Bacillus amyloliquefaciens BNM122, a potential microbial biocontrol agent applied on soybean seeds, causes a minor impact on non-target microorganisms

CORREA, OLGA S.; MONTECCHIA, MARCELA S.; BERTI, MARÍA F.; FERNÁNDEZ FERRARI, MARÍA C.; PUCHEU, NORMA L.; KERBER, NORMA L.; GARCÍA, AUGUSTO F.

APPLIED SOIL ECOLOGY

Springer

Año: 2009 vol. 41 p. 185 - 194

0929-1393

AbstractThe increase in soybean productivity has contributed to agreater use of agrochemicals,which cause major problems, such as soil and water pollution and reduction of biodiversity,and have a negative impact on non-target species. The development of microbial biocontrolagents for soybean diseases can help to reduce pesticide abuse.Bacillus amyloliquefaciens BNM122 is a potential microbial biocontrol agent able to control the damping-off caused by Rhizoctonia solani when inoculated in soybean seeds, both in a plant growth chamber  and in a greenhouse. In this study, we report the effect of soybean seed treatments with strain BNM122 or with two fungicides (thiram and  carbendazim)on the structure and function of the bacterial community that colonizes thes oybean rhizosphere. Also, soybean root nodulation by  Bradyrhizobium japonicum, mycorrhization by arbuscular mycorrhizal fungi and plant growth were evaluated. We used the r and K strategist concept to evaluate the ecophysiological structure of the culturable bacterial community, community-level physiological profiles (CLPP) in Biolog TM EcoPlates to study bacterial functionality, and the patterns of 16SRNA genes amplified by PCR and separated by denaturing gradient gel electrophoresis (PCR-DGGE) to assess the genetic structure of the bacterial community.Neither the ecophysiological structure nor the physiological profiles of the soybean rhizosphere bacterial community showed important changes after seed inoculation with strain BNM122. On the contrary, seed treatment with fungicides increased the proportions of r strategists and altered the metabolic profiles of ther hizosphere culturable bacterial community. The genetic structure of the rhizosphere bacterial community did not show perceptible changes between treated and non-treated seeds. Regarding the bacterial andfungal symbioses, seed treatments did not affect soybean nodulation, whereas soybean mycorrhization significantly decreased (P< 0.05) in plants obtained with seeds treated with strain BNM122 or with the fungicides. However, a higher negative  effectwas observed in plants which seeds were treated with the fungicides. Plant growth was  not affected by seed treatments.