Progress 09/15/07 to 09/14/10
Outputs
OUTPUTS: This project was initially funded for 2 years, but it was extended for one year without cost. Through this project, one graduate student received her master degree. This project also trained two undergraduate students (one of them is a minority female student) and four visiting international scientists. During this period of three years, we conducted four major experiments to assess the efficacy of the nematode Aphelenchus avenae and the collembolean Hypogastrura perplexa in controlling the disease activities of three fungal pathogens, Pythium ultimum, Rhizoctonia solani, and Phytophthora capsici in greenhouse and transplant crops. 1. Tomato experiment in potting mixtures in greenhouse: This experiment was conducted in the NCSU Phytotron facility to examine the efficiency of faunal controls over Pythium ultimum on tomatoes. Three container media were used by mixing commercial peat moss (Fafard no. 4P) with the dairy cow compost at the rate of 4, 8 and 16 % (v/v). 2. Tomato experiment in field soils: We investigated how the nematode, Aphelenchus avenae and the Collembolan, Hypogastrura perplexa, affected the population dynamics and activity of P. ultimum and R. solani in four organic and three conventional soils, using tomato as a model plant. On each soil, three faunal treatments (nematodes, collembola, and nematodes + collembolan) are designed with one no-faunal control, and one no-pathogen control.. 3. Experiment with bedding plants: Vinca (Catharanthus roseus) and Impatiens (Impatiens balsamina) were grown from seed in the greenhouse and transplanted after seedling emergence (8 days) to 4 inch clay pots. Three soil combinations were used with 4%, 8% and 16 % compost (Daddy Petes Plant Pleaser Dairy Cow Compost) in the potting soil (Fafard 4P). The pots were inoculated with Rhizoctonia solani that had been grown on rice grains and ground up. One week after seedling transplant to the clay pots, the treatments were added to the clay pots. Treatments were 1) Nematode A. avenae, 2) no treatment control, 3) no pathogen control, and 4) fungicide drench. Six weeks after transplanting, seedlings were removed from the pots and disease severity was assessed. Soil from the nematode treatment pots was washed for recovery of nematodes and representative seedlings were assayed for recovery of R. solani. 4. Pepper experiments: We first assessed the effects of multiple species of collembola, mites and nematodes in regulating the population dynamics and pathogenic activity of Phytophthora capsici in three different soils, using pepper-P. capsici as a model plant-pathosystem. We then applied three fungal-feeding animals (nematode Aphelenchus avenae, collembolean Hypogastrura perplexa, and an unidentified mite species) to greenhouse transplant (pepper seedlings) and transplanted these plants to two conventional soils that have recurring problems with P. capsici. 5. In addition, we discovered a mite species that shows high suppressive effects on P. ulitimum and P. capsici. PARTICIPANTS: All Co-PIs:Shuijin HU, David SHEW, Frank LOUWS and Michael BENSON; Research Specialist at NCSU: Cong TU; Graduate Student: Mary Claire G. TAYLOR; International Visitors: Sandra Gacitua ARIAS (University of Concepcion-Chile), Rende QI (Anhui Academy of Agricultural Sciences, China), Fuming DAI (Shanghai Academy of Agricultural Sciences, China), Yi WANG (Northwest A&F University, China); Undergraduate student researchers: Marissa LEE (Swarthmore College), and Hira NIAZ (NCSU). TARGET AUDIENCES: The scientific community: agronomists, ecologists, soil scientists, plant pathologists and students in biological and agricultural sciences; The growers of vegetable and horticultural crops, and organic farmers; Land managers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results obtained in general showed that fungal-feeding mesofauna were effective in suppressing soilborne pathogens and their activities. The population densities of these animals increased in soils and potting mixtures where there were high microbial biomass and activities. The suppressiveness generally correlated with the population density of the fungal-feeding animals. These results enhanced the understanding of the interactions among soilborne fungal pathogens and fungal feeding mesofauna, and may help us design management practices that optimize mesofaunal suppression of soilborne root fungal pathogens and their disease activities. More specifically, 1. Tomato experiments: Results obtained showed that both H. perplexa and A. avenae suppressed the population density and activities of R. solani, P. ultimum and P. capsici. Also, these animals were more effective in organic than conventional soils. Defaunation of the soil eliminated soil suppression to P. ultimum and R. solani in all organic soils and led to high incidence of damping off of tomato seedlings. However, introduction of Aphelenchus avenae into the defaunated soil re-established disease suppression and significantly increased tomato germination rates. In addition, in the mixture of peat moss and compost, the percentage of compost did not significantly affect the efficiency of suppression, although disease suppression tended to be higher in mixtures with high proportions of composts. One manuscript is in preparation for publication for Applied Soil Ecology. 2. Bedding plants experiment: Results from this experiment showed that A. avenae can reduce disease incidence of R. solani on both Vinca (Catharanthus roseus) and Impatiens (Impatiens balsamina). Also, the suppressive efficiency was significantly higher in potting mixtures with 16% compost than the ones with 4% of compost or less and significantly correlated with the numbers of nematodes recovered from the potting mixtures. Nematodes were recovered from all A. avenae-treated pots but the number of nematodes recovered increased with the increasing compost percentage. The pathogen R. solani was successfully re-isolated from representative diseased seedlings taken from pots from each treatment block. One manuscript is in preparation for HortTechnology. 3. Pepper experiment: Our results showed that both H. perplexa and A. avenae can significantly reduced pathogen densities and disease severity by 50% and 80%, respectively. Both animals were most effective in an organically managed soil, possibly because high heterogeneity and high organic matter (and microbial biomass) in this soil allowed both animals to establish and reproduce. Introduction of fungal-feeding mesofauna to transplant crops seedlings increased the suppression to soilborne pathogens and their activities in the new habit after transplanting. One manuscript is in preparation for publication for Phytopathology.
Publications
- Qi R., C. Tu, H. D. Shew, F. Louws, Y. Zhang, J. Ristaino, and S. Hu. 2008. Suppression of Fungal Pathogen Phytophthora capsici by Mycophagous Soil Fauna. 2008 joint meeting of GSA, SSSA, ASA, CSSA, and GCAGS (October 5-9, Houston, Texas).
- Garrison MC, R. Qi , S. Hu, and D. Shew. 2009. Suppression of Phytophthora capsici and Pythium ultimum by the fungal-feeding nematode Aphelenchus avenae. Phytopathology 99:S41. 2009 APS Annual Meeting. August 1-5, 2009 Portland, Oregon.
- Taylor, Mary Claire Garrison, 2010. Mycophagous Soil Fauna for Biological Control of Soilborne Pathogenic Fungi in Greenhouse and Transplant Crops. MS Thesis. North Carolina State University.
- Rende Qi, Cong Tu, H. David Shew, Frank Louws, Mary Claire G. Taylor, Yong Zhang, Greg Hoyt, Jean Ristaino, Shuijin Hu, 2011. Mycophagous faunal suppression of soilborne fungal pathogen Phytophthora capsici in three organic soils. To be submitted to Phytopathology.
- Weijian Zhang, Cong Tu, H. David Shew, Frank Louws, Mary E. Barbercheck, and Shuijin Hu. 2011. Mesofaunal suppression of soil fungal pathogen Pythum ultimum in an organic soil. To be submitted to Applied Soil Ecology.
- Mary Claire G. Taylor, Michael Benson, H. David Shew, Frank Louws, Cong Tu, Shuijin Hu, 2011. Suppression of Pythium ultimum and Rizoctonia solani by the fungal-feeding nematode Aphelenchus avenae in tomato and bedding plants. To be submitted to HortTechnology.
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Progress 09/15/08 to 09/14/09
Outputs
OUTPUTS: Over the past year, we have continued four experiments to assess the efficacy of the nematode Aphelenchus avenae and the collembolean Hypogastrura perplexa in controlling the disease activities of three fungal pathogens, Pythium ultimum, Rhizoctonia solani, and Phytophthora capsici in greenhouse crops. 1. Tomato experiment in potting mixtures in greenhouse: This experiment is conducted in the NCSU Phytotron facility to examine the efficiency of faunal controls over Pythium ultimum on tomatoes. Three container media are used by mixing commercial peat moss (Fafard no. 4P) with the dairy cow compost at the rate of 4, 8 and 16 % (v/v). On each medium, three faunal treatments (nematodes, collembola, and nematodes + collembolan) are designed with one no-faunal control, one fungicide control and one no-pathogen control. 2. Tomato experiment in field soils: We investigated how the nematode, Aphelenchus avenae and the Collembolan, Hypogastrura perplexa, affected the population dynamics and activity of P. ultimum and R. solani in four organic and three conventional soils, using tomato as a model plant. The field soils were also defaunnated (65oC for three hours, twice over three days) to assess the roles of native animals in pathogen and disease suppression. 3. Experiment with bedding plants: Vinca (Catharanthus roseus) and Impatiens (Impatiens balsamina) were grown from seed in the greenhouse and transplanted after seedling emergence (8 days) to 4 inch clay pots. Three soil combinations were used with 4%, 8% and 16% compost (Daddy Petes Plant Pleaser Dairy Cow Compost) in the potting soil (Fafard 4P). The pots were inoculated with Rhizoctonia solani that had been grown on rice grains and ground up. One week after seedling transplant to the clay pots, the treatments were added to the clay pots. Treatments were 1) Nematode Aphelenchus avenae at a rate of ~ 2000 nematodes per clay pot, 2) no treatment control, 3) no pathogen control, and 4) fungicide drench. Six weeks after transplant, seedlings were removed from the pots and disease severity was assessed. Soil from the nematode treatment pots was washed for recovery of nematodes and representative seedlings were assayed for recovery of R. solani. This experiment will be repeated with both the nematodes and the collembolean Hypogastrura perplexa in the Spring, 2010. 4. Pepper experiments: We first assessed the roles of collembolans and nematodes in regulating the population dynamics and pathogenic activity of Phytophthora capsici in three different soils, using pepper-P. capsici as a model plant-pathosystem. Both collembolans and nematodes were significantly reduced P. capsici populations and disease severity, particularly in an organic soil. We are currently expanding this study to four conventional soils and four organic soils. The conventional soils, two from the coastal area and other from the Mountainous regions of NC have recurring problems with P. capsici. PARTICIPANTS: In addition to the PI and three co-PIs, Miss Mary Clarie Garrison has been working on this project full time, and Dr. Cong Tu worked on this project for about 2 months in the past year. Also, Miss Hira Niaz has joined this project through an undergraduate research project. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
1. Tomato experiments: Our results obtained so far have showed that both H. perplexa and A. avenae suppressed the population density and activities of R. solani, P. ultimum and P. capsici. Also, these animals were more effective in organic than conventional soils. Defaunation of the soil eliminated soil suppression to P. ultimum and R. solani in all organic soils and led to high incidence of damping off of tomato seedlings. However, introduction of Aphelenchus avenae (at a rate of 4000 individuals per kg-1 soil) into the defaunated soil re-established disease suppression and significantly increased tomato germination rates. In addition, in the mixture of peat moss and compost, the percentage of compost did not affect the efficiency of suppression. One manuscript is in preparation for publication for Soil Biology & Biochemistry. 2. Bedding plants experiment: Nematodes were recovered from all A. avenae-treated pots with an average of ~850 nematodes per pot. The pathogen R. solani was successfully re-isolated from representative diseased seedlings taken from pots from each treatment block. Results from this experiment showed that A. avenae can reduce disease incidence of R. solani on both Vinca (Catharanthus roseus) and Impatiens (Impatiens balsamina). More samples are being analyzed. 3. Pepper experiment: Our results showed that both H. perplexa and A. avenae can significantly reduced pathogen densities and disease severity by 50% and 80%, respectively. Both animals were most effective in an organically managed soil, possibly because high heterogeneity and high organic matter in this soil allow both animals to establish and grow. One manuscript is in preparation for publication for Plant Disease.
Publications
- Garrison MC, R.Qi , S. Hu, and D. Shew. 2009. Suppression of Phytophthora capsici and Pythium ultimum by the fungal-feeding nematode Aphelenchus avenae. Phytopathology 99:S41. 2009 APS Annual Meeting. August 1-5, 2009 Portland, Oregon.
- Qi R., C. Tu, H. D. Shew, F. Louws, Y. Zhang, J. Ristaino, and S. Hu. 2008. Suppression of Fungal Pathogen Phytophthora capsici by Mycophagous Soil Fauna. 2008 joint meeting of GSA, SSSA, ASA, CSSA, and GCAGS (October 5-9, Houston, Texas).
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Progress 09/15/07 to 09/14/08
Outputs
OUTPUTS: We first identified a graduate student for this project. Mary Claire Garrison has joined the project in January, 2008. We also assigned Dr. Cong Tu (research specialist supported by NCSU) to work on this project part time. We have conducted or are carrying out four experiments to determine the efficacy of the nematode Aphelenchus avenae and the collembolean Hypogastrura perplexa in controlling the disease activities of three fungal pathogens, Pythium ultimum, Rhizoctonia solani, and Phytophthora capsici in greenhouse crops. 1. Feeding preference experiment: A preliminary experiment examining fungal feeding preference of the tested nematodes (Aphelenchus avenae) and collembolla (Sinella curviseta and Hypogastrura perplexa) has been conducted on Petri dishes. The test fungal species included five common plant pathogens (Phytophtora capsici, Pythium aphanidermatum, Furasium oxysporum, Pythium ultimum and Rhizoctonia solani), non-pathogenic Rhizoctonia solani and biocontrol agent Trichoderma harzianum. These fungi were grown in 12-cm Petri dish in various combinations and were not directly in contact when the test animals were introduced. The testing animals were placed at the center of the Petri dish. The movement of the introduced animals was monitored over the time and the total number of animals on the mycelium of each pathogen was recorded. 2. Pepper experiment: We have evaluated the roles of collembolans and nematodes in regulating the population dynamics and pathogenic activity of Phytophthora capsici in three different soils, using pepper-P. capsici as a model plant-pathosystem. Soils were defaunated, and then inoculated with P. capsici, collembola (Hypogastrura perplexa or Sinella curviesta), and nematodes (Aphelenchus avenae) in various combinations. Pepper seeds were planted one week after pathogen inoculation, and the seedling mortality was then examined weekly. Pathogen density and faunal populations were assessed 21 days after seeding. 3. Tomato experiment: This experiment is conducted in the NCSU Phytotron facility to examine the efficiency of faunal controls over Pythium ultimum on tomatoes. Three container media are used by mixing commercial peat moss (Fafard no. 4P) with the dairy cow compost at the rate of 4, 8 and 16 % (v/v). On each medium, three faunal treatments (nematodes, collembola, and nematodes + collembolan) are designed with one no-faunal control, one fungicide control and one no-pathogen control. 4. Bedding plants experiment: This experiment evaluates the effects of the nematode Aphelenchus avenae and the collembolean Hypogastrura perplexa on pathogen Rhizoctonia solani, using Impatiens (Impatiens balsamina-Super Elfin White) and vinca (Catharanthus roseus -Peppermint Cooler) as model plants. This experiment is under way in the NCSU greenhouses on the Method Road. Impatiens and vinca plugs have been purchased and will be transplanted to 6-cell packs with a peat moss based medium (Fafard no. 4P potting mix amended with 4% dairy cow compost). PARTICIPANTS: Mary Claire Garrison: MS Graduate student; Cong Tu, PhD, Research Specialist; Shuijin Hu, PI, associate professor, NCSU; David Shew, Co-PI, professor, NCSU; Frank Louws, Co-PI, associate professor, NCSU; Michael Benson, Co-PI, professor, NCSU TARGET AUDIENCES: Farmers and growers of vegetables and oramental crops; Scientific community in general: particularly plant pathologists,soil scientists,ecologists and crop scientists; Students in agricultural and environmental sciences PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
1. Feeding preference experiment: The results obtained so far have showed that these animals favor non-pathogenic and pathogenic Rhizoctonia solani over Pythium ultimum, and avoid Furasium oxysporum and Trichoderma harzianum. These results indicate that these fungal-feeding animals may selectively suppress fungal pathogens and their activities. 2. Pepper experiment: The number of H. perplexa significantly increased by up to 41-fold, but the magnitude of the increase was found to be lower in the clay soil than in the sandy and loamy ones. The population of A. avenae significantly increased in both the clay soil and the sandy loam, but not in the loamy soil. Compared to the non-faunal control, introducing soil animals reduced the population of P. capsici by between 50 to 85%. Soil fauna significantly reduced disease incidence on pepper and soil type significantly affected the efficiency of faunal suppression. These results suggest that soil mesofauna might be managed for suppression of seedling diseases caused by soilborne pathogens in field.
Publications
- Rende Qi, Cong Tu, H. David Shew, Frank Louws, Yong Zhang, Jean Ristaino, and Shuijin Hu. 2008. Suppression of Fungal Pathogen Phytophthora capsici by Mycophagous Soil Fauna. 2008 joint meeting of GSA, SSSA, ASA, CSSA, and GCAGS (October 5-9, Houston, Texas).
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