ALBERT

Description: Balsam poplar (Populus balsamifera L.) is a transcontinental tree species in North America, making it an ideal species to study intra-specific hybrid vigour as a tool for increasing genetic gain in growth. We tested the hypothesis that intra-specific breeding of disparate populations of balsam poplar would lead to the expression of hybrid vigour and we determined the role of endogenous hormones linked to ecophysiological and growth performance. In September 2009, three field trials were established in Canada (two in Alberta (AB), i.e., Fields AB1 and AB2, and one in Quebec (QC), i.e., Field QC1) in conjunction with Alberta-Pacific Forest Industries Inc. and the Ministry of Forests, Wildlife and Parks, Quebec. Five male parents from each province as well as five female parents from QC and four female parents from AB were used for breeding intra-regional and inter-regional crosses. Based on a significant difference at year six for height and diameter, from the AB1 and AB2 field trials, the AB × QC cross-type was selected for further study. Cuttings from the AB × QC cross-type were grown in a randomized complete block design under near-optimal greenhouse conditions. Families were identified as slow- or fast-growing, and the relationship between hormone levels and growth performance of the genotypes within the families were examined. In late June, after 34 days of growth, internode tissue samples collected from each progeny were analyzed for gibberellic acids, indole-3-acetic acid, and abscisic acid content. Stem volume of two-month-old rooted cuttings, grown under optimal greenhouse conditions, was positively and significantly correlated with the photosynthetic rate, greenhouse growth, and stem volume of 8-year-old field-grown trees (Fields AB1 values: r = 0.629 and p = 0.012; AB2 values: r = 0.619 and p = 0.014, and QC1 values: r = 0.588 and p = 0.021, respectively). We determined that disparate and native populations of balsam poplar can be bred to produce superior progeny with enhanced stem growth traits.

Description: Deployment of well-adapted, water use efficient, and productive genotypes may be essential for the sustainability of both forests and wood supply for the forest industry, as climate change is increasing water stress around the world. This study aimed to characterize key traits among new genotypes of hybrid poplars (Populus spp.) in water use efficiency (WUE) and evaluate adaptive capacity to guide the selection of appropriate clones/hybrid types for commercial deployment in habitats with an increasing water deficit in northern, continental climates. Forty-five new hybrid poplar genotypes were compared at the age of 10, including two control clones, Walker and Okanese, growing in a common garden genetics trial in northern Alberta. We studied the relationships between their productivity and WUE, photosynthetic assimilation, transpiration, stomatal conductance, stomatal density and length, and leaf size and weight. In addition, the genetic variance and heritabilities of physiological and morphological characteristics related to WUE were calculated. Results of this study revealed that most of the clones showed an adaptive capacity to acclimatize (small and dense stomata) to the region of deployment. Morphological traits were characterized by higher heritabilities than physiological traits. Hybrids between Populus balsamifera and Populus maximowiczii species showed a slightly greater adaptive potential to the area of our study than the other tested cross types. Walker, a clone widely planted across the Canadian prairies, showed inferior WUE and productivity in comparison to the new genotypes tested. Selection and tree breeding for adaptation to climate change in the region of our investigation identified highly productive genotypes with dense, small stomata and a larger leaf area to dry mass ratio. As these traits are heritable, selection of clones with these traits will ensure a faster reaction of stomata when faced with a water deficit. The low genetic effect, heritability estimates, and high residual effect for physiological traits, impose a severe limitation on the use of gas exchange measurements under field conditions in tree improvement programs selecting for drought resistance.

Description: Managers of ornamental nurseries are increasingly reusing runoff water as an irrigation source, but residual pesticides in recycled water may result in plant phytotoxicity on crop plants. Our study focused on understanding the responses of container-grown landscape plants to residual pesticides in irrigation water. Hydrangea paniculata ‘Limelight’, Cornus obliqua ‘Powell garden’, and Hosta ‘Gold standard’ were exposed to various concentrations of isoxaben, chlorpyrifos, and oxyfluorfen (0, 0.15, 0.35, 0.7, and 1.4 mg/L of isoxaben; 0, 0.05, 0.1, 0.2, and 0.4 mg/L of chlorpyrifos; and 0, 0.005, 0.01, 0.015, and 0.02 mg/L of oxyfluorfen) applied as overhead irrigation. After three months of application, we assessed the dry weight biomass, growth, and parameters related to photosynthetic physiology (SPAD chlorophyll index, light-adapted chlorophyll fluorescence, and photosynthesis carbon dioxide response (A/Ci) curves. We also sampled plant leaf, stem, and root tissues for residual pesticides. The effects of the pesticides were pesticide-specific and taxa-specific. Exposure to oxyfluorfen resulted in visible injury in all three taxa and reduced total biomass, chlorophyll index, and photosynthesis in Hydrangea and Hosta. All three taxa absorbed and retained pesticides in leaf and stem tissues. Growers should follow best management practices to reduce exposure from irrigation with runoff, particularly for herbicides with post-emergent activity.

Description: Nursery, floriculture, and propagation production accounted for 79% ($13.3 Billion) of 2017 ornamental specialty crop production in the United States. Access to high quality water sources is increasingly limited for irrigating these economically significant crops. Given the production, environmental, and economic issues associated with the use of water—including recycled, reclaimed, surface, and ground water—it is critical to develop sustainable runoff, containment, and remediation technologies, and to identify alternative sources of water. To better understand current practices and future water-related needs as perceived by grower stakeholders, an online survey was distributed nationally and five in-depth round table discussion sessions were conducted at the Mid-Atlantic Nursery Trade Show, Gulf States Horticultural Expo, California Grown Show, AmericanHort’s Cultivate, and the Farwest Show with a total of 36 individual industry participants. A team of research and extension specialists facilitated by a Specialty Crops Research Initiative Planning Grant (NIFA Project # 2011-51181-30633) analyzed and concisely summarized the results from the survey and the round table discussions. Research priorities related to water management identified by stakeholders revolved around six themes: (1) recycled water infrastructure and management; (2) contaminants; (3) plant health and water quality; (4) water treatment technologies; (5) competing and complementary water uses; (6) societal perception of agricultural water use.