PROJECT: S-269: Biological Control and Management of Soilborne Plant Pathogens for Sustainable Crop Production
DATE Project was:
Activated under RRF:10/01/95
Revised:
Terminated: 09/30/2000
COOPERATING AGENCIES AND PRINCIPAL LEADERS:
| SAES: | Alabama | J. Kloepper |
| Arkansas | C. S. Rothrock | |
| Florida | M. L. Elliott*, L. E. Datnoff | |
| Georgia | D. R. Sumner | |
| Indiana | D. M. Huber | |
| Kentucky | J. W. Hendrix | |
| Louisiana | R. W. Schneider*, J. W. Hoy | |
| Mississippi | W. E. Batson | |
| North Carolina | D. M. Benson | |
| Oklahoma | L. L. Singleton*, K. E. Conway | |
| South Carolina | A. P. Keinath | |
| Tennessee | B. H. Ownley | |
| Texas | P. M. Thaxton, K. M. El-Zik* | |
| USDA ARS: | Texas | C. R. Howell |
| Adminstrative | Advisor: | Everett Emino |
| CSREES: | Robin Huettel |
REASONS FOR TERMINATION: Partial completion of objectives. Funds terminated.
EXPENDITURES:
Expenditures of Regional Research Funds:
Hatch Funds:
Other Funds:
(Leave blank, data will be entered by the Regional Research Office, CSREES)
MAJOR ACCOMPLISHMENTS: Summarize in a concise form the findings for each objective for the entire duration of the project.
Objective 1. Selection and optimization of biological control agents and evaluation of seed treatment and other application techniques, to enhance the biological control of diseases caused by soilborne plant pathogens.
Regional biological seed treatment trials were conducted each year for a 5-yr period using Trichoderma spp., a Trichoderma sp. mixed with Paenibacillus macerans, Bacillus spp., Pseudomonas spp., Laetisaria arvalis, binculeate Rhizoctonia sp. and Burkholderia cepacia compared with nontreated seeds, fungicide seed treatments, and formulating agents (carriers) on cotton (12 states, 13 locations), snapbean (11 states) and wheat (6 states). At cotton test sites two T. virens isolates provided final plant stands equal to the fungicide seed treatments. Pathogens controlled were Pythium or Rhizoctonia. Five treatments (all T. virens) resulted in final cotton stands that were significantly greater than the nontreated control. Three treatments resulted in final cotton stands that were significantly reduced from the nontreated control indicating a possible phytotoxic effect. The best treatment overall appeared to be the Trichoderma and Paenibacillus mixture.
Cotton seed treated with Bacillus or Paenibacillus spp. had populations ranging from 1.85 to 4.45 log10 CFU per seed at delivery and 2.0 to 4.51 log10 CFU per seed at planting. While the Dagger G treatment had a high population of Pseudomonas at delivery, they were not maintained for all planting sites; two sites (AL and TX-Gust) had undetectable levels at planting. Trichoderma populations on the cotton seed ranged from 1.93 to 2.65 log10 CFU per seed at delivery and from 1.73 to 2.56 log10 CFU per seed at planting. The addition of the chemical fungicide Apron (metalaxyl) had mixed effects on the isolates. There was no effect on isolate TV-117 of T. virens. Isolate TV-116 populations of T. virens were reduced by Apron, but G-6 populations of T. virens were increased by the fungicide.
Seed treatment of cotton with, and subsequent growth on seedling roots by, Trichoderma virens induces the synthesis in the roots of the antifungal compounds desoxyhemi-gossypol, hemigossypol and gossypol. These compounds, which are toxic to the pathogen, render the cotton root resistant to subsequent infection by R. solani. The phytoalexin stimulatory compound produced by T. virens has been isolated and shown to be a protein of approximately 18 KB size. Seed treatment of cotton with T. virens strains, followed by stem inoculation of developing plants in the six true leaf stage with Verticillium dahliae, resulted in a significant reduction in foliar symptoms of Verticillium wilt when compared to the inoculated controls with no seed treatment. This indicates that seed treatment may induce a systemic resistance response in plants. Cotton seed treatment with wheat bran stimulated germination of P. aphanidermatum oospores, while the germination of naked cotton seed in infested soil did not.
Bacillus subtilis (GB03) applied to 72-hr-old cotton radicles significantly reduced symptom ratings from Fusarium oxysporum. However, age of cotton radicles at introduction of B. subtilis or P. fluorescens (Dagger G) had no significant effect on the ability of either bacterium to reduce mean symptoms or the rate of symptom development induced by P. ultimum. At least 5 days between treatment of cotton seed with B. subtilis or P. fluorescens and challenge with T. basicola were needed before tissue was protected.
In the snap bean trials, over the same 5-yr period at all sites, only T. harzianum and Paenibacillus pabuli improved stands over the nontreated control. Laetisaria arvalis slightly reduced stands. Pathogens controlled were R. solani and Pythium spp. Yields in the snap bean trials were confounded by various problems other than disease, and other methods for predicting yield will be considered in future tests. In wheat seed trials, B. cepacia, P. fluorescens, and one isolate of Bacillus subtilis produced stands better than the nontreated control, but none were as effective as metalaxyl. In addition, the initial seed populations of the biocontrol agents at the time of planting were determined through dilution assays. Snap bean seed treated with Bacillus spp. had populations ranging from 3.11 to 6.03 log10 CFU per seed at delivery to cooperators. The range of populations at planting was 3.29 to 6.45 log 10 CFU per seed. Four of the Bacillus treatments and the one fungal treatment, Beauveria bassiana, had no significant differences in populations from delivery to the last planting date. Comparisons were made for Bacillus GB03 in regards to effect of chemical pesticides on seed populations. The populations significantly increased with the addition of these pesticides, as compared to populations on seed that had no pesticides added to them
Trichoderma harzianum and P. macerans alone or in combination were able to effectively colonize tomato 'BHN 422' roots. The number of colony forming units per gram of fresh root tissue was about 5 x 105 for T. harzianum alone, 1 x 106 P. macerans alone and in combination, 1.4 x 104 propagules of T. harzianum and 6.6 x 106 propagules of P. macerans. Trichoderma harzianum and P. macerans alone or in combination significantly affected the growth of tomato transplants in the greenhouse and after outplanting into the field 30 days later. In the greenhouse, petiole numbers were increased between 6 to 9%, heights 8 to 18.8%, stem caliper 10 to 13.6%, leaf area 7 to 21%, petiole fresh weight 25 to 38% and root fresh weight 50%. In the field, petiole numbers were increased between 3 to 5%, heights 2 to 8% and stem caliper 1 to 7%. Trichoderma harzianum and Paenibacillus macerans significantly reduced severity of Fusarium crown and root rot. Trichoderma harzianum reduced the severity of Fusarium crown and root rot by 12% and P. macerans 9% in comparison to the untreated control in the nonfumigated treatments. No differences were observed between the biologicals and the untreated control in the methyl bromide treated plots.
Induced resistance was demonstrated as a mechanism of biocontrol in
a poinsettia-Rhizoctonia pathosystem when binucleate Rhizoctonia
spp. (BNR) were introduced to stock plants. Subsequently, cuttings taken
from BNR treated stock plants were protected from stem rot caused by R.
solani. Since the pathogen and biocontrol agent were separated in time
and space, induced resistance in the plant accounted for the protection.
BNR fungi in Pesta or rice flour formulations stored at 0.13 and 0.33 water
activity had longer shelf life than formulations at 0.53 or 0.75 water
activity. Storage at 4 C promoted shelf life of formulations in addition
to low water activity. Rifampcin-resistant isolates of strain 5.5B of Burkholderia
cepacia varied in production of pyrrolnitrin, an antibiotic active
against R. solani. Isolates that lost ability to produce
pyrrolnitrin did not control Rhizoctonia stem rot in poinsettia.
Objective 2. Determination of the applicability and efficacy of biological control agents across different pathogens, crop species and cultivars to select biological control agents for more effective disease control.
Seed treatments with T. virens strains in combination with fungicide treatments were evaluated for control of cotton seedling disease caused by R. solani. Better biocontrol was obtained with combination seed treatments of metalaxyl + T. virens + a bacterial agent than with any agent alone. The laser aminopeptidase profile system for microbial identification has been further adapted for rapid characterization of biological control organisms. Collard and kale cultivars were evaluated for resistance to Fusarium oxysporum f. sp. conglutinans in a naturally infested field. All five kale cultivars were highly susceptible, but only two of 21 collard cultivars were highly susceptible. Most collard cultivars had some resistance, but several collard lines were as resistant as four highly resistant (A-type, monogenic, dominant) cabbage cultivars. Cauliflower cultivars were more susceptible to wirestem than collard or mustard. Rhizoctonia solani anastomosis group (AG) 4 isolates were more virulent on cabbage transplants than AG-2-1 isolates. A new anastomosis group of R. solani, AG-11, was described from Arkansas and Australia. Two populations of R. solani AG-11 from Arkansas differed from each other and from an Australian population. Five bedding plant species reacted variably to binucleate Rhizoctonia fungi used for biocontrol. Impatiens, coleus, and vinca were least affected by pre-emergence damping-off; emerged plants were not affected. Individual bacterial seed treatments applied to wheat were effective in increasing yield at only one of three sites. Natural organic fertilizers used on warm-season turfgrasses on putting greens did not affect quality, clipping weights or root weights over a two-year period.
There were no significant effects of snap bean cultivar on yield or root colonization by Bacillus subtilis. Seedling damping-off, plant stands, yield, and root colonization were significantly affected by seed treatment. Root colonization by B. subtilis increased with the application rate of the supplemental biological but appeared unaffected by seed treatment chemistry. Highest yields of snap beans were obtained with the seed treatment combination of chloroneb plus metalaxyl plus agricultural streptomycin without the supplemental biological. Except for the effects on seedling damping-off, there were no significant interactions between cultivar and seed treatment.
Soil-plant root chambers were developed to identify the oxidative function
associated with virulence of the take-all pathogen Gaeumannomyces graminis
var. graminis. (Ggt). The system permits observation of conversion
of Mn2+ to Mn4+ during pathogenesis.
The importance of microorganisms on micronutrient availability
affecting host resistance and biological control was evaluated by micro-XANES
and XRF spectroscopy techniques. These high energy X-ray fluorescent techniques
study micronutrient element dynamics in different soil environments as
influenced by Ggt and various groups of rhizosphere microorganisms influencing
disease severity. Multiple elements were detected simultaneously, to determine
oxidation states, and obtain data on the spatial distribution of various
nutrient elements around the wheat root and infection court in situ.
Manganese appears to be the predominant biologically influenced micronutrient
influencing the severity of take-all. The XRF scan of the wheat root cell
showed a normal distribution of all elements throughout the soil except
Mn, and established that Mn oxidation is primarily of biological origin.
Gaeumannomyces-like fungi were isolated as the primary oxidizing
fungi and Ggt infestation of cobalt irradiated soil verified Mn oxidation
in association with the fungal hypha. Ggt was reisolated from infested
soils and it's ability to oxidize Mn was verified on MnSO4 agar.
Rhizosphere organisms oxidizing Mn further enhanced Mn oxidation in the
soil while those indicated as Mn reducing on MnSO4 agar were
non-oxidizers in soil. These techniques are powerful new tools to characterize
soil organisms capable of inhibiting the Mn oxidizing virulence factor
of Ggt and thereby provide a mechanism of biological control.
Objective 3. Implementation of management strategies including crop sequences, tillage and other cultural practices to promote biological control with indigenous organisms.
Green hairy vetch residues in soil were found to produce ammonia upon decomposition, which reduced viability of chlamydospores of Thielaviopsis basicola. Populations of Pythium spp. were greater in pepper soils when hairy vetch was incorporated into soil that was then covered with black plastic mulch or killed and left in place as an organic mulch prior to transplanting pepper than in methyl bromide fumigated soil. Percent organic matter colonized by Rhizoctonia solani was greater in the organic mulch treatment than in the other two treatments at 0-5 cm depth, but at 5-10 cm depth, R. solani was greater in both hairy vetch treatments than in fumigated soil. Root rot incidence and severity did not differ among treatments because of dry weather.
Winter cover crops increased populations of Fusarium spp. in soil compared with weedy fallow. Mycorrhizal colonization of vegetation planted during reclamation of surface mine sites was not detected until a full year following reclamation. During the subsequent year, colonization of roots and spore densities increased rapidly and stabilized after two years.
Populations of R. solani were not different following conservation tillage vs. conventional tillage, nor following different winter crops. Populations of R. solani were greater in rotations of grain sorghum compared with wheat, soybean, and cotton. Populations of Pythium spp. were greater in AR than in other states, and greater with hairy vetch than with crimson clover, fallow, wheat, soybean, grain sorghum, or cotton. Mn oxidizers and reducers were greater in GA than MS and OK; reducers were greatest in fallow and least in wheat and reducers were greatest in crimson clover and least in soybean. In GA, root diseases in cotton were more severe following winter crops of crimson clover and sub-clover than following rye, or fallow.
In a sweet corn-snap bean double-crop experiment, conservation tillage decreased populations of total fungi and decreased plant stand compared with conventional tillage. In sweet corn, populations of Pythium spp. and total fungi were increased by poultry litter treatments but R. solani AG-4 populations remained the same. Populations of these three groups in snap bean were not influenced by poultry litter treatments. However, post-emergence damping-off in snap bean was increased with noncomposted broiler liter.
A cover crop study demonstrated that only the residues of a rye winter crop had a lower population of R. solani. Populations of Fusarium spp. and Streptomyces spp. were greater in plots with a cover crop than in weedy fallow plots. Populations of Pythium spp., Bacillus spp., and fluorescent Pseudomonas spp. were not influenced by cover crops. Incidence of sudden death syndrome (SDS) of soybean was significantly lower for no-till than for conventional tillage in a susceptible cultivar. For a resistant cultivar, disease incidence did not differ between the tillage treatments. Sudden death syndrome on soybean was more severe and yield was lower on a susceptible cultivar planted on 76 cm rows than on 19 cm rows. Post-emergence damping-off was increased in cotton planted with conservation tillage into subclover compared with rye or fallow. Pearl millet stubble mulch plus iprodione seed treatment reduced brown spot on white lupin, although these treatments did not reduce Pleiochaeta root rot. However, high soil phosphorus (90 kg/ha) reduced root rot in greenhouse trials. Resistance of corn to stalk rots is lost if the plant is deficient in nitrogen during the grain-fill period. High levels of potassium can suppress nitrogen uptake and increase stalk rot. Cotton stands were 6% lower in a wheat stubble/stale bed system when compared with conventionally planted cotton. In-furrow application of PCNB increased stands in the conservation tillage system, but not in the conventional tillage system.
Tobacco stunt disease was characterized and shown to be caused by the arbuscular mycorrhizal fungus Glomus macrocarpum. This disease was found to be the reason tobacco must be rotated, preferably with tall fescue or another sod crop, in order to maintain the productivity of land for tobacco. These findings raise the suggestion that pathogenic arbuscular fungi are the reason most crops must be rotated to avoid yield decreases. Arbuscular mycorrhizal fungi are widely considered mutualistic with plants, rather than pathogenic to them. However, modern agriculture in developed nations deviates greatly from the conditions under which plants and their fungal symbionts coevolved over millions of years due to practices such as fertilization, continuous cropping of land, and crop monocultures made possible by use of herbicides and cultivation.
Cotton seed treated with either Terraclor Super X EC at 2 or 3 qts pr/A
in-furrow or Prevail HB at 8 or 16 oz/cwt was either planted conventionally
or into a terminated wheat stubble/stale bed system. Stands were significantly
lower in the wheat stubble/stale bed system when compared to conventionally
planted cotton but not in all years. A comparison of fungicide treatment
within each of the tillage systems indicated that commercially treated
seed plus Terraclor Super Xat 2 or 3 qts/A led to significant increases
in cotton stands compared to commercially-treated seed alone in the wheat
stubble/stale bed system. The addition of Prevail HB to commercially treated
seed did not increase stands. In conventionally planted cotton, utilization
of Terraclor Super X or Prevail did not increase stands.
MAJOR PUBLICATIONS SUMMARY OF S-269.
| Publications |
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| Journal Articles . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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| Books . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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| Book Chapters . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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| Experiment Station Publications . . . . . . . . . . . . . . |
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| Other Refereed Publications . . . . . . . . . . . . . . . . . |
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| Patents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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| Abstracts and Proceedings . . . . . . . . . . . . . . . . . . . |
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| Theses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. |
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| Popular articles . . . . . . . . . . . . . . . . . . . . . . . . . . . |
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MAJOR PUBLICATIONS: (Note: joint regional project publications in
boldface)
| An, Z.Q., B.Z. Guo, and J.W. Hendrix. 1998. Viability of soilborne spores of glomalean mycorrhizal fungi. Soil Biol. Biochem. 30:1133-1136. |
| Baird, R.E., T.B. Brenneman, D.K. Bell, D.R. Sumner, N.A. Minton, B.J. Mullinix, and A.B. Peery. 1996. Influence of crop rotation and flutolanil on the diversity of fungi on peanut shells. Phytoprotection 76:101-113. |
| Baligh, M., K.E. Conway, and M.A. Delgado. 1996. Production of ammonium by Pseudomonas cepacia and P. aeruginosa: Quantification and effect on host and pathogen. Recent Res. Develop. in Plant Pathology 1:719. |
| Batson, Jr., W. E., Caceres, J., Benson, M., Cubeta, M.
A., Brannen, P. M., Kenny, D. S., Elliott, M. L., Huber, D. M., Hickman,
M. V., Keinath, A. P., Ownley, B., Newman, M., Rothrock, C. S., Schneider,
R. W., Sumner, D. R., and Thaxton, P. 2000. Efficacy of biological seed
treatments for control of the seedling disease complex of cotton, 1999.
Biol. Cult. Tests 15:31-32.
[S-269 Regional Project publication] |
| Batson, Jr., W. E., Caceres, J., Benson, M., Cubeta, M.
A., Brannen, P. M., Kenny, D. S., Elliott, M. L., Huber, D. M., Hickman,
M. V., Keinath, A. P., Dubose, V., Ownley, B., Canaday, C., Rothrock, C.
S., Schneider, R. W., and Sumner, D. R. 2000. Evaluation of biological
seed treatments for control of seedling diseases of snap bean, 1999. Biol.
Cult. Tests 15:149-150..
[S-269 Regional Project publication] |
| Batson, W. E., Jr., J. Caceres, M. Benson, P.M. Brannen,
M.A. Cubeta, K. Conway, M.L. Elliott, D.M. Huber, A. P. Keinath, M. Newman,
B. Ownley, C.S. Rothrock, R.W. Schneider, C.E. Molsenbocker, D.R. Sumner,
and P. Thaxton. 1999. Biological seed treatments for control of the seedling
disease complex of cotton, 1998. Biol. Cult. Tests 14:25-26.
[S-269 Regional Project publication] |
| Batson, W. E., Jr., J. Caceres, P. Backman, M. Benson, P.M.
Brannen, M.A. Cubeta, M.L. Elliott, D.M. Huber, A.P. Keinath, B. Ownley,
C.S. Rothrock, R.W. Schneider, C.E. Molsenbocker, D.R. Sumner, and P. Thaxton.
1998. Efficacy of biological seed treatments for control of the cotton
seedling disease complex, 1997. Biol. Cult. Tests 13:21-22.
[S-269 Regional Project publication] |
| Batson, W. E., Jr., J. Caceres, P. Backman, M. Benson, P.M.
Brannen, M.A. Cubeta, M.L. Elliott, D.M. Huber, A.P. Keinath, C.S. Rothrock,
R.W. Schneider, C.E. Molsenbocker, and D.R. Sumner. 1998. Efficacy of biological
seed treatments for control of seedling diseases of snap bean, 1997. Biol.
Cult. Tests 13:145-146.
[S-269 Regional Project publication] |
| Batson, W.E., Jr. and J. Caceres. 1997. Influences of conventional and terminated wheat/stale bed systems on the efficacy of seedling disease control strategies. Biol. Cult. Tests 12:28. |
| Batson, W.E., Jr., J. Caceres, M. Benson, P.M. Brannen,
C. Canaday, K. Conway, M.A. Cubeta, M.L. Elliott, J. Fajardo, D.M. Huber,
A.P. Keinath, B. Ownley, C.S. Rothrock, and D.R. Sumner. 1999. Biological
seed treatments for control of seedling diseases of snap bean, 1998. Biol.
Cult. Tests 14:149-150.
[S-269 Regional Project publication] |
| Batson, W.E., Jr., J. Caceres, P. Adams, P. Brannen, K.
Conway, M. Elliott, D. Huber, A. Keinath, C. Rothrock, R. Schneider, C.
Molsenbocker, and D. Sumner. 1997. Efficacy of biological seed treatments
for control of seedlings disease of snap bean, 1996. Biol. Cult. Tests
12:166-167.
[S-269 Regional Project publication] |
| Batson, W.E., Jr., J. Caceres, P.D. Adams, K.E. Conway,
M.L. Elliott, D.M. Huber, A.P. Keinath, C.S. Rothrock, R.W.Schneider, C.E.
Molsenbocker, and D.R. Sumner. 1997. Efficacy of biological seed treatments
for control of the cotton seedling disease complex, 1996. Biol. Cult. Tests
12:26-27.
[S-269 Regional Project publication] |
| Bauske, E.M., P.A. Backman, K.M. Harper, P.M. Brannen, R. Rodríguez-Kábana, and J.W. Kloepper. 1997. Effect of botanical aromatic compounds and seed-surface pH on growth and colonization of cotton plant growth-promoting rhizobacteria. Biocontrol Science and Technology 7: 415-421. |
| Benhamou, N., J.W. Kloepper, A Quadt-Hallmann, and S. Tuzun. 1996. Induction of defense-related ultrastructural modifications in pea root tissues inoculated with endophytic bacteria. Physiological Plant Pathology 112: 919-929. |
| Benhamou, N., J.W. Kloepper, and S. Tuzun. 1998. Induction of resistance against Fusarium wilt of tomato by combination of chitosan with an endophytic bacterial strain: ultrastructure and cytochemistry of the host response. Planta 204: 153-168. |
| Benson, D.M. 1997. Efficacy of two formulations of Gliocladium virens GL-21 for control of Pythium aphanidermatum and Rhizoctonia solani causing damping-off in bedding plants 1994, 1995. Biol. Cult. Tests 12:64. |
| Benson, D.M. and K.R. Barker. 1997. Comparison of Burkholderia cepacia, binucleate Rhizoctonia fungi, and Paecilomyces lilacinus for biocontrol of damping-off, hypocotyl rot, and root-knot nematodes in cotton, 1996. Biol. Cult. Tests 12:25. |
| Boman, R.K., S.L. Taylor, W.R. Raun, G.V. Johnson, D.J. Bernardo, and L.L. Singleton (eds). 1996. The Magruder Plots A Century of Wheat Research in Oklahoma. Agron. Dept. Div. Of Agric. Sci. and Nat. Res., Okla. State Univ. 69pp. |
| Burns, J.R., and D.M. Benson. 2000. Biocontrol of damping-off of Catharanthus roseus caused by Pythium ultimum with Trichoderma virens and binucleate Rhizoctonia fungi. Plant Dis. 84:644-648 |
| Canaday, C. H. 2000. Effects of seed treatment chemicals and Bacillus subtilis on snap bean seedling diseases, pp. 111-117. In: 1999 Vegetable Initiative Progress Report, Univ. of Tennessee Publication No. E11-6515-01-001-00. |
| Candole, B.L., and C.S. Rothrock. 1997. Characterization of the suppressiveness of hairy vetch-amended soil to Thielaviopsis basicola. Phytopathology 87:197-202. |
| Chabot, R., C.J. Beauchamp, J.W.Kloepper, and H.Antoun. 1998. Effect of phosphorus on root colonization and growth promotion of maize by bioluminescent mutants of phosphate solubilizing Rhizobium leguminosarum biovar. phaseoli. Soil Biol. Biochem. 30:1615-1618. |
| Chabot, R., H. Antoun, J.W. Kloepper, and C.J. Beauchamp. 1996. Root colonization of maize and lettuce by bioluminescent Rhizobium leguminosarum biovar. phaseoli. Appl. Environ. Microbiol. 62:2767-2772. |
| Chen, C., D.J. Collins, and G. Morgan-Jones. 1996. Fungi associated with root rot of winter wheat in Alabama. J. Phytopathology 144: 193-196. |
| Chen, C., E.M. Bauske, G. Musson, R. Rodríguez-Kábana, and J.W. Kloepper. 1995. Biological control of Fusarium wilt on cotton by use of endophytic bacteria. Biological Control 5:83-91. |
| Chen, Y., R., Mei, S. Lu, L. Liu, and J. W. Kloepper. 1996. The use of yield-increasing bacteria (YIB) as plant growth-promoting rhizobacteria in Chinese agriculture. In: Management of Soilborne Disease, C. K. Gupta and R.Utkehde, eds. Kalyani Publishers, New Delhi. Pages 165-184. |
| Chun, S.-C. and R.W. Schneider. 1998. Sites of infection by Pythium species in rice seedlings and effects of plant age and water depth on disease development. Phytopathology 88:1255-1261. |
| Chun, S.-C., R.W. Schneider, and M.A. Cohn. 1997. Sodium hypochlorite: Effect of solution pH on rice seed disinfestation and its direct effect on seedling growth. Plant Dis. 81:821-824. |
| Collins, D.J. 1995. Diseases and Pests. In Developing the Potential of Lupin as a Grain and Silage Crop for the Southeastern United States. pp 19-20. Report to the Wheat and Feed Grain Committee. Alabama Agricultural Experiment Station. |
| Conway, K.E. 1996. An overview of the influence of sustainable agricultural systems on plant diseases. Crop Protect. 15:223228. |
| Conway, K.E., N.E. Maness, and J.E Motes. 1997. Integration of biological and chemical controls for Rhizoctonia blight and root rot of rosemary (Rosemarinus officinalis). Plant Disease 82:795-798. |
| Conway, K.E., N.E. Maness, and J.E. Motes 1997. Integration of biological and chemical controls for Rhizoctonia aerial blight and root rot of rosemary. Plant Dis. 81:795-798. |
| Cook, R.J., B.H. Ownley, H. Zhang, and D. Vakoch. 2000. Influence of paired-row spacing and fertilizer placement on yield and root diseases of direct-seeded wheat. Crop Sci. 40:1079-1087. |
| Cook, R.J., B.H. Ownley, H. Zhang, and D. Vakoch. 2000. Influence of paired-row spacing and fertilizer placement on yield and root diseases of direct-seeded wheat. Crop Sci. 40:1079-1087. |
| Creamer, N.G., C.R. Crozier, and M.A. Cubeta. 1999. Influence of seedpiece spacing and plant population on yield, internal quality and economic performance of Atlantic, Snowden and Superior potato varieties in eastern North Carolina. Amer. J. of Potato Res 76:257-262. |
| Crozier, C.R., N.G. Creamer, and M.A. Cubeta. 2000. Role of soil fertility, plant stand and disease on potato yields in eastern North Carolina. Pot. Res. (In Press). |
| Csinos, A.S., W. C. Johnson, A.W. Johnson, D.R. Sumner, R.M. McPherson, and R.D. Gitaitis. 1997. Alternative fumigants for methyl bromide in tobacco and pepper transplant production. Crop Prot. 16:508-594. |
| Cubeta, M. A. and R. Vilgalys. 2000. Rhizoctonia. In Encyclopedia of Microbiology, ed. J. Lederberg, Vol. 4, pp. 109-116, Academic Press, San Diego, CA. |
| Cubeta, M.A., B.R. Cody, R. Sugg, and C.R. Crozier. 2000. The influence of soil calcium, potassium and pH on the development of leaf tipburn of cabbage in eastern North Carolina. Comm. Soil and Plant Anal. 31: 259-275. |
| Datnoff, L. E., S. Nemec, and K. Pernezny. 1995. Biological control of Fusarium crown and root rot of tomato in Florida using Trichoderma harizanum and Glomus intraradices. Biol. Control 5:427-431. |
| de Magalhaes, J.V., M.V.C. Alves, R.F. de Novais, P.R. Mosquim, J.R. Magalhaes, A.F.C. Bahia-Filho, and D.M. Huber. 1998. Nitrate uptake by corn under increasing periods of phosphorus starvation. J. Plant Nutr. 21:753-1763. |
| De Silva, A., K. Patterson, C. Rothrock, and R. McNew. 1999. Phytophthora root rot of blueberry increases with frequency of flooding. HortScience 34:693-695. |
| Dissanayake, N., J.W. Hoy, and J.L. Griffin. 1997. Weed hosts of the sugarcane root rot pathogen, Pythium arrhenomanes. Plant Dis. 81:587-591. |
| Duffy, B.K., B.H. Ownley, and D.M. Weller. 1997. Soil chemical and physical properties associated with suppression of take-all of wheat with Trichoderma koningii. Phytopathology 87:1118-1124. |
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APPLICATION OF RESULTS:
Seedsmen and seed treating organizations now have access to field results across 7 to 10 locations for each of 5 years in the southern region for performance of bacterial and fungal biocontrol agents in control of seedling disease in cotton, snap bean and wheat. The use of a stability analysis has given information on relative performance of specific biocontrol agents such that those that are sensitive to environmental parameters can be separated from those agents that perform well across varying environmental conditions. At cotton test sites two T. virens isolates provided final plant stands equal to the fungicide seed treatments. Pathogens controlled were Pythium or Rhizoctonia. However, the best treatment overall appeared to be a mixture of a fungal and a bacterial biocontrol agent (Trichoderma and Paenibacillus). Plant stand was improved in most cases when biocontrol agents were combined with chemical seed treatment.
In the snap bean trials, over the same 5-yr period at all sites only T. harzianum and Paenibacillus pabuli improved stands over the nontreated control. Laetisaria arvalis slightly reduced stands. Pathogens controlled in snap bean locations were R. solani and Pythium spp. Carboxin significantly increased stand compared to nontreated seed however, not all fungicide seed treatments tested resulted in improved stand.
In addition to examining the effects of seed treatments on plant populations (and so disease control), seed populations of the biological control agents have been examined, both at treatment and at planting, to determine purity and viability. Variability was greatest for the gram-negative bacterial treatments. Seed populations were influenced by rate of application, mixing organisms together, and addition of chemical seed treatments. In all studies, biological seed treatments were compared with standard chemical treatments and a nontreated control.
No benefits have been found with biocontrol agents and disease control in wheat in the southern region, but the number of test sites and entries of biocontrol agents was limited. In some cases, stands in plots of wheat treated with biocontrol agents were actually less than in the nontreated control plots.
Over all crops tested no single biocontrol agent was found that controlled
both Rhizoctonia and Pythium damping-off. Single fungicide seed treatments
also were not consistent across years or location. Growers should be aware
that the most effective seed treatment for cotton and snap bean was a combination
of selected biocontrol agents and one or more fungicides. In addition,
performance of some seed treatment combinations was affected by environment
and thus these would be effective at only favorable locations.
PREPARED BY:
D. Michael Benson, Professor February 20, 2001
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