Search

Pathogenic and genetic characterizations of 96 isolates of Macrophomina phaseolina from Mexico and other countries were carried out in order to define the pathogenic and genetic patterns of diversity and to gain insights into the pathogenic and genetic specialization in this fungus. Isolates were collected from different hosts in Mexico (23 isolates), Italy, Australia, Japan, Argentina, USA, Colombia and Brazil (73 isolates). Pathogenicity was evaluated in seeds of two Phaseolus vulgaris L. cultivars under in vitro conditions, while genotype was determined on the basis of amplified fragment-length polymorphisms (AFLPs). The most frequent pathotypes were 4095 (15 isolates) and 0 (nine isolates), while 59 isolates had a unique pathotype (61%). Cluster analysis showed two contrasting groups of isolates on the basis of pathogenicity, where one group mainly included the most aggressive isolates from Mexico and Colombia. The AFLP analysis produced 418 amplified products and 92.8% were polymorphic. Cluster analysis showed no clear association between AFLP genotype and geographical origin. When subgroups of isolates were re-analysed, we found a clear differentiation between Mexican and non-Mexican isolates. Results confirmed the significant pathogenic and genetic diversity of Macrophomina and showed a clear differentiation between Mexican isolates from all others. [ABSTRACT FROM AUTHOR]

Chromatin remodeling enzymes are important "writers", "readers" and "erasers" of the epigenetic code. These proteins are responsible for the placement, recognition, and removal of molecular marks in histone tails that trigger structural and functional changes in chromatin. This is also the case for histone deacetylases (HDACs), i.e., enzymes that remove acetyl groups from histone tails, signaling heterochromatin formation. Chromatin remodeling is necessary for cell differentiation processes in eukaryotes, and fungal pathogenesis in plants includes many adaptations to cause disease. Macrophomina phaseolina (Tassi) Goid. is a nonspecific, necrotrophic ascomycete phytopathogen that causes charcoal root disease. M. phaseolina is a frequent and highly destructive pathogen in crops such as common beans (Phaseolus vulgaris L.), particularly under both water and high temperature stresses. Here, we evaluated the effects of the classical HDAC inhibitor trichostatin A (TSA) on M. phaseolinain vitro growth and virulence. During inhibition assays, the growth of M. phaseolina in solid media, as well as the size of the microsclerotia, were reduced (p<0.05), and the colony morphology was remarkably affected. Under greenhouse experiments, treatment with TSA reduced (p<0.05) fungal virulence in common bean cv. BAT 477. Tests of LIPK, MAC1 and PMK1 gene expression during the interaction of fungi with BAT 477 revealed noticeable deregulation. Our results provide additional evidence about the role of HATs and HDACs in important biological processes of M. phaseolina., (Copyright © 2023 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.)

Aspergillus species can produce aflatoxins (AFs), which can severely affect human and animal health. The objective was to evaluate the efficacy of reducing AF contamination of a non-aflatoxigenic isolate of A. flavus experimentally coinoculated with different aflatoxigenic strains in whole plant (WP), corn silage (CS), immature grains (IG) and in culture media (CM). An L-morphotype of A. flavus (CS1) was obtained from CS in a dairy farm located in the Mexican Highland Plateau; The CS1 failed to amplify the AFs biosynthetic pathway regulatory gene (aflR). Monosporic CS1 isolates were coinoculated in WP, CS, IG and CM, together with A. flavus strains with known aflatoxigenic capacity (originating from Cuautitlán and Tamaulipas, Mexico), and native isolates from concentrate feed (CF1, CF2 and CF3) and CS (CS2, CS3). AF production was evaluated by HPLC and fungal growth rate was measured on culture media. The positive control strains and those isolated from CF produced a large average amount of AFs (15,622 ± 3952 and 12,189 ± 3311 µg/kg), whereas A. flavus strains obtained from CS produced a lower AF concentration (126 ± 25.9 µg/kg). CS1 was efficient (p < 0.01) in decreasing AF concentrations when coinoculated together with CF, CS and aflatoxigenic positive control strains (71.6−88.7, 51.0−51.1 and 63.1−71.5%) on WP, CS, IG and CM substrates (73.9−78.2, 65.1−73.7, 63.8−68.4 and 57.4−67.6%). The results suggest that the non-aflatoxigenic isolate can be an effective tool to reduce AF contamination in feed and to minimize the presence of its metabolites in raw milk and dairy products intended for human nutrition.

Despite its economic, social, biological, and cultural importance, wild forms of the genus Phaseolus are not well represented in germplasm banks, and they are at great risk due to changes in land use as well as climate change. To improve our understanding of the potential geographical distribution of wild beans ( Phaseolus spp.) from Mexico and support in situ and ex situ conservation programs, we determined the climatic adaptation ranges of 29 species and two subspecies of Phaseolus collected throughout Mexico. Based on five biotic and 117 abiotic variables obtained from different databases-WorldClim, Global-Aridity, and Global-PET-we performed principal component and cluster analyses. Germplasm was distributed among 12 climatic types from a possible 28. The general climatic ranges were as follows: 8-3,083 m above sea level; 12.07-26.96°C annual mean temperature; 10.33-202.68 mm annual precipitation; 9.33-16.56 W/m 2 of net radiation; 11.68-14.23 hr photoperiod; 0.06-1.57 aridity index; and 10-1,728 mm/month of annual potential evapotranspiration. Most descriptive variables (25) clustered species into two groups: One included germplasm from semihot climates, and the other included germplasm from temperate climates. Species clustering showed 45% to 54% coincidence with species previously grouped using molecular data. The species P. filiformis , P. purpusii , and P. maculatus were found at low-humidity locations; these species could be used to improve our understanding of the extreme aridity adaptation mechanisms used by wild beans to avoid or tolerate climate change as well as to introgress favorable alleles into new cultivars adapted to hot, dry environments.

The current understanding of the genetic diversity of the phytopathogenic fungus Ustilago maydis is limited. To determine the genetic diversity and structure of U. maydis, 48 fungal isolates were analyzed using mitochondrial simple sequence repeats (SSRs). Tumours (corn smut or 'huitlacoche') were collected from different Mexican states with diverse environmental conditions. Using bioinformatic tools, five microsatellites were identified within intergenic regions of the U. maydis mitochondrial genome. SSRMUM4 was the most polymorphic marker. The most common repeats were hexanucleotides. A total of 12 allelic variants were identified, with a mean of 2.4 alleles per locus. An estimate of the genetic diversity using analysis of molecular variance (AMOVA) revealed that the highest variance component is within states (84%), with moderate genetic differentiation between states (16%) (F ST  = 0.158). A dendrogram generated using the unweighted paired-grouping method with arithmetic averages (UPGMA) and the Bayesian analysis of population structure grouped the U. maydis isolates into two subgroups (K = 2) based on their shared SSRs.

Fungus Macrophomina phaseolina (Tassi) Goid. is the causative agent of charcoal rot disease which causes significant yield losses in major crops such as maize, sorghum, soybean and common beans in Mexico. This fungus is a facultative parasite which shows broad ability to adapt itself to stressed environments where water deficits and/or high temperature stresses commonly occur. These environmental conditions are common for most cultivable lands throughout Mexico. Here we describe some basic facts related to the etiology and epidemiology of the fungus as well as to the importance of responses to stressed environments, particularly to water deficits, based on morphology and growth traits, as well as on physiology, biochemistry and pathogenicity of fungus M. phaseolina. To conclude, we show some perspectives related to future research into the genus, which emphasize the increasing need to improve the knowledge based on the application of both traditional and biotechnological tools in order to elucidate the mechanisms of resistance to environmental stress which can be extrapolated to other useful organisms to man., (Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.)

The pink hibiscus mealybug Maconellicoccus hirsutus (Green) is a dangerous pest that damages a wide variety of agricultural, horticultural, and forestry crops. Amplified fragment length polymorphism (AFLP) fingerprints were used to characterize the genetic variation of 11 M. hirsutus populations infesting three plant species in Nayarit, Mexico. Analysis was carried out using four primers combinations, producing 590 polymorphic bands. Cluster analysis, as well as bootstrap dendrogram and nonmetric multidimensional scaling analysis, grouped M. hirsutus populations according to their host plant. The estimated F(ST) values indicated a high differentiation in M. hirsutus populations among the three host plant species. These results were also supported by a Bayesian analysis, which indicated a population clustering robustness according to their host plant. Genetic variation among populations is not caused by geographic distances, as shown by a Mantel test.