1/4/12, 11:44

Glyphosate affects the rhizobacterial communities in glyphosate-tolerant cotton

Los propósitos de este estudio fueron comparar las comunidades microbianas en dos suelos diferentes afectados por tratamientos con glifosato en cultivos de algodón RR, y comparar los análisis de diversidad mediante técnicas de secuenciación de ADN. Los resultados taxonómicos, filogenéticos y de diversidad demuestran claramente que el tratamiento con glifosato, en general, no parece afectar en gran medida la estructura de las comunidades bacterianas en la rizosfera de algodón, aunque su efecto relativo varía de acuerdo con la textura del suelo, lo que revela el grado relativamente bajo de agresividad de glifosato bajo las condiciones experimentales utilizadas.

Jorge Barriuso, Rafael P. Mellado

Applied Soil Ecology, 55: 20– 26 (2012)

 

The use of herbicides to kill undesirable weeds is an important element of agricultural management that can greatly alter soil characteristics. Moreover, the composition of rhizobacterial communities varies according to the soil texture. The effect of glyphosate, a post-emergence applied herbicide, on the rhizobacterial communities of genetically modified GHB614, a glyphosate-tolerant cotton, was evaluated in two different agricultural fields, one with clayey soil and the other with clayey-loam soil texture. The potential effect was monitored at two different sampling times (7 days after glyphosate application and just before crop harvesting) by high throughput DNA pyrosequencing of rhizobacterial DNA coding for the 16SrRNA hypervariable V6 region. The taxonomic analysis indicated that Proteobacteria, Acidobacteria and Actinobacteria were the more abundant taxa in both fields, although the UniFrac phylogenetic analysis differentiated one field from the other. To analyse bacterial diversity, MUSCLE alignment, DNADIST distance calculation and Mothur clustering were compared with the ESPRIT software package and both approaches gave consistent results. Thus, rhizobacterial diversity was apparently higher in the clayey soil than in the clayey-loam, judging from the OTUs and diversity index estimates. The glyphosate treatment, in general, does not seem to greatly affect the structure of bacterial communities in the cotton rhizosphere. However, the degree of recovery of the soil bacterial communities throughout plant growth was apparently less effective in the clayey-loam field than in the clayey one, strongly suggesting that recovery does indeed greatly depend on the soil textures and their associated bacterial community diversity.