2007 Annual Report 1a.Objectives (from AD-416) The overall objective of this cooperative research project is to reduce root and bulb rot and vascular wilt disease losses in greenhouse floriculture. Specific objectives include:. 1)Tracking isolates of Pythium spp. within flower production greenhouses with the goal of refining and focusing integrated management actions,. 2)Enhancing our knowledge of the etiology of Phytophthora diseases of floriculture crops,. 3)Developing a better understanding of biological and cultural factors that affect pathogenicity of root rot, bulb rot, and vascular wilt pathogens and the development of the diseases they cause, and. 4)Developing new tools for management of root rot, bulb rot, and vascular wilt diseases of floriculture crops. 1b.Approach (from AD-416) Project objectives will be accomplished through establishment of an interdisciplinary research team bringing together the skills of plant and insect pathologists, plant pathologists, plant physiologists, and greenhouse horticulturists. Root rot, bulb rot and vascular wilt diseases cause significant losses of floricultural crops year after year, and often sharply reduce crop quality. For common greenhouse resident pathogens such as Pythium, knowing the species identity and the population from which the pathogen came are crucial pieces of information needed to trace the organism to its origin in the production facility and then to formulate an effective management strategy. We propose to use molecular methods to track the source of epidemics in order to develop appropriately-directed management strategies. In addition to this focus on Pythium monitoring within the greenhouse, planned research will provide a better understanding of biological and cultural factors that affect pathogenicity of root rot, bulb rot, and vascular wilt pathogens and the development of the diseases they cause. This information will be used to improve existing disease management technologies and strategies and enable their incorporation into integrated greenhouse pest management systems. 3.Progress Report Unique genetic sequence found to identify a specific Fusarium strain. Currently there is no reliable, rapid assay to assess inoculum levels of specific Fusarium pathogens that cause basal rot in bulb crops. Traditional agar culture of soil samples does not distinguish between the different taxa of F. oxysporum. Studies conducted by subcontractee Dr. Gary Chastagner of Washington State University developed IGS (intergenic spacer) sequences for pathogens specific to various bulb crops and spinach. Sequence alignments failed to reveal any unique polymorphisms among the bulb formae speciales but did identify a single nucleotide polymorphism (SNP) unique to F. oxysporum f. sp. spinaciae. This work will be continued, examining other regions of the Fusarium genome, to develop techniques to help bulb growers assess the inoculum in particular fields or in planting stock prior to planting. Phytophthora diseases identified in herbaceous perennial and bulb crops. Crop surveys and diagnoses conducted from 2004 to 2006 by Margery Daughtrey and coworkers at Cornell’s Long Island Horticultural Research & Extension Center indicated an increase in diseases on herbaceous perennials due to Phytophthora nicotianae and P. drechsleri; these same pathogens have also been problematic in greenhouse crops in recent years. Daughtrey and subcontractee Steven N. Jeffers of Clemson University have identified Phytophthora root rot of tulip, a disease new to the USA, in June 2007. Tests to confirm the identification of P. porri, not previously reported in the US, are underway. Other Phytophthora species identified on ornamentals were P. capsici, P. cinnamomi, P. citricola, P. citrophthora, P. cryptogea, P. drechsleri, P. nicotianae and P. palmivora. Activities of this project have been monitored by the ADODR through communication with the Project PI, M. Daughtrey, of the Cornell University Department of Plant Pathology. Project activities at the Long Island Horticultural Research & Extension Center are monitored via meetings at Cornell, meetings at professional conferences, and by telephone conversations; activities at Cornell’s Department of Horticulture (Project Co-PI W. B. Miller) are monitored through discussion at meetings on campus. PI M. Daughtrey discusses progress with subcontractees (researchers at Penn State, Clemson, and Washington State Universities) throughout the year by phone and during professional meetings and visits, and communicates this information to the ADODR. Peer-reviewed scientific publications authored by project collaborators Garzon, C. D., Yanez, J. M., Moorman, G. W. 2007. Pythium cryptoirregulare, a new species within the P. irregulare complex. Mycologia 99:291-301. Suazo, G. J., W. B. Miller, Bergstrom, G. C. 2007. Ethylene production by Fusarium oxysporum f. sp. tulipae in live bulbs and in vitro using freeze dried tulip bulb powder. HortScience 42(4):890. 4.Accomplishments Genetic markers identified that allow tracking of Pythium strains in greenhouses. Earlier efforts to reliably fingerprint Pythium strains were not entirely successful, so until now we have not been able to track the movement of individual pathogen strains throughout the greenhouse. In 2007, subcontractee Dr. Gary Moorman at Penn State University developed simple sequence repeat (SSR) markers for Pythium aphanidermatum, P. irregulare and P. cryptoirregulare. Fourteen SSR primer pairs are now available for the destructive poinsettia and chrysanthemum pathogen, P. aphanidermatum, and 21 and 22 primers for the other two species, respectively. This technique will be a very helpful tool to identify infection venues. Laboratories assisting growers will be able to use this technique to tell the difference between lapses in greenhouse sanitation and newly-introduced pathogens. NP 303 (Plant Diseases), Component 1 (Disease Diagnosis: Detection, Identification, and Characterization of Plant Pathogens), Problem Statement 1A (New Diagnostic Methods and Tools). Important new Pythium species identified. A publication was accepted naming a new Pythium species of significance to the greenhouse industry: Pythium cryptoirregulare is a new species previously hidden within what had been called Pythium irregulare. DNA sequencing and DNA fingerprinting studies in Dr. Moorman’s lab at Penn State led to this discovery, by separating two species that were morphologically identical. The new species is important to growers because while none of the P. irregulare isolates are resistant to mefenoxam (active ingredient in the fungicide SubdueMAXX), many P. cryptoirregulare isolates are resistant. NP 303 (Plant Diseases), Component 1 (Disease Diagnosis: Detection, Identification, and Characterization of Plant Pathogens), Problem Statement 1B (Detection, Identification, Characterization, and Classification of Pathogens). Tulip cultivars found to vary in ethylene production when infected by Fusarium. Fusarium disease effects on tulip bulbs cause large dollar losses during shipment around the globe. Dr. William B. Miller at Cornell University has confirmed preliminary studies indicating a wide variation in the ethylene production of different tulip cultivars diseased with Fusarium, as well as an effect of fungus strain. Approximately half of the assayed cultivars produced more than the published (baseline) levels of ethylene, and half produced less. About 20 per cent of the tulip cultivars give off very low levels of ethylene when infected by Fusarium. Learning more about ethylene production by Fusarium in diseased bulbs will ultimately lead to improved handling and storage of tulips. NP 303 (Plant Diseases) Component 2 (Biology, Ecology, Epidemiology, and Spread of Plant Pathogens and Their Relationships with Hosts and Vectors), Problem Statement 2A (Pathogen Biology, Virulence Determinants, and Genetics of the Pathogen). New experimental technique developed for studying Fusarium disease of tulips. Studying cultivar effects on Fusarium disease in tulips has previously required whole-plant studies. Dr. Miller and coworkers at Cornell University have developed an in vitro system utilizing freeze-dried tulip bulb powders as the sole carbon source for Fusarium growth. This system will allow researchers to study specific differences in tulip cultivars’ ability to support ethylene production by Fusarium. NP 303 (Plant Diseases), Component 2 (Biology, Ecology, Epidemiology, and Spread of Plant Pathogens and Their Relationships with Hosts and Vectors), Problem Statement 2A (Pathogen Biology, Virulence Determinants, and Genetics of the Pathogen). Phos acids and Disarm found to control Thielaviopsis and Phytophthora diseases. Both the fungus Thielaviopsis basicola and the oomycete Phytophthora nicotianae cause lethal root and crown disease on pansies. Trials at Cornell’s Long Island Horticultural Research and Extension Center conducted by M. Daughtrey showed that treatments with the phosphorous acid materials Aliette and Alude, as well as the experimental material Disarm, protected plants against stunting and other symptoms of both of these pathogens. These results indicated a surprising benefit of phosphorous acid materials against Thielaviopsis. Growers of pansy, viola, petunia, catharanthus and calibrachoa, in particular, will find materials with broad effectiveness against Thielaviopsis and Phytophthora especially beneficial, since these crops are vulnerable to both pathogens. NP 303 (Plant Diseases) Component 4 (Biological and Cultural Strategies for Sustainable Disease Management), Problem Statement 4A (Biological and Cultural Control Technologies). Susceptibility of bedding plants to a devastating landscape disease evaluated. Severe losses caused by the oomycete Phytophthora nicotianae have been seen in landscape plantings of bedding plants, especially Wave petunias, in the southern USA in recent years. A trial established by Steven Jeffers at Clemson University in June 2007 compared 12 Wave petunia cultivars as well as other popular bedding plant species for their susceptibility to P. nicotianae. Results confirmed earlier findings that different strains of this pathogen specialize (exhibit greatest virulence) against different host plants. Results will help home gardeners, commercial growers and landscape gardeners to choose more resistant cultivars for use in areas contaminated with this destructive pathogen, eliminating the need for protective fungicide applications. NP 303 (Plant Diseases), Component 3 (Plant Disease Resistance), Problem Statement 3B (Disease Resistance in New Germplasm and Varieties). Reduced risk fungicides found to work well against bulb diseases. Identification of effective “reduced risk” fungicides is needed by bulb growers. Flutolanil and fludioxonil treatments were as effective as PCNB in controlling gray bulb rot on tulips in tests by Dr. Gary Chastagner at Washington State University. In-furrow flutolanil applications did not adversely affect the growth of the three cultivars of tulip tested. Also, bulb dips in pyraclostrobin, pyraclostrobin plus boscalid, or azoxystrobin provided better control of blue mold on irises and tulips than the industry standard. This information will be incorporated into product labels and will be adopted by growers in the future. NP 303 (Plant Diseases), Component 4 (Biological and Cultural Strategies for Sustainable Disease Management, Problem Statement 4A (Biological and Cultural Control Technologies). 5.Significant Activities that Support Special Target Populations Results from several studies presented here and in the previous reports have been presented to growers and extension personnel. Many greenhouse and nursery operations are classified as small farms (< $250,000 annual gross receipts), and it is anticipated that the accomplishments reported thus far will ultimately translate into improved crop management recommendations and techniques that will benefit this and all grower groups. 6.Technology Transfer Number of web sites managed 2 Number of non-peer reviewed presentations and proceedings 21 Number of newspaper articles and other presentations for non-science audiences 10