Institute Fitosanidad

Montecillo, Mexico

Institute Fitosanidad

Montecillo, Mexico
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Sanchez-Garcia B.M.,Roque Institute of Technology | Espinosa-Huerta E.,Institute Fitosanidad | Villordo-Pineda E.,Polytechnic University of Guanajuato | Rodriguez-Guerra R.,Instituto Nacional de Investigaciones Nucleares | Mora-Aviles M.A.,Polytechnic University of Guanajuato
Agrociencia | Year: 2017

Trichoderma spp. is a fungus of the Ascomycota division with great potential to control diseases in economically important crops. This antagonistic fungus inhibits the growth of phytopathogenic microorganisms, including those responsible for root diseases, such as Rhizoctonia spp. and Fusarium spp. The objective of this study was to identify Trichoderma species and to describe their in vitro antagonistic activity in pathogenic strains of Rhizoctonia solani, F. oxysporum, F. verticillioides and F. solani, with different virulence determined based on pathogenicity tests in bean plants (Phaseolus vulgaris L.) cv. Montcalm. The hypothesis was that the identification and antagonistic description of Trichoderma species against pathogenic fungi defines their biological control efficiency. The experimental design was completely random, with at least three repetitions. The molecular identification of Trichoderma spp. was done through ITS1 and ITS2 regions, separated by the 5.8S ribosomal RNA gene (ITS, Internal Transcribed Spacer). The antagonism was evaluated using the modified cellophane method and dual cultures to estimate the percentage of radial growth inhibition (PRGI). Seven Trichoderma strains identified using molecular techniques showed 95-100 % identity to T. harzianum and T. asperellum. Trichoderma strains showed high antagonistic capacity with 73.1 to 76.4 mean PRGI values in pathogenic strains, suggesting an antibiosis effect (77.6 PRGI) and different hyphal interaction types. Antagonistic strains were statistically similar for pathogen growth and development inhibition; however, T. asperellum's antagonistic values were higher than T. harzianum's with regard to all pathogenic strains, even R. solani, which was the most aggressive pathogen for cv. Montcalm (mean value: 7.0). The antagonistic effect of Trichoderma strains on phytopathogenic fungi was determined with in vitro tests and corroborated with in vivo bioassays with similar inhibition percentages.

Flota-Banuelos C.,Tizimín Institute of Technology | Imelda Martinez M.,Institute Ecologia | Lopez-Collado J.,Campus Veracruz | Mendoza M.V.,Campus Veracruz | And 2 more authors.
Revista de Biologia Tropical | Year: 2013

The spatial and temporal distribution of gastrointestinal nematodes of cattle has been little studied in Mexico. Previous studies have described periods of higher larval presence, vertical and horizontal migration in grasslands, and the frequency of adult nematodes; as well as the effect of pasture trichomes on the migration and survival of Haemonchus larvae. The aim of this study was to determine the time-space layout and spread of gastrointestinal nematode larvae on pasture, and to estimate the effect of ivermectin applied to cattle on the time-dependent abundance of their eggs in a ranch in Veracruz. To determine the spatio-temporal arrangement, monthly morning grass samples were obtained from 30 sampling points from July 2008 to June 2009. Third stage larvae (L3) from each point were counted, and aggregation patterns were estimated through variance/mean and negative binomial K indices. Additionally, the number of eggs per gram in cattle feces was determined, from samples with (CI) and without ivermectin (SI), using standard techniques. A total of 20 276L3 larvae were recovered in the pasture, of which an 80% corresponded to Haemonchus contortus. The highest nematode density with more than 5 000L3/kgDM was detected in October 2008, and the lowest in February and March 2009. The L3 showed an aggregated spatial pattern of varying intensity throughout the year. The number of eggs in the stool was not reduced with the ivermectin application to cattle, which suggested a failure of control. However, the highest parasite loads were observed from July to November 2008. We concluded that the application of ivermectin was not effective to control nematodes eggs, and that L3 populations fluctuated on pasture for ten months, providing an infection source to grazing animals afterwards.

Ascunce M.S.,U.S. Department of Agriculture | Ascunce M.S.,University of Florida | Valles S.M.,U.S. Department of Agriculture | Oi D.H.,U.S. Department of Agriculture | And 6 more authors.
Journal of Invertebrate Pathology | Year: 2010

Kneallhazia solenopsae is a pathogenic microsporidium that infects the fire ants Solenopsis invicta and Solenopsis richteri in South America and the USA. In this study, we analyzed the prevalence and molecular diversity of K. solenopsae in fire ants from North and South America. We report the first empirical evidence of K. solenopsae infections in the tropical fire ant, Solenopsis geminata, and S. geminata×. Solenopsis xyloni hybrids, revealing an expanded host range for this microsporidium. We also analyzed the molecular diversity at the 16S ribosomal RNA gene in K. solenopsae from the ant hosts S. invicta, S. richteri, S. geminata and S. geminata×. S. xyloni hybrids from North America, Argentina and Brazil. We found 22 16S haplotypes. One of these haplotypes (WD_1) appears to be widely distributed, and is found in S. invicta from the USA and S. geminata from southern Mexico. Phylogenetic analyses of 16S sequences revealed that K. solenopsae haplotypes fall into one of two major clades that are differentiated by 2-3%. In some cases, multiple K. solenopsae haplotypes per colony were found, suggesting either an incomplete homogenization among gene copies within the 16S gene cluster or multiple K. solenopsae variants simultaneously infecting host colonies. © 2010 Elsevier Inc.

Chino-Cantor A.,Autonomous University of Guerrero | Sanchez-Arroyo H.,Institute Fitosanidad | Ortega-Arenas L.D.,Institute Fitosanidad | Castro-Hernandez E.,Autonomous University of Guerrero
Southwestern Entomologist | Year: 2014

With the aim to provide bases to define a regional management strategy of insecticides, the susceptibility of populations of Aedes aegypti from three regions of Guerrero, Mexico, to the insecticides malathion, temefos, chlorpyrifos, pirimiphosmetil, permethrin, lambda-cyhalothrin, propoxur, and spinosin was determinated, using the New Orleans population as a reference. Commercial and technical-grade insecticides were evaluated by residual application in larvae of early fourth instar according to the methodology proposed by the World Health Organization. The mortality was recorded 24 hours after application. Probit analysis was used to determinate the response lines log dose-mortality, LC50 values and the resistant factor for each product. The results indicate that the three populations of A. aegypti were resistant to the insecticide lambda cyhalothrin, and the populations from Acapulco and Costa Chica were moderately resistant to pirimiphos methyl. In contrast, the three field populations were susceptible to malathion, temephos, chlorpyrifos, permethrin, propoxur, and spinosin. However, although some products were found to be effective, it is recommended to use them in rotation combining different modes of action and in conjunction with other alternatives, as removal of breeding sites, to preserve the life of the authorized insecticides. This study provides useful reference information for the development and implementation of strategies for managing and monitoring local insecticide resistance of A. aegypti in Guerrero, Mexico.

Tovar-Pedraza J.M.,Institute Fitosanidad | Ayala-Escobar V.,Institute Fitosanidad | Segura-Leon O.L.,Institute Fitosanidad
Australasian Plant Disease Notes | Year: 2013

During the spring of 2010, two fungal isolates were obtained from apricot tissues with symptoms of shot-hole in the State of Mexico, Mexico. Based on morphology, cultural features, rDNA ITS sequence and the fulfilment of Koch's postulates on apricot leaves and fruits, the causal agent was identified as Thyrostroma carpophilum. This is the first report of T. carpophilum causing apricot shot-hole in Mexico. © 2013 Australasian Plant Pathology Society Inc.

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