Wheat yield depression associated with conservation tillage caused by root pathogens in the soil not phytotoxins from the straw

Cook, Robert; Haglund, W. A.

doi:10.1016/0038-0717(91)90024-e

Cited by 93 publications

(45 citation statements)

References 23 publications

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“…was tested for production of extracellular proteases and HCN and for the presence of two genes for antibiotic production. Between cycles, root residues were left in soil to mimic conservation tillage practices (Gebhardt et al 1985) which may increase pathogen loads (Cook and Haglund 1991). To determine effects of previous crop, soil previously cycled with wheat seedlings were planted with sorghum and soils planted with each sorghum genotype were planted with wheat.…”

Section: Discussionmentioning

confidence: 99%

Effect of sorghum seedlings, and previous crop, on soil fluorescent Pseudomonas spp.

2008

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Hypotheses in which sorghum seedlings [Sorghum bicolor (L.) Moench] of different genotypes will differentially modify soil microorganisms and will affect subsequent planting of wheat (Triticum aestivum L.) seedlings, were tested. Wheat cultivar Lewjain, and sorghum genotypes Redlan and RTx433, were planted into soils previously planted with wheat or sorghum in growth chamber experiments. Total culturable fungi and oomycetes, and fluorescent Pseudomonas spp. numbers (cfu) were determined. Pseudomonads were screened for hydrogen cyanide (HCN) production, for the presence of the phlD gene for 2,4-diacetylphloroglucinol production (Phl) and for a region of the operon involved in phenazine-1-carboxylic acid (PCA) production. Pasteurized soils were inoculated with rifampicin-marked strains of Pseudomonas fluorescens then planted with Lewjain, Redlan and RTx433 to assess rhizosphere and soil colonization. Effects of plant species, sorghum genotype and previous crop on culturable fungi and oomycetes, and pseudomonad numbers (cfu g −1 soil) were statistically significant. Soils planted with RTx433 or Lewjain had greater numbers of fungal cfu than soils planted with Redlan. When Lewjain seedlings were grown in soil previously planted with RTx433, there were greater numbers of fungal cfu than when Lewjain was planted into Redlan soil. Wheat planted into wheat soil resulted in statistically significantly fewer numbers of pseudomonads than when planted into sorghum soil. Overall, percentages of HCN-producing pseudomonads increased, especially when wheat seedlings were planted in wheat soil. For most treatments, percent of isolates with Phl declined, except when Redlan was planted into Redlan soil, which resulted in increased Phl isolates. When rifampicin-marked P. fluorescens isolates were applied to pasteurized soil, sorghum seedlings sustained rhizosphere and soil populations similar to those on wheat. Sorghum genotypes may differ in associations with soil microorganisms, Plant Soil

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Section: Discussionmentioning

confidence: 99%

Effect of sorghum seedlings, and previous crop, on soil fluorescent Pseudomonas spp.

2008

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“…Cold soil at the depth of seeding is itself stressful to young plants during seedling emergence, but in the case of wheat, the low-temperature stress predisposes the plants to greater pressure from root disease (6, 7). Fresh (unweathered) wheat straw also can serve as a source of readily available carbon and energy for Pythium species, but the straw itself is not toxic to young wheat plants, as was once thought (8). Pythium species are ubiquitous in agricultural soils, making it necessary to design experiments that separate the direct effects of crop residues and associated cold soil on the young plants from the predisposing and other effects of these variables on Pythium root rot.…”

Section: Yield-limiting Hazards Of Direct Seedingmentioning

confidence: 99%

“…This can also mean expense, but no income, from that field, depending on the duration of the break (5). Soil fumigation with methyl bromide has been used in Washington state as an experimental tool to reveal the high yields possible with continuous (monoculture) direct-seeded wheat and barley sequences (7,8). However, fumigation is economical only for certain high-value horticultural crops, such as strawberries in California and tomatoes in Florida.…”

Section: Yield-limiting Hazards Of Direct Seedingmentioning

confidence: 99%

Toward cropping systems that enhance productivity and sustainability

2006

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

139

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The defining features of any cropping system are (i) the crop rotation and (ii) the kind or intensity of tillage. The trend worldwide starting in the late 20th century has been (i) to specialize competitively in the production of two, three, a single, or closely related crops such as different market classes of wheat and barley, and (ii) to use direct seeding, also known as no-till, to cut costs and save soil, time, and fuel. The availability of glyphosate-and insect-resistant varieties of soybeans, corn, cotton, and canola has helped greatly to address weed and insect pest pressures favored by direct seeding these crops. However, little has been done through genetics and breeding to address diseases caused by residue-and soil-inhabiting pathogens that remain major obstacles to wider adoption of these potentially more productive and sustainable systems. Instead, the gains have been due largely to innovations in management, including enhancement of root defense by antibiotic-producing rhizosphere-inhabiting bacteria inhibitory to root pathogens. Historically, new varieties have facilitated wider adoption of new management, and changes in management have facilitated wider adoption of new varieties. Although actual yields may be lower in direct-seed compared with conventional cropping systems, largely due to diseases, the yield potential is higher because of more available water and increases in soil organic matter. Achieving the full production potential of these more-sustainable cropping systems must now await the development of varieties adapted to or resistant to the hazards shown to account for the yield depressions associated with direct seeding.

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“…That Rhizoctonia root rot contributed to the stunting and spindly growth of seedlings in these sods was further suggested by the abundance of roots with diagnostic spear-tips. It has been shown repeatedly that the increased growth of wheat in response to soil fumigation is the result of control of root diseases, including Pythium and Rhizoctonia root rots, and not the increase in the availability of nitrogen associated with soil fumigation (Cook & Haglund, 1982;Cook et al, 1987;Cook & Haglund, 1991). Likewise, if the growth response obtained through tillage were simply the result of changes in soil physical properties, a similar enhanced growth response would not have been achieved through soil fumigation.…”

Section: Discussionmentioning

confidence: 99%

“…Likewise, in this same region, wheat direct-drilled into bluegrass sod grows and yields significantly better if the bluegrass residue is burned prior to planting (Cook, unpublished observations). Cook & Haglund (1991) demonstrated that the improvement in yield of direct-drilled wheat in response to burning stubble from the previous wheat crop was due to a reduction in damage from root diseases, namely take-all caused by Gaeumannomyces graminis var. tritici Rhizoctonia root rot caused mainly by Rhizoctonia solani AG-8, and Pythium root rot caused by several species of Pythium.…”

Section: Introductionmentioning

confidence: 99%

Influence of field burning and soil treatments on growth of wheat after Kentucky bluegrass, and effect of Rhizoctonia cerealis on bluegrass emergence and growth

1997

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Studies were conducted to assess the importance of soil-borne pathogens as impediments to the production of direct-drilled wheat following Kentucky bluegrass in rotation. Bluegrass sods were collected as cores from commercial seed fields in October (after open-field burning) and in December and March (after exposure to normal freezing and thawing), treated with glyphosate after a 2-to 3-week period of green-up in the glasshouse, and then planted to wheat 21 days later. Wheat seedlings in the 3-to 4-leaf stage were stunted and spindly in either burned or nonburned sods collected in October, but grew significantly better in burned than nonburned sods collected in December and March. Fumigation (methyl bromide), simulated tillage, and application of metalaxyl as a drench, singly or as combined treatments, improved the growth of wheat in nonburned sods. Growth of wheat in nontreated burned sods collected after frost had penetrated the upper portions was equivalent to that in fumigated sods. Experimental freezing at ¹20ЊC for up to 96 h, of burned and nonburned sods collected in October, followed by thawing also improved the growth of wheat subsequently sown directly into these sods. The stunted and spindly seedlings had roots girdled and severed by lesions typical of Rhizoctonia root rot. Isolates of Rhizoctonia cerealis were recovered from these roots and caused poor seedling emergence and stunted root and shoot growth of both wheat and bluegrass. The results suggest that both R. cerealis and Pythium spp. are potentially important soil-borne pathogens of wheat when following Kentucky bluegrass in rotation and that burning done routinely to improve the yield of bluegrass seed can also reduce the potential for damage caused by Rhizoctonia and Pythium root rots of wheat seeded directly into bluegrass sod.

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Wheat yield depression associated with conservation tillage caused by root pathogens in the soil not phytotoxins from the straw

Cited by 93 publications

References 23 publications

Effect of sorghum seedlings, and previous crop, on soil fluorescent Pseudomonas spp.

Effect of sorghum seedlings, and previous crop, on soil fluorescent Pseudomonas spp.

Toward cropping systems that enhance productivity and sustainability

Influence of field burning and soil treatments on growth of wheat after Kentucky bluegrass, and effect of Rhizoctonia cerealis on bluegrass emergence and growth

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