Identification of Winter Habit Bread Wheat Landraces in the National Small Grains Collection with Resistance to Emerging Stem Rust Pathogen Variants

Wheat stem rust caused by Puccinia graminis f. sp. tritici (Pgt) is a widespread and recurring threat to wheat production. Emerging Pgt variants are rapidly overcoming major gene resistance deployed in wheat cultivars and new sources of race-nonspecific resistance are urgently needed. The National Small Grains Collection (NSGC) contains thousands of wheat landrace accessions that may harbor unique and broadly effective sources of resistance to emerging Pgt variants. All NSGC available facultative and winter-habit bread wheat landraces were tested in a field nursery in St. Paul, MN against a bulk collection of six common U.S. Pgt races. Infection response and severity data were collected on 9,192 landrace accessions at the soft-dough stage and resistant accessions were derived from single spikes. Derived accessions were tested in St. Paul a second time to confirm resistance and in a field nursery in Njoro, Kenya against emerging races of Pgt with virulence to many known resistance genes including Sr24, Sr31, Sr38, and SrTmp. Accessions resistant in the St. Paul field were also tested at the seedling stage with up to 13 Pgt races, including TTKSK and TKTTF, and with 19 molecular markers linked with known stem rust resistance genes or genes associated with modern breeding practices. Forty-five accessions were resistant in both U.S. and Kenya field nurseries and lacked alleles linked with known stem rust resistance genes. Accessions with either moderate or strong resistance in the U.S. and Kenya field nurseries and with novel seedling resistance will be prioritized for further study.

Investigation of two native Australian perennial forage legumes for their potential use in agriculture: Indigofera australis subsp. hesperia and Glycyrrhiza acanthocarpa

In order to investigate the potential for domestication of native pasture legumes, a seed collecting mission was undertaken between Kalbarri and Esperance in the south of Western Australia followed by establishment of a field nursery at Northam, Western Australia. Indigofera australis subsp. hesperia Peter G.Wilson & Rowe was collected from eight sites, Indigofera brevidens Benth. from one site, and Glycyrrhiza acanthocarpa (Lindl.) J.M.Black from six sites. The field nursery was an irrigated, replicated trial designed to produce seed for future field testing and to provide preliminary information on plant agronomic characteristics. Over 12 months, I. australis produced herbage dry matter (DM) of 2.1–4.4 t/ha compared with 3.4 t/ha for a composite line of tedera (Bituminaria bituminosa C.H. Stirton vars. albomarginata and crassiuscula) and 1.0 t/ha DM for G. acanthocarpa. Most lines had digestibility and crude protein (15–25%) values that would support moderate growth of sheep or cattle. The best line of G. acanthocarpa produced >400 kg/ha of seeds, whereas I. australis had poor production most likely due to poor adaptation to the nursery site. The severity of cutting of I. australis plants had no significant effect on visual assessments of herbage growth. Most plants of I. australis died within 3 years, whereas most plants of G. acanthocarpa, I. brevidens and tedera survived for 3 years. Both I. australis and G. acanthocarpa have potential for use in broadacre agriculture as grazing plants, most likely in niches specifically suited to each, and demonstrate that native plants can contribute to pasture production currently dominated by exotic species.

The Economic Impact of Paraffin Type and Substrate Mixture on the Production of Grafted Vines—Case Study Muscat Ottonel

The study focussed on a nursery by analyzing its strategic choices to obtain the best profit on grapevine planting material. The production of grapevine grafts involves high labor and material costs. In this study, Muscat Ottonel grape variety grafted on Oppenheim Sellection 4 rootstock was paraffined with different types of wax: standard wax (SW), paraffin with 8-chinolinol (8C) and paraffin with oxiquinolein (OX) (before callusing), and silver color (S), blue color (B) and standard (SW) paraffin (after grafting callusing and before planting in field nursery). After uprooting from the field nursery, all variants were paraffined with red paraffin for storage. The unit cost price was calculated based on total expenses and the yield of grafts obtained in the vine field nursery. The lowest price per unit cost was recorded for the 8C/S variant, directly related to the first quality yield after uprooting from the nursery. The highest profit rate was for the 8C/S variant, while the lowest was registered to the SW/SW variant. The grafts of the 8C/S variant were potted in three rooting mixtures. Variant B (forest ground 60% + black peat 25% + river sand 10% + conifer sawdust 5%) generated the highest yield of the potted grafted vine with a rate of profit of over 170%, due to the lower production cost and high yield of potted vines, while variant C (forest ground 70% + river sand 15% + conifer sawdust 15%), determinate the lowest yield. Results may be useful in orienting the small-to-medium grapevine planting materials producers to choose the best cooperative strategies, which nurseries might implement to enhance their competitiveness and survive in the long-run.

Changes in Tree Root Architecture Resulting from Field Nursery Production Practices1

Nursery production practices subject tree root systems to mechanical and environmental factors that are not imposed on plants regenerated naturally from seed. Architecture of undisturbed root systems of nine trees species commonly planted in urban landscapes was compared to root architecture of these tree species produced using common field nursery production practices. When young nursery production seedlings are root-pruned prior to replanting, the loss of the lower portion of the main root and lateral roots emerging from it, and initiation of adventitious roots from the cut end, alter the root system architecture. Nursery production plants have 7 to 48 percent fewer natural lateral roots that could develop into flare roots than undisturbed plants. New roots initiated from the cut end of the main root on nursery production plants can substitute for the loss of lateral roots, if accepted practices are followed. Root architecture of trees is established early. With minor exceptions attributed to the loss of small roots less than 1 mm diameter, there were no significant changes in the number of lateral roots over the 4 year period in both nursery production and undisturbed plants. This consistent number of roots also suggests that pruning the main root did not stimulate additional lateral roots above the pruning cut. Root architecture of liner stock produced in nurseries can be equivalent to undisturbed root systems. Index words: Structural roots, root pruning, bare root, root depth, taproot, root flare. Species used in this study: Norway maple (Acer platanoides L.); green ash (Fraxinus pennsylvanica Marsh.); littleleaf linden (Tilia cordata L.); red maple (Acer rubrum L.); European white birch (Betula pendula Roth.); Kentucky coffee tree (Gymnocladus dioicus L.); domestic apple (Malus spp.); red oak (Quercus rubra L.); Siberian elm (Ulmus pumila Jacq.).

Impact of Cover Crop Usage on Soilborne Diseases in Field Nursery Production

Soilborne pathogens are a significant economic problem for nursery production in the Southeastern United States. The goal of this study was to determine the impact of cover crops on soilborne disease suppressiveness in such systems. Soils from red maple (Acer rubrum L.) plantation fields grown with and without cover crops were sampled, either while the cover crops were growing (pre-disked) or post-season, following cover crop incorporation into the soil (post-disked). Greenhouse bioassays were conducted using red maple seeds on inoculated (with Rhizoctonia solani (J.G. Kühn) or Phytophthora nicotianae (Breda de Haan)) and non-inoculated field soils. The damping-off, root rot disease severity, percent recovery of Rhizoctonia and Phytophthora, and pseudomonad population were examined during the two years of the experiment. Results showed that cover crop incorporation was beneficial for inducing disease supressiveness characteristics of soil. Cover crop incorporation into the soil significantly or numerically reduced disease severity and pathogen recovery in infested soil compared to the bare soil treatment. Cover crop incorporation was found to be partially associated with the reduction of seedling damping-off. The pseudomonad microbial population was greater when cover crop was present, and is thought to be antagonist to soilborne pathogens. Therefore, cover crops can be integrated in field nursery production systems to suppress soilborne pathogens.

Thielaviopsis Trunk Rot of Palm

Thielaviopsis paradoxa is a fungus that can infect any part of a palm, and so can cause numerous diseases. In Florida, the two most frequent (and usually lethal) Thielaviopsis diseases observed in the landscape and field nursery are a bud (heart) rot and trunk rot. Thielaviopsis bud rot is discussed at http://edis.ifas.ufl.edu/pp144. This document is PP-219, one of a series of the Plant Pathology Department, UF/IFAS Extension. Original publication date January 2006. PP-219/PP143: Thielaviopsis Trunk Rot of Palm (ufl.edu)

Experimental Nets for a Protection System against the Vectors of Xylella fastidiosa Wells et al.

The effectiveness of experimental nets in preventing the access of adult meadow spittlebug Philaenus spumarius L., the main vector of Xylella fastidiosa Wells et al. subspecies pauca, sequence type (ST) 53, in olive tree nurseries and orchards was evaluated. To optimize the net design, mesh size, kind of fabric, thread typology, and radiometric properties, six nets with different mesh sizes and kinds of fabric were evaluated in laboratory and in field experiments. Laboratory bioassays evaluating the capability of adult spittlebugs to pass through nets with different mesh sizes (1.2, 1.8, 2.4 mm) showed that all nets with a mesh size equal to or lower than 2.4 mm prevented insect crossing. These results were confirmed in field conditions using an experimental net box apparatus. Further laboratory tests showed a positive correlation between porosity and radiometric properties of the nets. Three prototypes of thermally stabilized flat woven nets made of circular cross-sectional yarns, knitted net with strips, and knitted nets made of yarns were tested after the evaluation of their potential usability in terms of porosity stability. The knitted net features were found to be the most suitable. The net transmissivity of the total and direct component of solar radiation in the photosynthetically active radiation and the infrared ranges increased with the net porosity. A prism-shaped wooden frame with a triangular base covered with the knitted net with a 2.4 mm mesh confirmed the insect’s capability of reaching considerable heights, up to 2.85 m. Hence, based on our results, the monowire knitted net with a 2.4 mm mesh can be used in open field nursery and olive orchards to prevent the access of P. spumarius adults and to shield the openings of greenhouse nurseries.

Comparative Water and Nutrient Application Rates among Ornamental Operations in Maryland

Quantifying the range of fertilizer and irrigation application rates applied by the ornamental nursery and greenhouse industry is challenging as a result of the variety of species, production systems, and cultural management techniques that are used. To gain a better understanding of nutrient and water use by the ornamental industry in Maryland, 491 potential operations (including multiple addresses and contacts) in the state were mailed a packet of information asking for their voluntary participation. Of the 491 potential operations, it was determined that 348 operations were currently in operation. Of those 348 operations, 48 (14% of the operations in the state) participated in a site visit and an in-depth interview, and a detailed site analysis of the water and nutrient management practices was performed on a production management unit (MU) basis. The authors define an MU as a group of plants that is managed similarly, particularly in regard to nutrient and irrigation application. Greenhouse operations reported, on average, 198, 122, and 196 kg/ha/year of nitrogen (N), phosphorus (P, as P2O5), and potassium (K, as K2O) fertilizer used, respectively, for 27 operations, representing 188 MUs. Twenty-seven outdoor container nursery operations had a total of 162 MUs, with an average of 964, 390, and 556 kg/ha/year of N, P2O5, and K2O fertilizer used, respectively. Field nursery (soil-based) operations were represented by 17 operations, producing 96 MUs, with an average of 67, 20, and 25 kg/ha/year of N, P2O5, and K2O fertilizer used, respectively. Irrigation volume per application was greatest in container nursery operations, followed by greenhouse and field nursery operations. Data were also analyzed by creating quartiles, which represent the median of the lowest 25%, the middle 50%, and highest 75% of values. It is likely that the greatest quartile application rates reported by growers could be substantially reduced with little to no effect on plant production time or quality. These data also provide baseline information to determine changes in fertilization practices over time. They were also used as inputs for water and nutrient management models developed as part of this study. These data may also be useful for informing nutrient application rates used in the Chesapeake Bay nutrient modeling process.