Dora Trejo

Interactions between arbuscular mycorrhizal fungi and Meloidogyne incognita in the ornamental plant Impatiens balsamina

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 ofnematode 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.

Efectividad de siete consorcios nativos de hongos micorrízicos arbusculares en plantas de café en condiciones de invernadero y campo

Se probo el efecto de siete consorcios de hongos micorrizicos arbusculares (HMA) aislados de fincas cafetaleras con diferente nivel de tecnologia (bajo, medio y alto) del estado de Veracruz, en el crecimiento de plantas de cafe (Coffea arabica L.) var. Garnica en condiciones de invernadero y de campo. El grado de tecnificacion influyo en la composicion de especies de HMA, a mayor tecnificacion menor numero 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 fosforo (800 mg Ca(PO4)3 L-1). A los 130 dias despues de la inoculacion (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 mas efectivos en la promocion de la altura y supervivencia de las plantas en condiciones de campo, procedieron de agroecosistemas con nivel de tecnologia medio (MI y ES), mismos que tuvieron mayor numero de especies de HMA.

Research on arbuscular mycorrhizae in Mexico: an historical synthesis and future prospects

This review analyzes the historical development and advances of the research on arbuscular mycorrhizal fungi (AMF) in Mexico, as well as the prospects for future research. AMF-research has been focused on studying both diversity and functionality in several ecosystems of Mexico, but mainly in the tropical dry and rainy ecosystems, and the agricultural systems. In Mexico, 95 species of AMF have been recorded, representing 41% of the known species worldwide. The functional effects of AMF colonization have been examined in approximately 10% of the known host plants, but greenhouse studies continue to dominate over those conducted under field conditions. Even though research to date has been at the organismic level, further effort is needed due to the high plant diversity in Mexico. Studies on AMF biomass under field conditions and more taxonomic determination are required based on morphological features, biochemical determinations (fatty acids) and molecular tools. In addition, ecophysiological and ecological in situ studies would help in understanding the relationships among AMF, soil fauna, nutrients, and host plants. The contribution of AMF to ecosystemic processes is a priority line of research that requires an integrated approach (inter- and multidisciplinary) in order to define the role of AM symbioses for biogeochemical models. The creation of a Mexican mycorrhizal research network has and will help to identify the main challenges. Generating similar research protocols, and sharing databases and experience will assist mycorrhizologists working under the diverse financial and ecological contexts that is to be found in Mexico and Latin America.

The reduction in proline buildup in mycorrhizal plants affected by nematodes

Abstract Plants stressed by pathogens activate a variety of defense mechanisms to survive. The osmoprotector amino acids, including proline, are among these defense mecha -nisms. In this work, the effects of arbuscular mycorrhizal fungi on plants infested by root-knot nematodes were evaluated with regard to the accumulation of the os-moprotectant proline. A 2x3factorial design was established with 8 treatments – with and without nematodes, with and without mycorrhizae, and with and without fertilizer application – with 4 replicates. Two weeks after inoculation with arbuscu-lar mycorrhizal fungi, the plants were infested with 4 nematode egg masses, and 8 weeks later, the plants were harvested. The inoculation with the arbuscular mycor-rhizal fungi significantly reduced the proline content, with the non-inoculated plants exhibiting a higher concentration. Neither the infestation of the nematodes nor the addition of fertilizer significantly affected the proline content. Plant height, stem diameter, leaf area, number of leaves, and fresh weight were significantly improved by the presence of the arbuscular mycorrhizal fungi. The interaction of the fungi and the fertilizer did have a significant effect for height and leaf area. The nematode infestation and the fertilization did not affect mycorrhizal colonization.