciens) and actinobacteria (Streptomyces lydicus and S. jofer) were determined. Results. Bipolaris oryzae was the associated agent of LS, it produces 25.54 and 22.17 U mg of protein-1 of laccase activity in the Sivakumar and wheat bran (WB) media. The WB medium allowed the greatest sporulation. Trichoderma harzianum inhibited B. oryzae at 100% in the four evaluated doses. B. subtilis and B. amyloliquefaciens inhibited B. oryzae at 100% at the highest tested doses (20 mL L-1). Conclusion. Bipolaris oryzae is the associated agent of LS, it produced the highest laccase activity in Sivakumar and WB culture media. The highest sporulation and daily growth rate were in WB. T. harzianum stood out over T. viride by inhibiting B. oryzae growth by 100%. B. subtilis, S. lydicus and B. amyloliquefaciens were more effective against B. oryzae in vitro compared to S. jofer.

Background/Objective. The objective was to experimentally evaluate the losses caused by PVY in the Fianna variety potato crop and, consequently, estimate the losses caused by this virus in the potato-producing area of Coahuila. Materials and Methods. Furrows of an experimental plot planted with potato seedling and seed-tuber, were mechanically inoculated with PVY at 20, 40, 60 and 80 days after emergence. The tubers produced were harvested and losses in each treatment were evaluated. Additionally, in four commercial potato fields in this same state, leaflet samples were taken at 20, 40, 60 and 80 days after the emergence, and the percentage of plants infected with PVY was evaluated by ELISA tests. Loss data from the experimental plot and incidence data from the farms were used to develop a statistical model to estimate losses caused by PVY in the Coahuila region. Results. Yield losses due to PVY in the experimental plot were 9.4% to 53%. The percentage of incidence of infected plants in commercial properties varied from 0% to 100%. The model that best fit the data obtained was Berger’s 𝑌=1/[1+𝑒 (−{𝑙n[ 𝑦0 1−𝑦0 ]+𝑟∗𝑑𝑑𝑒})]. The estimated losses in the Coahuila region in the 2022 cycle were 18%, equivalent to $19 068500. Conclusión: This information highlights the importance of using certified PVY-free seed and protecting the crop from emergence until 60 DAE.

Background/Objective. Phaseolotoxin is produced by one of the most important and studied phytopathogens in the agricultural area: Pseudomonas syringae pv. phaseolicola. This bacterium causes halo blight, a disease that devastates the bean crop. The success of P. syringae pv. phaseolicola is related to its genetic information, which allows it to synthesize deleterious metabolites for its host, such as phaseolotoxin. This research aimed to analyze the molecular basis of the mechanism of action, immunity, genetics involved in the biosynthesis of phaseolotoxin, molecular diagnostic strategies, and molecular techniques developed in Mexico to manage bean halo blight. Materials and Methods. The search and analysis of the most relevant scientific information regarding the biosynthesis of phaseolotoxin and the molecular studies of the pathogenicity and virulence factors of P. syringae pv. phaseolicola has contributed to the development of molecular strategies focused on the diagnosis and management of halo blight in beans. Results. P. syringae pv. phaseolicola produces phaseolotoxin, responsible for forming the chlorotic halo characteristic of halo blight, this toxin is an inhibitor of OCTase, an enzyme that participates in the arginine synthesis pathway in beans. The Pht and Pbo chromosomal regions contain genes involved in the synthesis and immunity of phaseolotoxin, and the expression of these genes is regulated by the GacS/GacA system and temperature. The identification of genes involved in the synthesis of pathogenicity and virulence factors, such as phaseolotoxin, has allowed the development of strategies for diagnosis and management of the disease based on DNA amplification and the use of molecular markers that facilitate the identification of bean cultivars resistant to the pathogen. Conclusion. Molecular studies have contributed to understanding how the phaseolicola pathovar produces phaseolotoxin. This information has been essential to understanding how bacteria have evolved from non-pathogenic to pathogenic variants. In addition, they provide information that allows the development of new strategies for timely diagnosis and contributes to strategies for managing halo blight.

Objective/Background. Corn tortillas are a staple food in México that have a shelf life of 1-2 days at 25 °C due to fungal growth. A natural alternative for controlling fungal growth is clove essential oil (AEC) and its major components: eugenol (E), isoeugenol (I), and eugenyl acetate (AE). Objective: to evaluate the antifungal effect of AEC on the identified fungi present in corn tortillas. Materials and Methods. One kg samples of corn tortillas were obtained from the capitals of five states of Mexico (Sonora, Nuevo León, Michoacán, Oaxaca y Yucatán). Fungi were identified by their morphology and molecular biology. Moreover, the minimum inhibitory concentration (MIC) against AEC was determined. The effect of E, I, and AE on Aspergillus niger was evaluated with the Gompertz model. Results. Two fungi were isolated from corn tortillas purchased in Nuevo León, Sonora, Yucatán, and Michoacán, and one fungus from those purchased in Oaxaca. The following fungi were identified by molecular biology in corn tortillas: Aspergillus longivesica and Curvularia spicifera from Nuevo León; Aspergillus niger and Penicillium brevicompactum from Sonora; Aspergillus sp. from Oaxaca; Mucor sp. and Aspergillus flavus from Yucatán; Penicillium herquei and Curvularia racemosus from Michoacán. The MICs were 200, 400, 800, 400, 800, 400, 800, 800, and 400 µg mL-1, respectively. AEC, E, and I at a concentration of 800 µg mL-1 delayed the growth exponential phase of Aspergillus niger, while AE did not show any effect. Conclusion. AEC could be a natural alternative for prolonging the corn tortillas′ shelf life.

Background/Objective. Tobamovirus fructirugosum species (ToBRFV) is considered a worldwide quarantine pest that limits the production of Solanum lycopersicum and Capsicum annum, currently present in three countries of the American continent. The objective of this work was to deepen in the genetic variability of ToBRFV with respect to the different isolates, the physico-molecular and symptomatic characterization, the traditional and more current methods implemented for diagnosis, the range of virus reservoir hosts, and the epidemiology. Results. ToBRFV was generated from a mutation resulting from genetic recombination with TMV, considered the main progenitor and ToMMV secondary progenitor. Phylogenetic analyses report the existence of five clades with respect to the genetic diversity of ToBRFV. The first primers for detection were designed in 2015 that encode replication, movement and capsid proteins. Serological methods can be used for preventive diagnosis, while molecular and NGS can confirm virus infection even at low concentrations in the plant. Sixteen weed families and host crops are reported from 47 countries. To achieve an effective strategy, it is necessary to reduce inoculum sources, develop compounds that inhibit mechanical transmission and develop tolerant genotypes. Conclusion. ToBRFV is distributed nationally and represents a phytosanitary risk for Mexico; the exhaustive analysis of the study of diagnostic techniques, host range, dissemination, epidemiology and control strategies, contributes to the knowledge of ToBRFV.

Background/Objective. Seed extracts from Canavalia ensiformis have shown both antiparasitic and repellent effects against pests. To evaluate the effectiveness of the extract combined with silicon dioxide nanoparticles (NPs) against Meloidogyne incognita eggs. Materials and Methods. In vitro experiments were conducted to assess the effects of C. ensiformis seed extracts, alone and combined with silicon dioxide NPs, on M. incognita juveniles hatching. 150 eggs were used, and concentrations of 0, 2, 4, 6, 8, and 10 % of the extract were applied. Additionally, concentrations of the extract at 0, 1.5, 2.0, 2.5, and 3.0 %, each combined with NP concentrations at 0.06, 0.08, 0.10, 0.12, and 0.14 %, were evaluated. Results. None of the treatments prevented more than 30 % of juveniles hatching. It was concluded that modifying the technique for obtaining C. ensiformis seed extract could have a complementary ovicidal effect; however, increasing the extract concentrations could serve as a medium for the proliferation of saprophytic fungi and other microorganisms. Conclusion. The treatments did not show significant ovicidal effects.