Se probó el efecto de siete consorcios de hongos micorrízicos arbusculares (HMA) aislados de fincas cafetaleras con diferente nivel de tecnología (bajo, medio y alto) del estado de Veracruz, en el crecimiento de plantas de café (Coffea arabica L.) var. Garnica en condiciones de invernadero y de campo. El grado de tecnificación influyó en la composición de especies de HMA, a mayor tecnificación menor número de especies de HMA encontradas. En condiciones de invernadero, los consorcios incrementaron la altura en un 91 % con respecto al testigo absoluto y al testigo fertilizado con fósforo (800 mg Ca(PO 4) 3 L-1). A los 130 días después de la inoculación (DDI), el mejor consorcio fue La Estanzuela (ES). En condiciones de campo, a los 290 DDI, las plantas inoculadas con los consorcios ES, Miradores (MI), y Paso Grande (PG) tuvieron mayor supervivencia (> 80 %). Los consorcios más efectivos en la promoción de la altura y supervivencia de las plantas en condiciones de campo, procedieron de agroecosistemas con nivel de tecnología medio (MI y ES), mismos que tuvieron mayor número de especies de HMA.

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Long-term successional dynamics of an inoculum of arbuscular mycorrhizal fungi (AMF) associated with the maize rhizosphere (from traditionally managed agroecosystems in Los Tuxtlas, Veracruz, Mexico), was followed in Bracchiaria comata trap cultures for almost eight years. The results indicate that AMF diversity is lost following long-term subculturing of a single plant host species. Only the dominant species, Claroideoglomus etunicatum, persisted in pot cultures after 13 cycles. The absence of other morphotypes was demonstrated by an 18S rDNA survey, which confirmed that the sequences present solely belonged to C. etunicatum. Members of Diversisporales were the first to decrease in diversity, and the most persistent species belonged to Glomerales.

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The arbuscular mycorrhizal fungal diversity in Mexico has not been intensively studied. Although some studies have reported the presence of 29 % of the reported species in the world, the knowledge regarding their functional diversity is poor. The aim of this study was to evaluate the impact of the disturbance on arbuscular mycorrhizal fungi (AMF) functional diversity. Three sites at the Biosphere Reserve Los Tuxtlas in the state of Veracruz were selected for this study, according to the disturbance gradient and the land use: López Mateos (LM), San Fernando (SF), and Venustiano Carranza (VC) (with low, medium and high disturbance, respectively). The land use in each site includes milpa and pasture. High percentages of root colonization, spore abundance and spore viability were found on LM soils. Additionally, 100 % of the pasture soils have a high mycorrhizal infective potential (MIP). In addition, the fungi consortiums coming from that site promote the highest mycorrhizal growth response (MGR), with increases ranging from 74.1 to 194.6 % over the control treatment. SF soils had high percentages of root colonization and spore viability, whereas only 20 % of these soils had a high MIP, and their MGR promoted increases ranged from 14.6 to 120.4 % over the control. Soils from VC had the lowest percentages of root colonization and spore viability. Only 10 % of the soils had high MIP, and their MGR was not better than the control. These results indicate that the soil disturbance or use changes negatively affect the functionality of AMF.

Biocontrol traits of arbuscular mycorrhizal fungi (AMF), in terms of single and mixed species inoculum, against the root knot nematode Meloidogyne incongita in Impatiens balsamina L., were examined with and without mineral fertilization in a greenhouse pot experiment. At harvest, 60 days after sowing, general plant growth parameters and plant defense response in terms of antioxidant activity and content of phenolic compounds in roots and leaves were measured. Also AMF root colonization and abundance of nematode root-knots were determined. Mineral fertilization increased all plant growth parameters measured, which coincided with an increased disease development caused by M. incognita. Inoculation with AMF mitigated the observed plant growth reduction caused by M.incognita, though, higher abundance of M. incognita root knots was found in mycorrhizal plants. Plant defense responses in terms of antioxidant activity and content of phenolic compounds did not seem to be linked to the observed biocontrol traits of AMF against M. incognita. However, roots inoculated with a consortium of AMF, which presented less nematode root knots than roots with the single species inoculum, had the highest level of phenolic compounds. The results from the present study suggest that AMF induce tolerance in I. balsamina against the root knot nematode M. incognita.

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