First Look Into the Ambrosia Beetle-Fungus Symbiosis Present in Commercial Avocado Orchards in Michoacán, Mexico.

Most beetle-fungus symbioses do not represent a threat to agricultural and natural ecosystems; however, a few beetles are able to inoculate healthy hosts with disease-causing fungal symbionts. Here, we report the putative nutritional symbionts associated with five native species of ambrosia beetles colonizing commercial avocado trees in four locations in Michoacán. Knowing which beetles are present in the commercial orchards and the surrounding areas, as well as their fungal associates, is imperative for developing a realistic risk assessment and an effective monitoring system that allows for timely management actions. Phylogenetic analysis revealed five potentially new, previously undescribed species of Raffaelea, and three known species (R. arxi, R. brunnea, R. fusca). The genus Raffaelea was recovered from all the beetle species and across the different locations. Raffaelea lauricola (RL), which causes a deadly vascular fungal disease known as laurel wilt (LW) in Lauraceae species, including avocado, was not recovered. This study points to the imminent danger of native ambrosia beetles spreading RL if the pathogen is introduced to Mexico's avocado orchards or natural areas given that these beetles are associated with Raffaelea species and that lateral transfer of RL among ambrosia beetles in Florida suggests that the likelihood of this phenomenon increases when partners are phylogenetically close. Therefore, this study provides important information about the potential vectors of RL in Mexico and other avocado producing regions. Confirming beetle-fungal identities in these areas is especially important given the serious threat laurel wilt disease represents to the avocado industry in Mexico.

A Novel Disease of Big-Leaf Mahogany Caused by Two Fusarium Species in Mexico.

Big-leaf mahogany (Swietenia macrophylla) is valued for its high-quality wood and use in urban landscapes in Mexico. During surveys of mango-producing areas in the central western region of Mexico, symptoms of malformation, the most important disease of mango in the area, were observed on big-leaf mahogany trees. The objectives of this research were to describe this new disease and determine its cause. Symptoms on big-leaf mahogany at four sites in Michoacán, Mexico resembled those of the vegetative phase of mango malformation, including compact, bunched growth of apical and lateral buds, with greatly shortened internodes and small leaves that curved back toward the supporting stem. Of 163 isolates that were recovered from symptomatic tissues, most were identified as Fusarium pseudocircinatum (n = 121) and F. mexicanum (n = 39) using molecular systematic data; two isolates represented unnamed phylospecies within the F. incarnatum-equiseti species complex (FIESC 20-d and FIESC 37-a) and another was in the F. solani species complex (FSSC 25-m). However, only F. mexicanum and F. pseudocircinatum induced malformation symptoms on 14-day-old seedlings of big-leaf mahogany. The results indicate that F. mexicanum and F. pseudocircinatum, previously reported in Mexico as causal agents of mango malformation disease, also affect big-leaf mahogany. This is the first report of this new disease and the first time that F. mexicanum was shown to affect a host other than mango.

RAPD discloses high molecular diversity of Mycobacterium tuberculosis from Michoacan, Mexico.

Random amplified polymorphism DNA (RAPD) is an easy, inexpensive technique for the characterization of pathogens in low-income countries. In this study we used RAPD to assess the genetic diversity of a small collection of isolates of mycobacteria from the Mexican state of Michoacan. In contrast with the low annual tuberculosis incidence in Michoacan relative to the national average, we found a high molecular diversity value suggesting high population diversity of M. tuberculosis in the studied region. Our findings justify further typing efforts with other molecular tools such as MIRU-VNTR and spoligotyping.

Genetic diversity among Mycobacterium tuberculosis isolates from Mexican patients.

Forty-six isolates of the Mycobacterium tuberculosis complex were typified by PCR of the IS6110 region and by Mycobacterium bovis specific primers JB21/JB22. Isolate MVG01 was typified as M. bovis, being the first record of a case of human tuberculosis caused by this species in Mexico. RAPD-PCR was used to describe the genetic diversity of the remaining 45 M. tuberculosis complex isolates. The corrected genotypic diversity value calculated for the analyzed population was 0.96, the estimated mean gene diversity was 0.235, and the corrected Shannon-Weiner index was 2.15. All allele-loci combinations generated showed significant linkage disequilibria. The distribution of genetic variation was analyzed both by the unweighted pair group method with arithmetic averages clustering and by principal coordinates analysis. Unweighted pair group method with arithmetic averages clustering resulted in a tree with four main clusters and one unclustered strain (MVG20), the principal coordinates analysis strain distribution pattern being consistent with this grouping. The obtained results suggest that the studied isolates belong to a clonal population having significant genetic diversity. Our genetic diversity results are comparable with those reported for other populations of M. tuberculosis, although only three RAPD primers were used.

Determination of alpha- and beta-amanitin in clinical urine samples by Capillary Zone Electrophoresis.

Amanitins are toxins found in species of the mushroom genera Amanita, Lepiota and Galerina. Intoxication after ingestion of these mushrooms can be fatal with an estimated 20% of mortality rate. An early diagnosis is necessary in order to avoid invasive and expensive therapy and to improve patient's prognosis. In this paper, a Capillary Zone Electrophoresis method was developed and validated to determine alpha- and beta-amanitin in urine in less than 7 min using 5 mM, pH 10 borate buffer as background electrolyte. The separation conditions were: capillary: 75 microm I.D., 41 cm effective length, 48 cm total length, 25 degrees C, 20 KV and PDA detection at 214 nm. Sample treatment for analysis only required urine dilution in background electrolyte. The method was validated following established criteria and was found to be selective, linear in the range 5-100 ng/ml. Intra- and inter-day precision and accuracy were within required limits. Limit of detection (LOD) and limit of quantification (LOQ) were 1.5 and 5 ng/ml, respectively. Eight urine samples from suspected cases of intoxication with amanitins were analyzed after 2 years of storage at -20 degrees C, and beta-amanitin was determined in two samples with concentrations of 53 and 65 ng/ml, respectively. The method here described includes the use of non-aggressive reagents to the capillary or the system and is the first Capillary Electrophoresis method used to determine amanitins in clinical samples.