Control Of Apple Replant Disease Research Articles

Comparative Analysis of the Effects of Crude Metabolic Extracts of Three Biocontrol Bacteria on Microbial Community Structure Provides a New Strategy for the Biological Control of Apple Replant Disease

The crude metabolic extract from plant biocontrol bacteria plays a very important role in sustainable agricultural production. These extracts help maintain healthy plants and have very important application prospects in biotechnology related to alleviating apple replant disease (ARD). In this study, Bacillus velezensis XC1 (T1), Bacillus amyloliquefaciens QSB-6 (T2), and Lactobacillus reuteri LBR (T3) were examined to characterize the ability of their crude metabolic extracts to alleviate ARD. The high-throughput sequencing data of the soil microbial community structure were analyzed in relation to LBR crude metabolic extracts, and an extensive untargeted metabolomic analysis of UHPLC-Qex active components was performed. Active LC-MS/MS revealed that the main secondary metabolites involved in the biological control exerted by L. reuteri included 3-hydroxypropionaldehyde, extracellular polysaccharides (EPS), p-hydroxybenzoic acid, and azelaic acid. These crude metabolic extracts significantly inhibited the growth of soil pathogenic fungi, reduced the abundance of Fusarium, promoted the abundance of beneficial bacteria such as Pseudomonas, and optimized the soil microbial community structure. Improved modern extraction and purification technologies will be able to offer additional insights into the mechanism of action of these secondary metabolites and enable them to be used in biological preparations to prevent and control ARD in the future, as well as to allow harmful chemical fumigants to be discontinued.

Effects of Crystal Lime Sulfur Fumigation and Application of Root-Growth-Promoting Agents on the Control of Apple Replant Disease

Apple replant disease (ARD) is seriously hindering the development of the apple industry. This experiment assessed the effects of two different root-growth-promoting agents (Indoleacetic acid and nutrient elements) on the microbial environment of apple-replanted soil and the growth of apple rootstock Malus hupehensis Rehd. seedlings after fumigation with crystal lime sulfur. The results showed that the simultaneous application of crystal lime sulfur, indoleacetic acid, and nutrient elements (T4) improved the biomass of Malus hupehensis Rehd. seedlings. It also enhanced the activities of soil enzymes and root antioxidant enzymes (SOD, POD, CAT). Their activities were significantly higher than in the individual treatments and resulted in a decrease in malondialdehyde (MDA) content. The T4 treatment significantly increased the net photosynthetic rate and chlorophyll content of the plant, thus effectively increasing the plant growth status. After fumigation, the amount of soil microorganisms was reduced, and the amount of bacteria and actinomycetes was increased after mixed application with the root-growth-promoting agent. The abundance of different species such as Pseudallescheria, Guehomyces, Trichoderma, Bacillus, Gaiella, and Sphingomonas was effectively increased, and the amount of Fusarium oxysporum was reduced. Through correlation analysis between different species and plant and soil enzymes, we found that the different species were positively correlated with root respiration rate and SOD activity and negatively correlated with MDA content. The differentially accumulated microbial species may be the key microorganism that promotes plant growth. Therefore, the simultaneous application of crystal lime sulfur, indoleacetic acid, and nutrient elements can optimize the apple replant soil environment and promote the growth of Malus hupehensis Rehd. seedlings, and can be used to control apple replant disease.

Effects of Trichoderma harzianum Fertilizer on the Soil Environment of Malus hupehensis Rehd. Seedlings under Replant Conditions

A pot experiment was performed to investigate the effects of Trichoderma harzianum on the root morphology of Malus hupehensis Rehd. seedlings and their soil environment under replant conditions. The experiment consisted of four treatments: continuously cropped soil (CK1), methyl bromide fumigation (CK2), carrier substrate control (T1), and T. harzianum fertilizer (T2). Plant growth parameters, soil phenolic acid content, abundance of soil microorganisms, and root respiration rate were measured. Compared with CK1, plant height, basal diameter, and fresh weight were 34.58%, 27.55%, and 32.91% greater in T2; 11.35%, 12.10%, and 18.33% greater in T1; and 54.34%, 57.64%, and 45.74% greater in CK2. These metrics were significantly higher in the CK2 treatment than in the other treatments. The second highest values were recorded in the T2 treatment. Differences in root architecture were consistent with differences in biomass. Application of T. harzianum fertilizer was associated with increases of 45.45%, 120.06%, 86.44%, and 268.29% in the activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), respectively, and there was little difference between T2 and CK2. The contents of phlorizin and phloretin were 39.39% and 51.70% less in T2, respectively, and 17.85% and 18.14% less in T1, respectively, compared with CK1. Trichoderma harzianum fertilizer increased the abundance of bacteria and actinomycetes while decreasing that of fungi. The gene copy numbers of Fusarium oxysporum and Fusarium moniliforme were 64.30% and 49.35% less, respectively, in the T2 treatment. The fungus population and the gene copy number of Fusarium oxysporum and Fusarium moniliforme was the least in CK2 because of the good sterilization effect. The T. harzianum fertilizer showed satisfactory effects in promoting the root growth of M. hupehensis, increasing the root resistance, decreasing the soil phenolic acid content, and significantly reducing the gene copy number of F. oxysporum and F. moniliforme. In summary, T. harzianum fertilizer is an effective and green alternative for the prevention and control of apple replant disease (ARD).

Effect of Emerging Soil Chemical Amendments on the Replant Soil Environment and Growth of Malus hupehensis Rehd. Seedlings.

The effects of different soil chemical amendments (T1, 1‰ quicklime + 1‰ superphosphate; T2, 1‰ quicklime; T3, 1‰ superphosphate) on the soil environment and growth of Malus hupehensis Rehd. seedlings in aged apple orchard soil were studied to provide new insight into the prevention and control of apple replant disease. The amendments differed in their ability to ameliorate the soil environment; nevertheless, they all promoted the growth of M. hupehensis Rehd. seedlings, and the greatest enhancement of growth was observed in T1. On August 15, 2018, soil urease, sucrase, phosphatase, and catalase activities were 1.67 times, 1.32 times, 1.62 times, and 1.35 times higher in T1 compared with CK, respectively. The soil pH increased, which alleviated soil acidification. T1 also promoted the renewal of the community structure and the diversity of soil microorganisms. The copy numbers of Fusarium solani and Fusarium oxysporum were 71.96 and 70.30% lower in T1 compared with CK, respectively. The seedling height and root length of M. hupehensis Rehd. seedlings increased by 40.97 and 289.69% in T1 compared with CK, respectively. Therefore, soil replanting obstacles can be overcome with the application of quicklime and superphosphate; these soil chemical amendments also improve the soil microbial ecological environment and promote the growth of M. hupehensis Rehd. seedlings.

Field scale application of Brassica seed meal and anaerobic soil disinfestation for the control of apple replant disease

Apple replant disease caused by a complex of soil-borne fungi, oomycetes, and nematodes causes stunting and reduced yields when apples are planted in locations previously cropped to tree fruit. Anaerobic soil disinfestation and bio-renovation using mustard seed meals have successfully mitigated replant disease in greenhouse trials and small field plots. The objective of this study was to examine the efficacy of Brassica seed meal and anaerobic soil disinfestation for the control of replant disease at a commercial scale in apples. At three 0.4 to 5 ha field sites in Washington, United States anaerobic soil disinfestation and Brassica seed meal bio-renovation were compared to non-treated and fumigation with 1,3-dichloropropene/chloropicrin controls. Brassica seed meal treatments significantly altered composition of the bulk soil and rhizosphere microbiomes and resulted in apple tree growth as great or greater than fumigated controls across all three study locations. Anaerobic soil disinfestation resulted in significant changes to composition of the rhizosphere microbiome and tree growth that was greater than the no-treatment control in three of four experiments. Our findings indicate that both methods may serve as biologically effective alternatives to soil fumigation for control of apple replant disease, though further modifications may be required to ensure their economic feasibility.

Comprehensive analysis of the apple rhizobiome as influenced by different Brassica seed meals and rootstocks in the same soil/plant system

Replant disease refers to the poor growth of trees when attempting to establish the same or related species on old orchard sites. The use of pre-plant Brassicaceae seed meal (SM) soil amendments in combination with apple replant disease-tolerant rootstock genotypes has been shown to be a promising strategy for the control of apple replant disease (ARD). However, optimizing microorganism-driven protection of apple roots from infection by multiple soil-borne pathogens requires a more comprehensive understanding of how “effective” vs. “ineffective” Brassicaceae seed meal × rootstock genotype disease control systems modulate the composition of rhizosphere microbial communities. In particular, the community of oomycetes associated with the apple rhizosphere remains relatively unexplored compared with bacteria and fungi. To address these issues, we sequenced the root associated bacterial, fungal, and oomycete communities of apple replant disease tolerant (G.210) and susceptible (M.26) rootstocks when grown in an orchard replant soil amended with different Brassicaceae seed meal formulations (Brassica juncea + Sinapis alba, B. juncea, and Brassica napus) previously shown to provide varying levels of replant disease control. Multiple microbial components were associated with observed growth differences between “effective” and “ineffective” disease control systems including the absolute abundance of Ilyonectria/Cylindrocarpon in fine root tissue. Amplicon sequencing provided a more detailed picture of the genetic diversity of oomycete groups in the apple rhizosphere than previously appreciated, and highlighted the variability in oomycete community structure between different rootstock × seed meal disease control systems. In Brassica juncea + Sinapis alba SM-structured rhizospheres, the ARD-tolerant rootstock (G.210) harbored higher relative abundances of Peronosporales with reduced potential to infect apple roots and incite replant disease (such as Peronospora destructor and P. acanthicum), whereas the Peronosporales community associated with the sensitive rootstock (M.26) was dominated by the ARD-specific pathogen Phytophthora cactorum. In addition, Brassica juncea + Sinapis alba SM-structured microbiomes were characterized by numerous bacterial and fungal taxa with the potential for biocontrol, biodegradation and bioremediation. Taken together, these results support the hypothesis that particular Brassicaceae SM soil amendments not only provide “effective” disease control, but also promote microbiomes which are likely to contribute to long-term orchard soil health in many other ways. Overall, this comprehensive analysis highlights the significance of the rootstock × seed meal interaction on bacterial, fungal, and oomycete communities within the apple rhizosphere of “effective” vs. “ineffective” disease control systems and the potential influence of these elements on the dynamics of apple replant disease.

Field Evaluation of Reduced Rate Brassicaceae Seed Meal Amendment and Rootstock Genotype on the Microbiome and Control of Apple Replant Disease.

An orchard field trial was conducted to assess the utility of reduced rate Brassicaceae seed meal (SM) amendment in concert with specific rootstock genotypes for effective control of apple replant disease. Three amendment rates of a 1:1 formulation of Brassica juncea-Sinapis alba SM were compared with preplant 1,3-dichloropropene/chloropicrin soil fumigation for disease control efficacy. When applied at the highest rate (6.6 t ha-1) in the spring of planting, SM caused significant phytotoxicity and tree mortality, which was higher for Gala/M.26 than for Gala/G.41 but was not observed at SM application rates of 2.2 or 4.4 t ha-1. SM treatment resulted in growth and yield increases of Gala/M.26 and Gala/G.41 trees in a manner similar to the fumigation treatment and significantly greater than the no treatment control. Tree growth in soils treated with SM at 4.4 t ha-1 was similar or superior to that obtained with SM at 6.6 t ha-1 and superior to that attained at an SM application rate of 2.2 t ha-1. Soil fumigation and all SM treatments reduced Pratylenchus penetrans root infestation relative to the control treatment at the end of the initial growing season. Lesion nematode root densities in the fumigation treatment, but not SM treatments, rapidly recovered and were indistinguishable from the control at the end of the second growing season. Soil fumigation and all SM treatments significantly suppressed Pythium spp. root infection relative to the control. Trees grafted to rootstock G.41 possessed lower P. penetrans root densities relative to trees grafted to rootstock M.26. One year after planting, composition of microbial communities from SM-amended soils was distinct from those detected in control and fumigated soils, and the differences were amplified with increasing SM application rate. Specific fungal and bacterial phyla associated with suppression of plant pathogens were more abundant in SM-treated soil relative to the control, and they were similar in abundance in 4.4- and 6.6-t ha-1 SM treatments. Findings from this study demonstrated that use of the appropriate apple rootstock genotype will allow for effective replant disease control at SM application rates significantly less than that utilized previously (6.6 t ha-1).

Interaction of Brassicaceae Seed Meal Soil Amendment and Apple Rootstock Genotype on Microbiome Structure and Replant Disease Suppression.

Preplant soil application of a Brassica juncea-Sinapis alba seed meal formulation (SM) at a rate of 6.6 t ha-1 alters composition of the orchard soil microbiome in a manner that yields sustainable long-term suppression of soilborne pathogens in apple production systems. However, the cost of SM amendment has hindered the adoption of this tactic to manage apple replant disease in commercial orchards. Greenhouse trials were conducted to assess the effect of reduced SM application rates in concert with apple rootstock genotype on structure of the rhizosphere microbiome and associated disease control outcomes. At all application rates assessed, SM treatment increased tree growth and reduced disease development relative to the control. In general, total tree biomass and leader shoot length were similar in soils treated with SM at 4.4 or 6.6 t ha-1 regardless of rootstock genotype. Equivalent increase in tree biomass when cultivated in soil treated at the lowest and highest SM amendment rate was attained when used in conjunction with G.41 or G.210 apple rootstocks. Suppression of Pythium spp. or Pratylenchus penetrans root densities was similar at all SM application rates. When cultivated in nontreated replant orchard soil, Geneva rootstocks (G.41 and G.210) exhibited lower levels of Pythium spp. and P. penetrans root colonization relative to Malling rootstocks (M.9 and MM.106). For a given rootstock, structure of the rhizosphere microbiome was similar in soils treated with SM at 4.4 and 6.6 t ha-1. G.41 and G.210 rootstocks but not M.9 or MM.106 cultivated in soil treated with SM at 2.2 t ha-1 possessed a rhizosphere bacterial community structure that differed significantly from the control. Findings indicate that effective control of apple replant disease may be attained at lower SM amendment rates than employed previously, with lower effective rates possible when integrated with tolerant rootstock genotypes such as G.41 or G.210.

Carbon source-dependent antifungal and nematicidal volatiles derived during anaerobic soil disinfestation

Anaerobic soil disinfestation (ASD) has been shown to be effective in the control of a wide range of soil–borne plant pathogens but has not been examined as a means for disease control in perennial fruit crops such as apple. Since ASD has demonstrated a broad spectrum of biological activity, it may be well suited as an alternative to current fumigation–based control of apple replant disease (ARD) which is caused by a diverse pathogen complex. The efficacy of ASD for control of ARD pathogens was evaluated in growth chamber experiments using soils from two orchard sites having a history of the disease. Suppression of Pratylenchus penetrans apple root densities was dependent upon carbon source utilized during the ASD process. Volatiles emitted during the anaerobic phase from soils treated with ethanol, grass residues, or Brassica juncea seed meal as the carbon input effectively retarded growth of Rhizoctonia solani AG–5, Pythium ultimum and Fusarium oxysporum. Each carbon amendment generated a unique volatile profile produced in the treated orchard soil during ASD. Allyl isothiocyanate (AITC) and dimethyl trisulphide (DMTS) were emitted from B. juncea SM treated soils whereas the latter and 2–ethyl–1–hexanol were detected in soils treated with grass residues. When assayed individually using pure standards, Decanal, DMTS, and AITC retarded in vitro growth of all three fungal/oomycete pathogens. Nonanal was inhibitory toward only P. ultimum and R. solani AG–5, whereas 2–ethyl–1–hexanol only suppressed growth of P. ultimum. AITC and DMTS caused significantly higher mortality of P. penetrans compared to other tested volatiles. These findings demonstrate that carbon source–dependent volatile chemistries contribute significantly but not exclusively to suppression of certain ARD pathogens during the ASD process.

Efficacy of Brassicaceous Seed Meal Formulations for the Control of Apple Replant Disease in Conventional and Organic Production Systems.

The efficacy of brassicaceous seed meals for the control of apple replant disease and the effects of such treatments on the causal pathogen complex were examined in conventional and organic production systems. When used in conjunction with a postplant application of mefenoxam, Brassica juncea and Sinapis alba seed meal soil amendments were as effective as preplant fumigation of soil with 1,3-dichloropropene-chloropicrin in terms of disease control, tree growth, and overall fruit yields of Gala/M26. Brassica napus seed meal amendment-mefenoxam soil drench also enhanced yields in a manner comparable to preplant fumigation, but vegetative growth was intermediate between the control and fumigation treatments. When applied alone, seed meal amendments failed to enhance tree growth or control disease to the level attained in response to soil fumigation. Postplant mefenoxam treatments revealed that failure of seed meal amendments to enhance tree growth and yield when used independently was due, at least in part, to increased apple root infection by Pythium spp. in B. napus and S. alba seed meal-amended soils, and by Phytophthora cambivora in B. juncea-amended soil. As mefenoxam treatment is not compatible with organic cropping systems, a seed meal blend was formulated which, based upon biological activity, was predicted to suppress known components of the target pathogen complex without need of additional treatment. Gala/M26 trees planted in soils treated with a 1:1 ratio of B. juncea:B. napus seed meal blend performed as well in terms of disease control and vegetative growth as trees cultivated in fumigated soil at an organic-certified orchard. Because these trials utilized the highly susceptible rootstock M26, the results demonstrate that these amendments are a viable alternative to soil fumigation for the control of apple replant disease in both conventional and organic systems.

Maritime Regional Meeting, 2005

Evaluation of at-planting in-furrow application of Phostrol™ and Ridomil Gold ® 480EC for control of pink rot in potato. K.I.AI-Mughrabi and R.D. Peters. Potato Development Centre, New Brunswick and Department of Agriculture, Fisheries and Aquaculture, 39 Barker Lance, Wicklow, NB E7L 3S4, Canada; and (R.D.P.) Crops and Livestock Research, Agriculture and Agri-food Canada, 440 University Avenue, Charlottetown, PE C1A 4N6, Canada. Biological control of apple replant disease P.G. Braun and K.K. Fuller. Atlantic Food and Horticulture Research Centre, Agriculture and Agri-Food Canada, 32 Main Street Kentville, NS B4N 1J5, Canada. Potato gene expression during infection of tubers by Streptomyces scabiei. C. Goyer and J. Zeng. Potato Research Centre, Agriculture and Agri-Food Canada, P.O. Box 20280, 850 Licoln Road, Fredericton, NB E3B 4Z7, Canada. Suppression of potato early blight (in vivo) and germination of Alternaria spp. conidia (in vitro) with strobilurin fungicides. W. MacDonald, R.D. Peters, R.H. Coffin, and C. Lacroix. Department of Biology, University of Prince Edward Island, 550 University Avenue, Charlotttetown, PE C1A 4P3, Canada; (R.D.P.) Crops and Livestock Research Centre, Agriculture and Agri-Food Canada, 440 University Avenue, Charlottetown, PE C1A 4N6, Canada; and (R.H.C.) Cavendish Farms, New Annan, Kensington, PE C0B 1M0, Canada. Plant pathology and potato breeding: interlaced disciplines. A. Murphy. Potato Research Centre, Agriculture and Agru-Food Canada, P.O. Box 20280, 850 Lincoln Road, Frederecton, NB E3B 4Z7, Canada. Systemic acquired resistance against potato virus Y in tobacco is salicylate mediated and ethylene independent. X. Nie. Potato Research Centre, Agriculture amd Agri-Food Canada, 850 Lincoln Road, P.O. Box 20280, Fredericton, NB E3B 4Z7, Canada. Increasing the sustainability of potato production, in Atlantic Canada, with crop rotation and conservation tillage. R.D. Peters, M.R. Carter, J.B. Sanderson, and A.V. Sturz. Crops and Livestock Research Centre, Agriculture and Agri-Food Canada, 440 University Avenue, Charlottetown, PE C1A 4N6, Canada; and (A.V.S.) Prince Edward Island Department of Agriculture and Forestry, Plant Health Research and Diagnostics, P.O. Box 1600, Charlottetown, PE C1A 7N3, Canada. Host-pthogen interactions of various combinations of verticillium spp. inoculum in potato. N. Robinson, H.W. (Bud) Platt, L. Hale, and V. MacLean. Crops and Livestock Research Center, Agriculture and Agri-Food Canada; and (L.H.) Department of Biology, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE C1A 4P3, Canada. Real-time PCR assay for the detection of potato viruses in a triplex format. M. Singh, R.P. Singh, and R. Coffin. Agricultural Certification Services, 1030 Lincoln Road, Frederiction, NB E3B 8B7, Canada; (R.P.S.) Potato Research Centre, Agriculture and Agri-Food Canada; and (R.C.) Cavendish Farms, P.O. 3500, Summerside, PE C1N 5J5, Canada. Viroids from oranamental plants – a potential threat to tomato and potato crops. R.P. Singh. Potato Research Centre, Agriculture and Agri-Food Canada, 850 Lincold Road, Fredericton, NB E3B 4T7 canada, Reassessment of the presence of species of the genus Pospiviroid in floral parts, using reverse transcription - PCR and infectivity assays R.P. Singh. Potato Research Centre, Agriculture and Agri-Food Canada, 850 Lincoln Road, Fredericton, NB E3B 4Z7, Canada. Viroid RNAs, PCR fragments, and plasmid purification simplified by spotting an alkaline extract onto nitrocellulose membrance. R.P. Singh, A.D. Dilworth, M. Singh, and K.M. Babock. Potato Research Centre, Agriculture and Agri-Food Canada, 850 Lincoln Road, Fredericton, NB E3B 4Z7, Canada; and (M.S., K.M.B.) Agricultural Certification Services, 1030 Lincoln Road, Fredericton, NB E3B 8B7, Canada. Sensitivity to mefenoxam of Canadian strains of Phytophthora erythroseptica the causal agent of potato pink rot, and their interactions with Phytophthora infestans in tubers. P.D. Young, R.D. Peters, H.W. (Bud) Platt, and L.R. Hale. Department of Biologu, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE C1A 4P3, Canada; and (R.D.P., H.W.P.) Crops and Livestock Research Centre, Agriculture and Agri-Food Canada, 440 University Avenue, Charlottetown, PE C1A 4N6, Canada.

Comparative Field Efficacy of Management Strategies Containing Brassica napus Seed Meal or Green Manure for the Control of Apple Replant Disease.

Alternative management strategies to the use of preplant soil fumigation for the control of apple replant disease (ARD), including cover crops and strategies incorporating Brassica napus seed meal (rape seed meal [RSM]) amendment as the central component, were evaluated in the orchard. A 1-year wheat cover crop consisting of three short-term cropping periods with plant material removed at the end of each growth period and a 3-year B. napus green manure significantly enhanced vegetative growth and yield of Gala/M26. However, in each instance, the resulting disease control and growth response were inferior to that achieved through preplant methyl bromide soil fumigation. A 3-year bare fallow and 1- or 2-year B. napus green manure neither suppressed disease development nor enhanced tree growth. Preplant RSM amendment in conjunction with a postplant mefenoxam soil drench provided effective suppression of ARD, and the resulting tree growth and yield were comparable with that attained in response to 1,3- dichloropropene-chloropicrin fumigation in one orchard. At a second orchard, the growth response attained with the alternative treatment was inferior to preplant soil fumigation, which was associated with an apparent re-infestation of RSM-treated soils and tree roots by Pratylenchus spp. Application of RSM after wheat cropping or in conjunction with soil solarization provided an intermediate level of disease control and a corresponding reduction in growth and yield of apple relative to preplant fumigation at both sites.

Modification of fluorescent pseudomonad community and control of apple replant disease induced in a wheat cultivar-specific manner

Apple orchard soils were cropped for three successive 28-day growth cycles with a perennial ryegrass/annual ryegrass mixture or 1 of 11 wheat cultivars prior to planting with Gala apple seedlings. Prior cropping of soils with ryegrass had no significant impact on growth of apple, but cultivation with some, but not all, wheat cultivars substantially enhanced apple seedling growth. Enhanced growth of apple was associated with a reduction in root infection by the dominant fungal pathogens resident to the respective orchard soils. Wheat cultivars that enhanced growth of apple modified the genetic and species composition of the fluorescent pseudomonad population resident to orchard soil. The fluorescent pseudomonad population from soils cropped with wheat cultivars that enhanced apple seedling growth possessed a higher capacity to inhibit in vitro growth of multiple elements of the fungal complex that incites apple replant disease than did the population from non-treated orchard soil or soil cropped with a wheat cultivar that did not enhance growth of apple. Application of wheat root exudates to soil also modified the antagonistic potential and composition of the fluorescent pseudomonad population in a cultivar-specific manner. This study demonstrates the significant role of plant genotype in determining composition of the saprophytic soil microbial community. It also establishes the need to consider not only plant species but also plant genotype when evaluating the potential benefit of specific cover crops as a component within a systems approach for the management of soilborne plant diseases.

RESULTS OF POT EXPERIMENTS ON CONTROL OF APPLE REPLANT DISEASE

RESULTS OF POT EXPERIMENTS ON CONTROL OF APPLE REPLANT DISEASE

DEVELOPMENT OF BIOLOGICAL CONTROL OF APPLE REPLANT DISEASE

DEVELOPMENT OF BIOLOGICAL CONTROL OF APPLE REPLANT DISEASE

BIOLOGICAL CONTROL OF APPLE REPLANT DISEASE

BIOLOGICAL CONTROL OF APPLE REPLANT DISEASE

The Effect of Glomus mosseae and Enterobacter aerogenes on Apple Seedlings Grown in Apple Replant Disease Soil

AbstractInoculation of apple seedlings with the mycorrhizal fungus Glomus mosseae significantly increased their growth in apple replant disease soil that was neither pasteurized nor fertilized with monoammonium phosphate. The application of Enterobacter aerogenes and peat suppressed the stunting effect observed in apple replant disease soil. These results suggest the potential of using G. mosseae alone or a E.aerogenes and peat combination for the control of apple replant disease.

Chemical and biological treatments for control of apple replant disease in British Columbia

Chemical and biological treatments for control of apple replant disease in British Columbia

Control of Apple Replant Disease with Formaldehyde in Washington

Control of Apple Replant Disease with Formaldehyde in Washington

Control of Apple Replant Disease with Formaldehyde in Washington

Control of Apple Replant Disease with Formaldehyde in Washington