Monoculture and Soilborne Plant Pathogens

Shipton, P. J.

doi:10.1146/annurev.py.15.090177.002131

Cited by 125 publications

(61 citation statements)

References 21 publications

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“…As has been noted previously, the development of take-all decline may be influenced by multiple attributes of the agro-ecosystem [44,52]. In this study, it was rare to recover phlD + isolates from the rhizosphere of wheat grown in WVC-SS orchard soil, and populations of 2,4-DAPG-producing fluorescent pseudomonads did not approach the threshold densities (>10 5 cfu g )1 root) necessary to achieve take-all decline [41].…”

Section: Discussionsupporting

confidence: 49%

Wheat Cultivar-Specific Selection of 2,4-Diacetylphloroglucinol-Producing Fluorescent Pseudomonas Species from Resident Soil Populations

Mazzola¹,

2004

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An emerging body of evidence indicates a role for plant genotype as a determinant of the species and genetic composition of the saprophytic microbial community resident to the rhizosphere. In this study, experiments were conducted to determine the capacity of five different wheat cultivars to enhance resident populations and support introduced strains of 2,4-diacetylphloroglucinol (2,4-DAPG)-producing fluorescent pseudomonads, a group of bacteria known to provide biological control of several soilborne diseases. When soils were cropped with three successive 28-day growth cycles of wheat, the 2,4-DAPG-producing strains were consistently recovered from the rhizosphere of the cultivar Lewjain, and commonly were present at populations higher than those recovered from other wheat cultivars. Based on restriction fragment length polymorphism and sequence analyses of phlD, a key gene involved in 2,4-DAPG production, two previously undefined phlD+ genotypes, referred to as genotypes PfZ and PfY, were discovered. Wheat cultivar Lewjain was the primary source of genotype PfY while cultivar Penawawa yielded the majority of genotype PfZ. Based on 16S rDNA sequence analysis, both new phlD genotypes were classified as P. fluorescens. Comparison of the rhizosphere competence of 2,4-DAPG-producing P. fluorescens Q2-87 (genotype B) and P. fluorescens LR3-A28 (genotype PfY) showed that both strains persisted at similar populations in the rhizosphere of all cultivars tested over a 30 day period when introduced as a seed inoculant. However, when strain LR3-A28 was applied as a soil inoculant, this strain was recovered at higher populations from the rhizosphere of wheat cultivar Lewjain than from the rhizospheres of two other cultivars. No cultivar effects were shown for strain Q2-87. Collectively, these results add further to evidence indicating a degree of specificity in interactions between plant cultivars and specific members of the saprophytic microbial community. Furthermore, as 2,4-DAPG-producing fluorescent Pseudomonas spp. have a central role in the spontaneous reduction in severity of take-all disease of wheat in response to continuous wheat monoculture, we postulate that the use of specific cultivars, such as Lewjain, which possess a superior capacity to enhance resident soil populations of these bacteria may have potential to reduce the length of the monoculture period required to induce natural suppressiveness of soils toward this disease.

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Section: Discussionsupporting

confidence: 49%

Wheat Cultivar-Specific Selection of 2,4-Diacetylphloroglucinol-Producing Fluorescent Pseudomonas Species from Resident Soil Populations

Mazzola¹,

2004

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“…The effects may be attributed to a larger residual soil N from the former system compared to the latter (Bagayoko et al, 1996). These effects obviously derive from the larger amounts of above-and belowground biomass/residues returned to the plots after harvesting the beans and perhaps also because of changes in microbial activities after legumes (Shipton, 1977;Turco et al, 1990). The same effect is sometimes referred to as allowing subsequent crops to access more P (Johnson et al, 1992;Bainville et al, 2005).…”

Section: The Productivity Of Maize-based Systems Under Different Pracmentioning

confidence: 99%

Profitability of diammonium phosphate use in bush and climbing bean-maize rotations in smallholder farms of Central Burundi

Niyuhire

Pypers

Vanlauwe

et al. 2017

Field Crops Research

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A B S T R A C TSoil fertility decline is a major constraint to bean (Phaseolus vulgaris L.) and maize (Zea mays) production in the Central Highlands of Burundi. Nutrient sources, specifically fertilizers, are paramount to increasing the production in the regions. Hence, improving fertilizer use efficiency is considered as a key factor towards sustainable intensification. The use of grain legumes with low harvest indices, such as climbing beans, are assumed to improve soil fertility and fertilizer use efficiency. This study compares the rotational effects of bush and climbing bean varieties on maize and evaluates the profitability of diammonium phosphate (DAP, fertilizer in the bean-maize rotations in 59 smallholder farms of Mutaho district, Gitega Province in Central Burundi. The application of DAP fertilizer significantly increased the grain yields by 14% and 21% for bush and climbing beans, respectively (P < 0.001). Positive effects of bean varieties were large for about 80% of the farmers. Climbing beans in general yielded more than bush beans for about two thirds of the farmers and fertilizer effects were positive. In the bean-maize rotations, the fertilizer induced on average a yield increase of 8% and 22% for maize following bush and climbing beans, respectively. Maize grain yields were significantly (P < 0.001) higher following climbing beans than following bush beans. The value cost ratio (VCR) more than doubled compared with the common practice (bush bean-maize rotation). Variation was substantial, and for approximately 67% of the farmers, DAP application was profitable (VCR > 2 $ $ −1 ) in a climbing bean-maize rotation while 45% of the farmers in a bush bean-maize rotation. Regression tree analysis showed that targeting fertilizer use to soils with higher C and clay content, and ensuring timely planting are the predominant factors to ensure fertilizer response and profitable returns. This study confirms the need for integrated soil fertility management (ISFM), and that a combination of judicious fertilizer use, an improved grain legume (climbing bean) and adjustment to local conditions (targeting to responsive soils) maximizes economic returns of legumecereal rotation systems.

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“…tritici, which is the cause of the root disease ofwheat known as "take-all." These beneficial bacteria are associated with a spontaneous take-all decline that occurs after two or three successive outbreaks of the disease with continuous cropping to wheat (1). Take-all decline is the most studied of several documented cases of "induced suppression" to a plant pathogen that develops in soil with monoculture of the susceptible host (2).…”

mentioning

confidence: 99%

Molecular mechanisms of defense by rhizobacteria against root disease.

Cook

Thomashow

Weller

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

365

215

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Genetic resistance in plants to root diseases is rare, and agriculture depends instead on practices such as crop rotation and soil fumigation to control these diseases. "Induced suppression" is a natural phenomenon whereby a soil due to microbiological changes converts from conducive to suppressive to a soilborne pathogen during prolonged monoculture of the susceptible host. Our studies have focused on the wheat root disease "take-all," caused by the fungus Gaeumannomyces graminis var. tritici, and the role of bacteria in the wheat rhizosphere (rhizobacteria) in a well-documented induced suppression (take-all decline) that occurs in response to the disease and continued monoculture of wheat. The results summarized herein show that antibiotic production plays a significant role in both plant defense by and ecological competence of rhizobacteria. Production of phenazine and phloroglucinol antibiotics, as examples, account for most of the natural defense provided by fluorescent Pseudomonas strains isolated from among the diversity of rhizobacteria associated with take-all decline. There appear to be at least three levels of regulation of genes for antibiotic biosynthesis: environmental sensing, global regulation that ties antibiotic production to cellular metabolism, and regulatory loci linked to genes for pathway enzymes. Plant defense by rhizobacteria producing antibiotics on roots and as cohabitants with pathogens in infected tissues is analogous to defense by the plant's production of phytoalexins, even to the extent that an enzyme of the same chalcone/stilbene synthase family used to produce phytoalexins is used to produce 2,4-diacetylphloroglucinol. The defense strategy favored by selection pressure imposed on plants by soilborne pathogens may well be the ability of plants to support and respond to rhizosphere microorganisms antagonistic to these pathogens.

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Monoculture and Soilborne Plant Pathogens

Cited by 125 publications

References 21 publications

Wheat Cultivar-Specific Selection of 2,4-Diacetylphloroglucinol-Producing Fluorescent Pseudomonas Species from Resident Soil Populations

Wheat Cultivar-Specific Selection of 2,4-Diacetylphloroglucinol-Producing Fluorescent Pseudomonas Species from Resident Soil Populations

Profitability of diammonium phosphate use in bush and climbing bean-maize rotations in smallholder farms of Central Burundi

Molecular mechanisms of defense by rhizobacteria against root disease.

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