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Terence L. Robinson and William C. Johnson

Rootstock breeding programs in the United States, the United Kingdom, Germany, Russia, Poland, the Czech Republic, and Japan have all released apple rootstocks in the recent past that are potentially important to the worldwide apple industry in the next century. Several of these programs are continuing to breed new rootstocks. Each program has focused on different breeding objectives, thus giving a wide range of horticultural characteristics among this new group of rootstocks. All programs have focused on the horticulturally important traits of productivity, dwarfing and precocity but certain programs have also emphasized other characteristics such as propagability, stress tolerance, disease resistance or insect resistance. Commercialization of this new group of rootstocks is proceeding at an extremely fast pace due to the worldwide networking of fruit tree nursery companies and the use of plant patents. This presents a large job for research and extension personnel to properly test rootstocks for adaptability to different growing areas before they are planted on a large scale. The national rootstock testing project (NC-140) composed of researchers from most apple growing states and provinces in the U.S. and Canada is collecting rootstocks from around the world and conducting uniform field trials that give performance data from a wide variety of climates and soils. This information becomes the basis for local rootstock recommendations in North America. This presentation reviews the most promising rootstocks from around the world and summarize the research information from North American and worldwide trials.

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Thomas C. Holt, Brian K. Maynard and William A. Johnson

Degraded water quality is a growing concern across the northeast and in many cases may be linked back to agricultural operations as nonpoint sources of nitrate and phosphorous pollution. Constructed wetlands have emerged as effective, low-cost methods of water treatment that have the potential to reduce agricultural nonpoint source pollution and contribute to agricultural sustainability. However, the costs of implementing treatment wetlands as a BMP are high, with little opportunity for cost recovery. We have initiated, at a wholesale plant nursery in Rhode Island, an economical solution to treating nursery runoff that incorporates into a treatment wetland the wholesale production of native and ornamental wetland plants. Our goal is to demonstrate how nursery growers may produce a high-demand crop while addressing nonpoint source pollution on their land. Over the next few years, we will evaluate the economic impact of converting nursery production space into treatment wetland production space. We also will research the feasibility of enclosing treatment wetlands in passively heated polyhouses to facilitate the year around treatment of agricultural runoff. Information gathered from both the on-farm demonstration and research sites will be extended to farmers and other agricultural businesses or professionals through outreach programming. The theory, objectives, and construction of the demonstration treatment-production wetland will be presented.

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Thomas C. Holt, Brian K. Maynard and William A. Johnson

We assessed the capacity for nutrient removal of ornamental water garden plants being grown in treatment-production wetland biofilters. Plant biomass, nutrient uptake, tissue nutrient content, and production potential were compared for five popular ornamental water garden plant species: Typha latifolia L., Iris pseudacorus L., Phalaris arundinacea L. `Picta', Canna glauca L., and Colocasia esculenta (L.) Schott. Plants were grown in triplicate 0.3 m2 × 0.3 m, deep gravelbed mesocosms fed with 20N-20P-20K Peter's fertilizer (Scotts-Sierra Horticultural Products Co., Marysville, Ohio) reconstituted to 100 ppm N. After 120 days, mean species total biomass ranged from 1.4 to 5.6 kg·m -2, while producing 105 to 206 divisions per square meter. Growth for Canna and Colocasia was greatest, while Typha produced the most divisions. Mean tissue N and P concentrations ranged from 18 to 29 and 2.1 to 3.0 mg·g -1, respectively. Maximum plant accumulation of 144 g N/m 2 and 15.6 g P/m2 accounted for 70% of the N and 15% of the P supplied by fertilizer. Mean removal of total N and P ranged from 42% to 90% and 18% to 58%, respectively, and was positively correlated with plant biomass. Nutrient removal ability was ranked as Canna = Colocasia > Typha > Iris = Phalaris.

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William C. Johnson, Phil L. Forsline, Herb S. Aldwinckle, William C. Johnson, Phil L. Forsline, H. Todd Holleran, Terence L. Robinson and John J. Norelli

In 1998, the USDA-ARS and Cornell Univ. instituted a cooperative agreement that mobilized the resources for a jointly managed apple rootstock breeding and evaluation program. The program is a successor to the Cornell rootstock breeding program, formerly managed by Emeritus Professor of Horticultural Sciences James N. Cummins. The agreement broadens the scope of the program from a focus on regional concerns to address the constraints of all the U.S. apple production areas. In the future, the breeding program will continue to develop precocious and productive disease-resistant rootstock varieties with a range of vigor from fully dwarfing to near standard size, but there will be a renewed emphasis on nursery propagability, lodging resistance, tolerance to extreme temperatures, resistance to the soil pathogens of the sub-temperate regions of the U.S., and tolerance to apple replant disorder. The program draws on the expertise available at the Geneva campus through cooperation with plant pathologists, horticulturists, geneticists, biotechnologists, and the curator of the national apple germplasm repository. More than 1000 genotypes of apple rootstocks are currently under evaluation, and four fire blight- (Erwinia amylovora) resistant cultivars have been recently released from the program. As a service to U.S. apple producers, rootstock cultivars from other breeding programs will also be evaluated for productivity, size control, and tolerance to a range of biotic and abiotic stress events. The project will serve as an information source on all commercially available apple rootstock genotypes for nurseries and growers.

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William C. Johnson, William C. Johnson, Martin Goffinet, Mary J. Welser, Terence L. Robinson, H. Todd Holleran, Karl J. Niklas and Steve A. Hoying

An increased incidence of graft union failure of apple trees during high wind events has been noted by researchers participating in the NC-140 regional rootstock testing project for certain rootstock-scion combinations. By measuring the strength of graft unions in a survey of mature apple trees in multiple stock-scion combinations, we have determined that there are significant differences. These differences may be attributable to genotype specific characteristics of rootstocks, scions, and/or rootstock-scion interactions. We are presently exploring potential biophysical and anatomical differences related to weak graft unions of apple rootstock and scion varieties. As traits correlated with weak graft unions are identified, they will be useful to help growers avoid the rootstock-scion combinations that are particularly susceptible to tree failure.