Wayne W. Hanna and Brian M. Schwartz
Zongyu Li, R. Karina Gallardo, Vicki A. McCracken, Chengyan Yue, Ksenija Gasic, Gregory Reighard, and James R. McFerson
U.S. peach (Prunus persica) growers are challenged by the need to protect their orchards from economically damaging diseases and deliver fruit with the quality expectations of the supply chain. This study focuses on the U.S. southeastern peach sector, including North Carolina, South Carolina, Alabama, Virginia, and Georgia. This region offers a useful case to analyze growers’ preferences for both fruit quality and disease resistance. We collected primary data from peach operations in 2016 and 2018. In both surveys, a discrete choice experiment was used to advance the understanding of how peach growers in the southeastern United States value fruit quality (i.e., fruit size and external color) vs. disease resistance [i.e., brown rot (Monilinia fructicola)]. The sample of growers surveyed in 2016 growers placed a greater importance on the fruit quality attribute that would imply higher returns, that is, fruit size (expressed as fruit diameter) compared with improvements in brown rot resistance and external fruit color. Meanwhile, the sample of growers surveyed in 2018 placed a higher importance to brown rot resistance and external fruit color compared with fruit size. Findings consistent for the 2 years are that growers are willing to pay for larger rather than smaller improvements in brown rot resistance, and that a large improvement in brown rot resistance is more important than external fruit color.
Fernando Montero de Espinosa Baselga, Jonathan R. Schultheis, Michael D. Boyette, Lina M. Quesada-Ocampo, Keith D. Starke, and David W. Monks
Internal necrosis (IN) is a physiological disorder that affects Covington, the most commonly grown sweetpotato (Ipomoea batatas) cultivar in North Carolina. Because IN affects the quality of sweetpotato storage roots, studies have been conducted since the first report of IN in 2006. Field studies (three in 2016 and two in 2017) were conducted to evaluate preharvest and postharvest treatments on the occurrence of IN in ‘Covington’ storage roots. Four preharvest treatments consisted of combinations of high chlorine or minimal chlorine potash fertilizer and mowing vs. not mowing before harvest. For postharvest treatments, 30 storage roots were obtained at harvest from each preharvest treatment plot and immediately cured in 75 and 85 °F rooms for a duration of 0.5, 1, 2, 3, and 5 weeks in 2016, and 0.5, 1, and 2 weeks in 2017. Shorter curing durations (0.5 and 1 week) coincided with industry recommendations while longer durations mimicked the challenges that some commercial facilities face when cooling down temperatures of rooms after curing is supposed to be concluded. Once curing temperature and curing duration treatments were completed, roots were placed in a 58 °F storage room at 85% relative humidity until cut. A control comparison was included in which harvested roots were placed in a 58 °F storage room (no curing) immediately after harvest. The storage roots from all temperature treatments were then cut 49 to 80 days after harvest, and incidence and severity of IN visually rated. Preharvest potash fertilizer treatments had minimal or no effect on occurrence of IN. However, mowing vines before harvest in several studies reduced IN incidence when roots were cured for more than 0.5 week at temperatures of at least 75 °F. Lower temperature (75 vs. 85 °F) and shorter curing duration (0.5 vs. 1, 2, 3, or 5 weeks) resulted in reduced IN occurrence in ‘Covington’ sweetpotato.
Roxana Myers, Brian Bushe, Cathy Mello, Joanne Lichty, Arnold Hara, Koon-Hui Wang, and Brent Sipes
Burrowing nematode (Radopholus similis) causes severe stunting and yield reduction in anthurium (Anthurium andraeanum) cut flower production. Two field trials were conducted at commercial grower farms to test the efficacy of fluopyram or fluopyram + trifloxystrobin for managing burrowing nematodes. Nematode population densities in roots and cinder media were evaluated during the trial in addition to cut flower yield and canopy cover. In the first trial, the nematode population in roots was reduced by 57% after two applications of fluopyram 3 months apart. As plant health improved, the increasing anthurium root weight supported higher nematode populations. After 14 months, fluopyram-treated plots had 43% more green canopy cover and a 53% increase in flower production compared with the untreated control plots. At a second location, population densities of burrowing nematode were reduced in roots after one application of fluopyram + trifloxystrobin and remained low with quarterly applications. Nematode populations were initially reduced in fluopyram-treated plots followed by a resurgence as demonstrated in the other trial. Ten months after the initial treatment, flower yield was greater in fluopyram + trifloxystrobin-treated plots with more large and extra-large flowers produced. Canopy cover was 45% and 22% greater with fluopyram + trifloxystrobin and fluopyram applications, respectively. Fluopyram shows potential for management of burrowing nematodes in anthurium by improving plant vigor and cut flower production.
Hyungmin Rho, Paul Colaizzi, James Gray, Li Paetzold, Qingwu Xue, Bhimanagouda Patil, and Charles Rush
The Texas High Plains has a semi-arid, hot, windy climate that features high evapotranspiration (ET) demands for crop production. Irrigation is essential for vegetable production in the region, but it is constrained by depleting groundwater from the Ogallala Aquifer. High-tunnel (HT) production systems may reduce irrigation water demand and protect crops from severe weather events (e.g., hail, high wind, freezing) common to the region. The objective of this study was to compare yields, fruit quality, crop water use, and crop water use efficiency (WUE) of jalapeno pepper (Capsicum annuum L.) and tomatoes (Solanum lycopersicum L.) in HT and open field (OF) production systems. We hypothesized that the protection from dry and high winds by HT would improve yields and quality of fruits and reduce water use of peppers and tomatoes. During the 2018 and 2019 growing seasons, peppers and tomatoes were transplanted on two HT plots and two identical OF plots. Plastic mulch was used in combination with a surface drip irrigation system. Micrometeorological variables (incoming solar irradiance, air temperature, relative humidity, and wind speed) and soil physical variables (soil temperature and volumetric soil water) were measured. Air temperatures were significantly higher during the daytime, and wind speed and light intensity were significantly lower in HT compared with OF. Despite the lower light intensity, yields were greater in HT compared with OF. The fruits grown in HT did not show significant differences in chemical quality attributes, such as ascorbic acid and lycopene contents, compared with those grown in OF. Because of protection from dry, high winds, plants in HT required less total water over the growing seasons compared with OF, resulting in increased WUE. The 2018 and 2019 data showed that HT production is advantageous as compared to conventional OF production in terms of increased WUE and severe weather risk mitigation for high-value vegetable production in the Texas High Plains.
Yun Kong, Katherine Schiestel, David Llewellyn, and Youbin Zheng
Intercropping can increase land use efficiency in high tunnel crop production, but it may also lead to decreases in yield and quality of main crops due to the potential competition for resources. This study evaluated the agronomic viability of intercropping snow pea (Pisum sativum L., ‘Ho Lan Dou’) with cherry tomato (Solanum lycopersicum L. var. cerasiforme ‘Sarina hybrid’) without additional inputs of water and fertilizers on peas in an organic high tunnel production system under Southern Ontario climate conditions in Guelph, Ontario, Canada (lat. 43.5 °N, long. 80.2 °W) during 2015 and 2016. In each 80-cm-wide bed, the tomato crops were planted alternately in double rows spaced 30 cm apart, with in-row spacing of 110 cm, which resulted in a planting density of ≈24,000 plants/ha. The snow pea seeds were sown between the tomato plants (i.e., within the same beds as tomatoes) in holes (two seeds per hole), with four rows in each bed and in-row holes spaced 10 cm and at least 25 cm away from the tomato plants, which resulted in a seeding rate of ≈650, 000 seeds/ha. The same amount of water or fertilizer was applied to the intercropping and nonintercropping plots based on the needs of the cherry tomato plants. Plant growth, fruit yield, and quality were compared between tomato plants with and without intercropping. Intercropping with snow peas did not affect total marketable fruit yield, unmarketable fruit percentage, fruit quality traits (e.g., individual fruit weight, soluble solids content, dry matter content, and postharvest water loss), or early-stage plant growth of the cherry tomato. Therefore, it is at least an agronomical possibility to intercrop snow peas with cherry tomatoes on the same beds without additional inputs of water and fertilizer on snow peas in an organic high tunnel system. The additional yield of pea shoots or pods in the intercropping treatment also increased economic gross returns in the high tunnels, although the economic net return might vary with the costs of seeds and labor involved in snow pea growing.
Hardeep Singh, Megha R. Poudel, Bruce Dunn, Charles Fontanier, and Gopal Kakani
Increase in ambient carbon dioxide (CO2) concentration is beneficial for plant growth due to increased photosynthesis and water use efficiency. A greenhouse study was conducted to investigate how supplemented CO2 influences optimal irrigation and fertilization management for production of two ornamental plants. Two identical greenhouses were used, with one having CO2 supplementation and the other serving as the control with ambient CO2 concentration. Tensiometer-based irrigation treatments were applied at soil tensions of –5, –10, and –15 kPa with 0-, 3-, 6-, or 9-g controlled-release fertilizer rates applied in factorial with irrigation treatments. Plugs of geranium ‘Pinto Premium Rose Bicolor’ and fountain grass were grown under experimental conditions for 12 and 16 weeks, respectively. The results showed that CO2 supplementation increased the dry weight of geranium ‘Pinto Premium Rose Bicolor’ and fountain grass by 35% and 39%, respectively. Under the two driest irrigation regimes (–10 and –15 kPa), photosynthesis of geranium ‘Pinto Premium Rose Bicolor’ increased with CO2 supplementation compared with the ambient condition. Similarly, for fountain grass, the moderately watered (–10 kPa) treatment had a greater rate of photosynthesis with greater fertilizer rates of 6 or 9 g. CO2 supplementation resulted in increased water use efficiency of both species, whereas rate of transpiration was lower only in fountain grass. Among different fertilizer rates, 6- or 9-g fertilizer rates had greater values for dry weight, number of flowers, and stomatal conductance in both species. Therefore, it can be concluded that CO2 supplementation can help in efficient use of water for greenhouse production of ornamental plants.
Anna Underhill, Cory Hirsch, and Matthew Clark
Grape (Vitis vinifera) cluster compactness is an important trait due to its effect on disease susceptibility, but visual evaluation of compactness relies on human judgement and an ordinal scale that is not appropriate for all populations. We developed an image analysis pipeline and used it to quantify cluster compactness traits in a segregating hybrid wine grape (Vitis sp.) population for 2 years. Images were collected from grape clusters immediately after harvest, segmented by color, and analyzed using a custom script. Both automated and conventional phenotyping methods were used, and comparisons were made between each method. A partial least squares (PLS) model was constructed to evaluate the prediction of physical cluster compactness using image-derived measurements. Quantitative trait loci (QTL) on chromosomes 4, 9, 12, 16, and 17 were associated with both image-derived and conventionally phenotyped traits within years, which demonstrated the ability of image-derived traits to identify loci related to cluster morphology and cluster compactness. QTL for 20-berry weight were observed between years on chromosomes 11 and 17. Additionally, the automated method of cluster length measurement was highly accurate, with a deviation of less than 10 mm (r = 0.95) compared with measurements obtained with a hand caliper. A remaining challenge is the utilization of color-based image segmentation in a population that segregates for fruit color, which leads to difficulty in differentiating the stem from the fruit when the two are similarly colored in non-noir fruit. Overall, this research demonstrates the validity of image-based phenotyping for quantifying cluster compactness and for identifying QTL for the advancement of grape breeding efforts.
Jose Martínez-Calvo and María L. Badenes
Mun Wye Chng and Kimberly A. Moore
Bougainvillea (Bougainvillea sp.) plant inflorescence number will vary in response to multiple cues such as changes in temperature, water, light intensity, pruning, and photoperiod. Previous research reports that the application of plant growth regulators (PGRs) to bougainvillea grown under varying photoperiods improved inflorescence number, probably as a result of changes in gibberellic acid (GA) levels. There are many bioactive plant GAs, but we chose to investigate differences in gibberellic acid 3 (GA3) levels and inflorescence number in response to the application of ethephon (2-cholorethylphosponic acid) or abscisic acid (ABA) to ‘Afterglow’ bougainvillea (Bougainvillea ×buttiana) grown under 14-hour photoperiod [long-day (LD)] conditions. Plants were 5 inches tall with seven visible lateral nodes and were grown in a greenhouse in 4-inch pots filled with 5-mm coarse aquarium zeolite. Ethephon was applied as a foliar spray at 0.05, 0.07, 0.10, 0.15, or 0.20 mg/plant. ABA was applied as a soil drench at 1, 1.5, 3, 6, 8, or 10 mg/plant. Endogenous levels of GA3 were measured 1 and 48 days after treatment to calculate the change in GA3 (∆GA3). A short day (SD) control of 8 hours was included to measure differences in inflorescence number and ∆GA3 between photoperiods. ‘Afterglow’ plants grown under SD conditions had the greatest decrease in ∆GA3 (–1.09 µg·g–1) over 48 days and the most inflorescences (10.6) compared with LD control plants with a decrease in ∆GA3 of –0.09 µg·g–1 and fewer inflorescences (1.0). Plants grown under LD conditions and treated with 0.05 mg/plant ethephon had inflorescence numbers (9.6) and levels of ∆GA3 (–0.74 µg·g–1) similar to the SD control. As ethephon rate increased to more than 0.05 mg/plant, inflorescence number on LD plants decreased and ∆GA3 increased. Exogenous ABA rates of 1 mg/plant produced inflorescence numbers (1.4) and ∆GA3 (–0.10 µg·g–1) similar to the LD control. As the rate increased, ∆GA3 increased and inflorescence number decreased. Plants treated with ABA rates of 3 mg/plant and more were defoliated and had no inflorescences.