Los hongos micorrizógenos arbusculares de la región de Nizanda, Oaxaca, México

Se reportan 25 especies y siete géneros de esporas de hongos micorrizógenos arbusculares (HMA) para la región de Nizanda, Oaxaca, México. Para ello, se tomaron al azar muestras de suelo, en lluvia y secas, incluyendo parcelas de cultivo de maíz, áreas de vegetación secundaria y selva baja caducifolia. Se aislaron las esporas, se identificaron y se montaron macetas de propagación. La familia Glomeraceae aportó 44% de las especies, seguida de Acaulosporaceae (24%) y Gigasporaceae (20%). Se encontraron 13 especies en el maizal, 24 en vegetación secundaria y 12 en selva baja caducifolia. De éstas, Glomus dussi, G. verruculosum, Pacispora scintillans y Scutellospora erythropa son nuevos registros para México. G. constrictum se encontró sólo en el cultivo de maíz, mientras que Acaulospora delicata, A. foveata, A. mellea, A. scrobiculata, Entrophospora infrequens, Gigaspora decipiens, Glomus claroideum, G. fulvum y G. geosporum estuvieron presentes en los tres ambientes estudiados. No se encontraron especies restringidas únicamente a la selva baja caducifolia

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

Chromosome numbers in the genus Mimosa L.: cytotaxonomic and evolutionary implications

Abstract Chromosome numbers were determined for 125 accessions of 92 taxa of Mimosa from all five of Barneby’s (Mem New York Bot Gard 65:1–835, 1991) taxonomic sections. For 69 species, 1 subspecies and 8 varieties, chromosome numbers are presented for the first time, for 6 species and 1 variety previously published data have been confirmed and for 3 species and 2 varieties different numbers were found. Results show that 74% of the accessions were diploid (2n = 2x = 26) and 26% polyploid, these mostly tetraploid (2n = 4x = 52) but with two triploid (2n = 3x = 39). These results double the number of Mimosa species for which the chromosome count is known from less than 10% previously reported to more than 20%, representing an important advance in the cytotaxonomy of this legume genus. These results together with literature data show that ca. 78% of Mimosa species are diploid. Polyploids are present in most of the taxonomic sections and in different lineages across the genus. No particular chromosome number is restricted to a given section or lineage. A possible relation between geography, species distribution, polyploidy and invasiveness was detected, however, further studies based on more accessions, especially from higher latitudes, are required before firm conclusions can be drawn