Current Insights into the Role of Rhizosphere Bacteria in Disease Suppressive Soils

Abstract

Disease suppressive soils offer effective protection to plants against infection by soil-borne pathogens, including fungi, oomycetes, bacteria, and nematodes. The specific disease suppression that operates in these soils is, in most cases, microbial in origin. Therefore, suppressive soils are considered as a rich resource for the discovery of beneficial microorganisms with novel antimicrobial and other plant protective traits. To date, several microbial genera have been proposed as key players in disease suppressiveness of soils, but the complexity of the microbial interactions as well as the underlying mechanisms and microbial traits remain elusive for most disease suppressive soils. Recent developments in next generation sequencing and other ‘omics’ technologies have provided new insights into the microbial ecology of disease suppressive soils and the identification of microbial consortia and traits involved in disease suppressiveness. Here, we review the results of recent ‘omics’-based studies on the microbial basis of disease suppressive soils, with specific emphasis on the role of rhizosphere bacteria in this intriguing microbiological phenomenon.

Linking ecology and plant pathology to unravel the importance of soil-borne fungal pathogens in species-rich grasslands

“…In general, it is thought that a larger plant diversity creates more 'niches' for soil microbes and/or promotes multiple microbial activities due to chemically more diverse exudates, thereby increasing soil suppressiveness (Gómez Expósito et al 2017;Mendes et al 2011;Schlatter et al 2017;Steinauer et al 2016). A higher microbial diversity is expected to reduce invasion of pathogens and increase antagonism in soils, thereby reducing the impact of plant pathogenic fungi (Larkin 2015;Mallon et al 2015).…”

Linking soil's volatilome to microbes and plant roots highlights the importance of microbes as emitters of belowground volatile signals

“…Bacteria are another important component of the plant root microbiome that plays a key role in plant nutrition, root development and plant health. Some bacterial strains enhance nutrient acquisition in plants (Nissinen et al, 2012;Bulgarelli et al, 2013;Vandenkoornhuyse et al, 2015;Kielak et al, 2016), support stress adaptation (Vandenkoornhuyse et al, 2015) or, like Bacillus amyloliquefaciens, suppress plant pathogens (Santhanam et al, 2015;Gómez Expósito et al, 2017;Saechow et al, 2018). Others can have deleterious or no visible effects on plants (Mansfield et al, 2012).…”

Soil properties related to suppression of Rhizoctonia solani on tobacco fields from northwest Argentina

“…In addition, the availability of varieties with genetic resistance for controlling soilborne fungi is limited, making the search for non‐chemical alternative methods necessary (Okubara et al , ). For this reason, soils with suppressive activity against different soilborne pathogens have been investigated to provide an interesting strategy for control of root diseases (Cook & Baker, ; Gómez Expósito et al , ; Schlatter et al , ).…”

“…General and specific disease suppression are two non‐mutually exclusive mechanisms proposed for characterizing suppressive soils. General suppression is related to competition for resources between all members of the soil microbial community, whereas specific suppression of one phytopathogen is explained by the activity of only part of the community, represented by specific microbial groups or antagonists (Gómez Expósito et al , ). In addition, whereas general suppression is not transferable between soils, specific suppression can be transferred by mixing 1–10% of suppressive soil into conducive soil (Schlatter et al , ).…”

“…were related to high soil suppressiveness to R. solani AG2‐2 in sugar beet (Anees et al , ). In addition, different microbial taxa of rhizospheric bacteria are associated with soil suppression of R. solani (Gómez Expósito et al , ). Among the bacterial genera implicated, Pseudomonas and Bacillus are prominent (Mendes et al , ; Yin et al , ; Donn et al , ).…”