Draft genome of the fungicidal biological control agent Burkholderia anthina strain XXVI.

Burkholderia anthina XXVI is a rhizosphere bacterium isolated from a mango orchard in Mexico. This strain has a significant biological control activity against the causal agent of mango anthracnose, Colletotrichum gloeosporioides, likely through the production of siderophores and other secondary metabolites. Here, we present a draft genome sequence of B. anthina XXVI (approximately 7.7 Mb; and G + C content of 67.0%), with the aim of gaining insight into the genomic basis of antifungal modes of action, ecological success as a biological control agent, and full biosynthetic potential.

Effect of co-inoculation with mycorrhiza and rhizobia on the nodule trehalose content of different bean genotypes.

Studies on Rhizobium-legume symbiosis show that trehalose content in nodules under drought stress correlates positively with an increase in plant tolerance to this stress. Fewer reports describe trehalose accumulation in mycorrhiza where, in contrast with rhizobia, there is no flux of carbohydrates from the microsymbiont to the plant. However, the trehalose dynamics in the Mycorrhiza-Rhizobium-Legume tripartite symbiosis is unknown. The present study explores the role of this tripartite symbiosis in the trehalose content of nodules grown under contrasting moisture conditions. Three wild genotypes (P. filiformis, P. acutifolis and P. vulgaris) and two commercial genotypes of Phaseolus vulgaris (Pinto villa and Flor de Mayo) were used. Co-inoculation treatments were conducted with Glomus intraradices and a mixture of seven native rhizobial strains, and trehalose content was determined by GC/MS. The results showed a negative effect of mycorrhizal inoculation on nodule development, as mycorrhized plants showed fewer nodules and lower nodule dry weight compared to plants inoculated only with Rhizobium. Mycorrhizal colonization was also higher in plants inoculated only with Glomus as compared to plants co-inoculated with both microsymbionts. In regard to trehalose, co-inoculation negatively affects its accumulation in the nodules of each genotype tested. However, the correlation analysis showed a significantly positive correlation between mycorrhizal colonization and nodule trehalose content.

Aflatoxin synthesis in corn fields in Guanajuato, Mexico.

Aflatoxin contamination of corn is an important problem internationally, particularly in tropical and subtropical conditions that favor infection and synthesis by Aspergillus. Environmental conditions (drought) and agronomic practices i.e. N fertilization have been reported as favorable to aflatoxin synthesis in the field. This study was undertaken to investigate whether the contamination of corn commonly observed in stored conditions in this important corn producing region of Mexico known as "El Bajio" is related to infection by Aspergillus under field conditions. Results using three corn hybrids of recognized susceptibility to infection showed that corn ears artificially inoculated in the field with a toxigenic strain of Aspergillus parasiticus presented a low content of aflatoxin ranging from 13.6 to 24.7 microg Kg(-1). No significant differences were observed between the hybrids tested. Similarly, N fertilization practices, 260 Kg N ha(-1), applied at sowing did not have an effect on the extent of the contamination observed of 6.2 and 19.3 mg of aflatoxin kg(-1) in natural infected and inoculated samples with A. parasiticus NRRL 2999, respectively. Our data suggest that the cases of aflatoxin contamination of corn in this part of Mexico are not related to infection occurring during the crops growing period but most probably to poor storage conditions of corn.

Acetylene reduction activity on the root of cactaceous plants

El estado de Nuevo León tiene zonas semidesérticas con variedad de plantas cactáceas, pero con poca información sobre la entrada del nitrógeno al ecosistema, se supone que ocurre por la simboisis de Rhizhobium-leguminosas. Se exploró la actividad de reducción de acetileno (fijación biológica de N2) o ARA por bacterias asociadas a raíces de cactaceas; se determinó la relación bacteriana de la rizósfera: suelo (R:S) y se clasificaron las bacterias involucradas, para lo cual se colectaron cactáceas del municipio de Mina, Nuevo León. Hay bacterias con ARA en las raíces de Echinocereus pectinatus, E. conglomeratus, E. enneacanthus, E. blanckii, Echinocatus horizonthalonius, Coryphantha neglecta, C. macromeris, Ancistrocactus scheeri, Thelocactus bicolor y Opuntia cantabrigiensis. La relación R:S fue de 11:1 y las bacterias encontradas fueron: Enterobacter spp., Citrobacter spp., Erwinia spp; Bacillus spp, y Azospirillum lipoferum, lo que sugiere que las bacterias relacionadas con la entrada de nitrógeno al ecosistema son un grupo diverso