Arbuscular mycorrhizal fungi in heavy metal highly polluted soil in the Riachuelo river basin Arbuscular mycorrhizal fungi in heavy metal highly polluted soil / Hongos formadores de micorrizas arbusculares en el suelo extremadamente contaminado con metales pesados de la cuenca del río Riachuelo

Abstract The Riachuelo river basin (RRB) is considered one of the most polluted environments in the world. Knowledge of arbuscular mycorrhizal fungi (AMF) adapted to this extremely polluted environment is important for the establishment of future soil restoration projects. This work aims to make a first list of AMF species present on the RRB. Soil and root samples were randomly taken in an area of approximately 1500 m2, mycorrhization percentages were evaluated. AMF species were detected by molecular and morphological techniques. Sixteen AMF morphological species and 64 molecular species were reported in this work. Dominikia iranica, Funneliformis constrictum, Funneliformis mosseae, Rhizophagus intraradices, Rhizophagus irregularis and Septoglomus viscosum were detected by both techniques while Claroideoglomus sp. was only detected by pyrosequencing. The list of species reported in this work represents the first description of the RRB AMF community.

Resumen La cuenca del río Riachuelo (CRR) es considerada uno de los ambientes más contaminados del mundo. Conocer los hongos formadores de micorrizas arbusculares (HFMA) adaptados a este ambiente extremadamente contaminado es importante para el establecimiento de futuros proyectos de restauración de suelos. Este trabajo se propuso hacer una primera lista de especies de HFMA presentes en la CRR. Se tomaron muestras de suelo y raíces al azar en un área de aproximadamente 1500 m2 y se evaluaron los porcentajes de micorrización. La identificación de especies de HFMA se basó en técnicas moleculares y morfológicas. Se detectaron 16 especies morfológicas y 64 especies moleculares de HFMA. Dominikia iranica, Funneliformis constrictum, Funneliformis mosseae, Rhizophagus intraradices, Rhizophagus irregularis y Septoglomus viscosum se detectaron mediante ambas técnicas, mientras que Claroideoglomus sp. solo fue detectado por pirosecuenciación. La lista de especies reportada en este trabajo representa la primera descripción de la comunidad de HFMA de la CRR.

Growth dynamics of geographically different arbuscular mycorrhizal fungal isolates belonging to the 'Rhizophagus clade' under monoxenic conditions.

The growth dynamics of extraradical mycelium and spore formation of 14 "Rhizophagus" isolates from different sites in Argentina were evaluated under monoxenic conditions. A modified Gompertz model was used to characterize the development of mycelium and spores for each isolate under the same conditions. The lag time, maximal growth rate and total quantity of both extraradical hyphae and spores were determined. Wide variability among isolates was detected, and all growth parameters were significantly altered by fungal isolate. Discriminant analysis differentiated isolates primarily based on the extent of extraradical hyphae produced, yet such differences did not conclusively correspond to phylogenetic relationships among closely related isolates based on partial SSU sequences. Given that the "Rhizophagus" isolates were grown under controlled conditions for many generations, the expression of phenotypic variability could be attributed to genetic differences that are not completely resolved by phylogenetic analysis employing the small ribosomal gene.

Continuous and long-term monoxenic culture of the arbuscular mycorrhizal fungus Gigaspora decipiens in root organ culture.

Establishment of arbuscular mycorrhizal (AM) germplasm collections is complex because of the obligate biotrophic nature of AM fungi. Only a few AM species are routinely maintained in monoxenic culture with Ri T-DNA transformed roots as host. Incorporation of new AM species into this culture system is important for molecular, physiological, and taxonomical studies. Here we report for the first time the successful monoxenic culture of Gigaspora decipiens (JA2 strain) with transformed carrot (Daucus carota) roots. In vitro cultures were established from field-collected spores; sub-culture of newly in vitro formed spores was established over five successive generations for a period of 6 y. Although initial culture of field-collected spores was difficult successive sub-cultures appeared to be adapted to the in vitro growing conditions. The JA2 strain of G. decipiens completed its life cycle while maintaining its morphological characteristics, stability, and propagule viability under the monoxenic conditions over several generations. This stable and homogeneous monoxenic material obtained for G. decipiens is part of the Banco de Glomeromycota In Vitro (BGIV, http://www.bgiv.com.ar), and could facilitate morphological, physiological, and molecular analysis of this AM species.