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Background: Mining deposits often contain high levels of toxic elements such as mercury (Hg) and arsenic (As) representing strong environmental hazards. The purpose of this study was the isolation for plant growth promoting bacteria (PGPBs) that can improve phytoremediation of such mine waste deposits. Methods: We isolated native soil bacteria from the rhizosphere of plants of mine waste deposits and agricultural land that was previously mine tailings from Tlalpujahua Michoacán, Mexico, and were identified by their fatty acid profile according to the MIDI Sherlock system. Plant growth promoting traits of all bacterial isolates were examined including production of 3-indoleacetic acid (IAA), siderophores, biofilm formation, and phosphate solubilization. Finally, the response of selected bacteria to mercury and arsenic was examined an in-vitro assay. Results: A total 99 bacterial strains were isolated and 48 identified, representing 34 species belonging to 23 genera. Sixty six percent of the isolates produced IAA of which Pseudomonas fluorescens TL97 produced the most. Herbaspirillum huttiense TL36 performed best in terms of phosphate solubilization and production of siderophores. In terms of biofilm formation, Bacillus atrophaeus TL76 was the best. Discussion: Most of the bacteria isolates showed high level of tolerance to the arsenic (as HAsNa2O4 and AsNaO2), whereas most isolates were susceptible to HgCl2. Three of the selected bacteria with PGP traits Herbispirillum huttiense TL36, Klebsiella oxytoca TL49 and Rhizobium radiobacter TL52 were also tolerant to high concentrations of mercury chloride, this might could be used for restoring or phytoremediating the adverse environmental conditions present in mine waste deposits. [ABSTRACT FROM AUTHOR]

La Montaña region, in southern Mexico, is characterized as a highly human-modified landscape with a rough topography, extreme poverty and structural violence. In this region, Xuajin Me'Phaa, an Indigenous non-governmental organization conformed by ca. 300 peasants, implements productive restoration projects and trades organic hibiscus (Hibiscus sabdariffa L.) as its main monetary income. Nonetheless currently, organic hibiscus yield is low compared to the potential yields in the region. Thus, it is necessary to explore alternative sustainable land management systems which enable farmers to increase hibiscus crop productivity, while halting land degradation. This study assessed the impact of six different agroecological fertilization protocols (AFPs) on hibiscus productivity planted in an alley cropping system with Calliandra houstoniana trees. The AFPs were based on the combination of three local plant amendments: C. houstoniana mulch, Mucuna pruiriens var. utilis green manure and hibiscus stover, and a commercial bio-fertilizer (Azospirillum + Rhizophagus). Simultaneously, the performance of C. houstoniana trees was assessed. The AFPs were applied in the alley cropping system and evaluated from 2016 to 2018. After 3 years, in the AFPs which included C. houstoniana mulch, hibiscus yielded significantly more (419 ± 27 kg dry calyxes ha-1 in average) than AFPs which did not include this species (264 ± 15 kg ha-1). The 18-month-old C. houstoniana trees yielded 0.6 t ha-1 of dry biomass and 1.12 t ha-1 of wooden stakes, a relatively low production. In conclusion, our results show that alley cropping with a denser arrangement of C. houstoniana trees in combination with mulching of this tree species, and use of mucuna green manure represent a promising agroforestry system for organic hibiscus production. [ABSTRACT FROM AUTHOR]

Maize is an important cereal crop worldwide. In Mexico, both hybrid and native genotypes are grown. Insect herbivory, mainly by the larvae of Spodoptera frugierda L, impose significant yield losses. Developing pest control strategies using natural enemies in an agroecological approach offers an environmentally sound alternative to minimise the input of pesticides in maize agroecosystems. Campoletis sonorensis is a native parasitoid that has shown significant control efficiency on S. frugiperda in the field, but many aspects of its ecology are largely unknown. In a controlled greenhouse experiment, we investigated the biocontrol efficacy of C. sonorensis in S. frugiperda feeding on four maize genotypes (two landraces and two hybrids). Our main results showed that maize genotype significantly affected C. sonorensis parasitism of S. frugiperda and consequently damage from herbivory. C. sonorensis diminished herbivore damage in all studied maize genotypes, and this effect was strongest in the maize hybrid PUMA. Our results show that the biocontrol efficacy of C. sonorensis against S. frugiperda is affected by the maize genotype, which should be further examined under field conditions. [ABSTRACT FROM AUTHOR]

The replacement of the most prevalent Salmonella enterica genotypes has been documented worldwide. Here we tested the hypothesis that the current prevalent sequence type ST213 of serotype Typhimurium in Mexico has a higher resistance to stressful food preservation conditions than the displaced sequence ST19. ST19 showed higher cell viability percentages than ST213 in osmotic (685 mM NaCl) and acidic (pH 3.5) stress conditions and in combination with refrigeration (4 °C) and ambient (≈22 °C) temperatures. Both genotypes showed the same poststress recovery growth. ST213 formed biofilm and filamentous cells (FCs) under stress, whereas ST19 did not. ST213 cells also showed higher motility. The capacity of ST213 to form FCs may explain its lower viability percentages when compared with ST19, i.e., ST213 cells divided less under stress conditions, but FCs had the same recovery capacity of ST19 cells. ST213 presented a higher unsaturated/saturated fatty acids ratio (0.5–0.6) than ST19 (0.2–0.5), which indicates higher membrane fluidity. The transcript levels of the rpoS gene were similar between genotypes under the experimental conditions employed. Biofilm formation, the generation of FCs, cell motility and membrane modification seem to make ST213 more resistant than ST19 to food preservation environments. • The replacement of the predominant Salmonella enterica genotype occurs worldwide. • The sequence type ST213 is displacing ST19 as the prevalent food genotype in Mexico. • Under stress, ST213 generates filamentous cells and has higher motility than ST19. • ST213 forms biofilm and modifies membrane lipids composition under stress. • ST213 resistance to food-preservation conditions partially explains ST19 replacement. [ABSTRACT FROM AUTHOR]

Phytophthora capsici is the main phytopathogen of the chili pepper crop (Capsicum annuum) and diverse commercial plants in Mexico. The limited knowledge of farmers on the presence of this pathogen in cropping areas makes it difficult to prevent and manage the disease. In order to identify and morphologically characterize isolates obtained from cucurbits and solanaceous crops with "wilt" symptoms, in Jalisco and Michoacán, Mexico, samples were collected during 2016 and 2017. The 41 P. capsici isolates obtained from diseased plants were analyzed by comparative morphology based on sexual and asexual characteristics. Were characterized 33 isolates from the C. annuum crop, six from C. pepo and two S. lycopersicum. Most isolates showed typical characteristics of P. capsici, whereas only one isolate showed terminal, globose chlamydospores (isolated from Queréndaro, Mich.). Forty heterothallic isolates were registered and only one homothallic isolate was reported. The pathogenicity of seven isolates was tested, therefore according to the results obtained, P. capsici is the main causal agent of wilt for these isolates and for seven more analyzed in a previous study, the remaining 27 are associated with the disease. Calling for the development of a strategy for integrated management of this pathogen in the Jalisco and Michoacán production areas. [ABSTRACT FROM AUTHOR]

Phytophthora blight of vegetables caused by Phytophthora capsici causes significant economic losses in production of Solanaceae and Cucurbitaceae crops in Mexico. The development of universal resistant chili pepper cultivars is challenging due to the diverse virulence phenotypes produced by P. capsici. The objective of the study was to characterize the diversity of phenotypic interactions for P. capsici isolates recovered from production fields in Michoacán, Mexico, to facilitate the development of resistant cultivars. Virulence phenotypes were characterized for 12 isolates of P. capsici using 26 Capsicum annuum New Mexico Recombinant Inbred Lines (NMRILs) in greenhouse conditions. Criollo de Morelos CM-334 and California Wonder were used as resistant and susceptible controls, respectively. Seedlings at the four to eight true leaf stage were inoculated with 10,000 zoospores per seedling and disease severity was evaluated at 20 days post-inoculation. Two of the P. capsici isolates did not infect any pepper host even though the isolate was less than a year old. The 10 virulent isolates were designated in 10 virulence phenotypes. The information generated by this study is of utmost importance for efforts of producing resistant cultivars specific forMichoacán producers. [ABSTRACT FROM AUTHOR]

Background: The dynamics of carbon (C), nitrogen (N), and phosphorus (P) in soils determine their fertility and crop growth in agroecosystems. These dynamics depend on microbial metabolism, which in turn depends on nutrient availability. Farmers typically apply either mineral or organic fertilizers to increase the availability of nutrients in soils. Phosphorus, which usually limits plant growth, is one of the most applied nutrients. Our knowledge is limited regarding how different forms of P impact the ability of microbes in soils to produce the enzymes required to release nutrients, such as C, N and P from different substrates., Methods: In this study, we used the arable layer of a calcareous soil obtained from an alfalfa cropland in Cuatro Cienegas, México, to perform an incubation experiment, where five different phosphate molecules were added as treatments substrates: three organic molecules (RNA, adenine monophosphate (AMP) and phytate) and two inorganic molecules (calcium phosphate and ammonium phosphate). Controls did not receive added phosphorus. We measured nutrient dynamics and soil microbial activity after 19 days of incubation., Results: Different P molecules affected potential microbial C mineralization (CO 2 -C) and enzyme activities, specifically in the organic treatments. P remained immobilized in the microbial biomass (Pmic) regardless of the source of P, suggesting that soil microorganisms were limited by phosphorus. Higher mineralization rates in soil amended with organic P compounds depleted dissolved organic carbon and increased nitrification. The C:N:P stoichiometry of the microbial biomass implied a change in the microbial community which affected the carbon use efficiency (CUE), threshold elemental ratio (TER), and homeostasis., Conclusion: Different organic and inorganic sources of P affect soil microbial community structure and metabolism. This modifies the dynamics of soil C, N and P. These results highlight the importance of considering the composition of organic matter and phosphate compounds used in agriculture since their impact on the microbial activity of the soil can also affect plant productivity., Competing Interests: The authors declare there are no competing interests., (©2024 Chavez-Ortiz et al.)

Objective: To evaluate the enzymatic and biocontrol capacity of native Trichoderma strains isolated from corn crops in Irapuato (state of Guanajuato) and Napízaro (state of Michoacán), Mexico., Results: Six native strains from Irapuato and Napízaro were tested, with five of them identified as T. harzianum and one as T. tomentosum. The six strains qualitatively and quantitatively showed enzyme activity for cellulase and chitinase. The best results were obtained for strains IrV6SIC7 and MichV6S2C2 with 878 IU L -1 of chitinase and 1323 IU L -1 of cellulase, respectively. All Trichoderma strains acted antagonistically toward Fusarium oxysporum f.sp. cubense race 1 (FocR1), with percentages of inhibition that ranged from 9 to 54%. In addition, the microscopic analysis allowed visualizing the mechanisms of mycoparasitism and antibiosis by either IrV6SIC7 or MichV6S2C2. The latter effects indicate that the tested native Trichoderma strains isolated from corn crops possessed enzymatic mechanisms as a strategy for biocontrolling FocR1 strains., Conclusion: The enzyme production by the Trichoderma strains represents a potential biotechnological utilization for either agricultural or industrial purposes., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Strain TE3 T , an endophytic plant growth promoting bacterium, was isolated from wheat ( Triticumturgidum subsp. durum ) sampled in the Yaqui Valley, Mexico. Biochemical, phenotypic and genotypic approaches were used to clarify the taxonomic affiliation of this strain. Based on analysis of its full-length 16S rRNA gene, strain TE3 T was assigned to the genus Bacillus (similarity ≥98.7 %). This finding was supported by morphological and metabolic characteristics, such as rod shape, strictly aerobic metabolism, spore formation, Gram-positive staining, catalase-positive activity, reduction of nitrate to nitrite, starch and casein hydrolysis, growth in presence of lysozyme and 2 % NaCl, citrate utilization, growth pH from 6.0 to 8.0, and acid and indole production from glucose and tryptophan, respectively. The whole-genome phylogenetic relationship showed that TE3 T formed an individual clade with Bacillus tequilensis KCTC 13622 T , distant from that generated by all Bacillus subtilis subspecies. The maximum values for average nucleotide identity and in silico DNA-DNA hybridization were 93.85 and 54.30 %, respectively, related to Bacillus subtilis subsp. inaquosorum KCTC 13429 T . Analysis of its fatty acid content showed the ability of strain TE3 T to bio-synthetize fatty acids that are not present in closely related Bacillus species, such as C 12 : 0 , C 12 : 0 2OH, C 12 : 0 3OH, C 17 : 0 , iso-C 17 : 0 3OH and C 18 : 1 ω9 c . These results provide evidence that strain TE3 T is a novel species of the genus Bacillus , for which the name Bacilluscabrialesii sp. nov. is proposed. The type strain of Bacilluscabrialesii is TE3 T (CM-CNRG TB54 T =CCStamb A1 T ).