Abstract
Gaeumannomyces graminis var. tritici (Ggt) is the main soilborne factor that affects wheat production around the world. Recently we reported the occurrence of six suppressive soils in monoculture areas from indigenous “Mapuche” communities, and evidenced that the suppression relied on the biotic component of those soils. Here, we compare the rhizosphere and endosphere microbial community structure (total bacteria, actinomycetes, total fungi, and ascomycetes) of wheat plants grown in suppressive and conducive soils. Our results suggested that Ggt suppression could be mediated mostly by bacterial endophytes, rather than rhizosphere microorganisms, since the community structure was similar in all suppressive soils as compared with conducive. Interestingly, we found that despite the lower incidence of take-all disease in suppressive soils, the Ggt concentration in roots was not significantly reduced in all suppressive soils compared to those growing in conducive soil. Therefore, the disease suppression is not always related to a reduction of the pathogen biomass. Furthermore, we isolated endophytic bacteria from wheat roots growing in suppressive soils. Among them we identified Serratia spp. and Enterobacter spp. able to inhibit Ggt growth in vitro. Since the disease, but not always pathogen amount, was reduced in the suppressive soils, we propose that take all disease suppressiveness is not only related to direct antagonism to the pathogen.
Highlights
Take-all disease is caused by Gaeumannomyces graminis (Sacc.) Arx et Olivier var. tritici (Walker) or Gaeumannomyces graminis var. tritici (Ggt)
Considering the unique niche that suppressive soils offer in terms of harboring specialized microbial communities to suppress Ggt, the economic and biological importance of takeall disease in wheat production, and the current technical and economical limitations for its detection, the main goals of this study were: (i) to design specific primers as a tool to evaluate by Quantitative PCR (qPCR) Ggt abundance in soil and plant samples in supressiveness studies, (ii) To determine the structure of the rhizosphere and endosphere microbial community harbored in suppressive soils, and (iii) targeted isolation of key microorganisms putatively involved in take-all disease suppression
Distance based redundancy analyses of the microbial communities based on the DGGE profiles of total bacteria, actinomycetes, total fungi and ascomycetes of the endosphere and rhizosphere of wheat plants grown in conducive and suppressive soils is shown in Figures 1, 2, respectively
Summary
Take-all disease is caused by Gaeumannomyces graminis (Sacc.) Arx et Olivier var. tritici (Walker) or Ggt. Take-all disease is caused by Gaeumannomyces graminis (Sacc.) Arx et Olivier var. Tritici (Walker) or Ggt. Take-all disease is caused by Gaeumannomyces graminis (Sacc.) Arx et Olivier var. This fungus is an ascomycete belonging to the Magnaporthe aceae family, and it affects barley, rye, and other related grasses as triticale. It is best known for its notorious negative impact on wheat production (Cook, 2003). Ggt DNA was calculated by subtracting Gga DNA amount from the calculated G. graminis total DNA This method is indirect and depends on multiple PCR reactions, significantly increasing the cost and time associated with the analysis
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