Comparison of rhizobacterial community composition in soil suppressive or conducive to tobacco black root rot disease

Abstract

Work on soils suppressive to Thielaviopsis basicola-mediated tobacco black root rot has focused on antagonistic pseudomonads to date. The role of non-Pseudomonas rhizosphere populations has been neglected, and whether they differ in black root rot-suppressive versus -conducive soils is unknown. To assess this possibility, tobacco was grown in a suppressive and a conducive soil of similar physicochemical properties, and rhizobacterial community composition was compared using a 16S rRNA taxonomic microarray. The microarray contains 1033 probes and targets 19 bacterial phyla. Among them, 398 probes were designed for Proteobacteria, Firmicutes, Actinomycetes, Cyanobacteria and Bacteroidetes genera/species known to include strains relevant for plant protection or plant growth promotion. Hierarchical clustering as well as principal component analysis of microarray data discriminated clearly between black root rot-suppressive and -conducive soils. In contrast, T. basicola inoculation had no impact on rhizobacterial community composition. In addition to fluorescent Pseudomonas, the taxa Azospirillum, Gluconacetobacter, Burkholderia, Comamonas and Sphingomonadaceae, which are known to comprise strains with plant-beneficial properties, were more prevalent in the suppressive soil. Mycobacterium, Bradyrhizobium, Rhodobacteraceae, Rhodospirillum and others were more prevalent in the conducive soil. For selected taxa, microarray results were largely corroborated by quantitative PCR and cloning/sequencing. In conclusion, this work identified novel bacterial taxa that could serve as indicators of disease suppressiveness in soil-quality assessments, and it extends the range of bacterial taxa hypothesized to participate in black root rot suppression.

Prevalence and Pattern of Traditional and Complementary Alternative Medicine Use in Diabetic Patients in Dubai, UAE

“…This result was consistent with another study conducted in the Emirate of Ajman in the UAE, where 71.8% of the TCAM use was not through physician prescription or supervision [10]. Similar finding was seen in the study conducted in Palestine.…”

“…Similar result was observed in Palestine where 45.7% reported using TCAM to slow the progression of diabetes [13]. Nonetheless, this study in addition to others showed that majority of TCAM users were satisfied with the results [2,3,10,11,13]. Despite that, special attention has to be given to those experiencing diabetes side effects.…”

Role of Bacterial Communities in the Natural Suppression of Rhizoctonia solani Bare Patch Disease of Wheat (Triticum aestivum L.)

“…This indicated that our cycling experiments in the greenhouse could duplicate some taxonomic shifts in bacteria that operate at the field level. Kyselková et al (28) found that taxa of Pseudomonas and Bacteroidetes were higher in soil suppressive to tobacco black rot caused by Thielaviopsis basicola when they used a microarray based on 16S RNA, similar to our results. We further demonstrated that Chryseobacterium and Pseudomonas exhibited inhibitory activities against R. solani in vitro or reduced Rhizoctonia disease in inoculated natural soils (Table 5 and 6).…”

“…The diversity of soil microbial communities is important for the capacity of a soil to suppress soilborne plant diseases (26,27). In disease-suppressive soils, some of the indigenous microorganisms protect susceptible crops from certain phytopathogens (28). Some isolates of Mitsuaria and Burkholderia inhibited fungal and oomycete growth in vitro and reduced disease severity in infected tomato (Solanum lycopersicum L.) and soybean (Glycine max L.) seedlings (29).…”

Oligonucleotide microarray methodology for taxonomic and functional monitoringof microbial community composition

“…Bacillus spp. (liu et al 2001), Rhodocyclales (loy et al 2005), Alphaproteobacteria (Sanguin et al 2006a), or attempt to cover most bacterial phyla (Brodie et al 2006, Kyselková et al 2009). …”