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Open access

Mark K. Ehlenfeldt, James J. Polashock, Lisa J. Rowland, Elizabeth Ogden, and James L. Luteyn

Vaccinium meridionale (section Pyxothamnus), a tetraploid species native to higher-altitude locations in Jamaica, Colombia, and Venezuela, is of interest to Vaccinium breeders for its profuse, concentrated flowering, vigor, and monopodial plant structure, all of which may be useful in breeding for mechanical harvest in blueberry. In this study, tetraploid V. meridionale was successfully hybridized as both female and male with 2x Vaccinium vitis-idaea (section Vitis-idaea, lingonberry). The resultant F1 hybrids with lingonberry were both 3x and 4x, respectively. These hybrids were intermediate in morphology and notably vigorous. Most appear to be evergreen, with small, red-colored fruit. The 4x F1 hybrids displayed good fertility as females in backcrosses to both lingonberry and V. meridionale. Pollen production and quality were evaluated as an indicator of male fertility. Most clones had good pollen shed and high frequencies of well-formed tetrads. The overall fertility suggests that these hybrids, despite being derived from intersectional crosses, might be conventionally used for breeding without substantial difficulty.

Open access

Jason D. Lattier and Ryan N. Contreras

Althea (Hibiscus syriacus) is a popular shrub known for its vibrant summer blooms and winterhardiness; however, althea produces capsules with numerous seeds that germinate and cause a nuisance in production and the home landscape. Breeding for sterile forms has long been a goal of Hibiscus breeders, yet many popular “sterile” cultivars have been reported as weedy. The purpose of this study was to evaluate female and male fertility of tetraploid and hexaploid cultivars, and to evaluate the female fertility of pentaploid progeny resulting from 4x × 6x and 6x × 4x crosses. More than 600 self-pollinations were performed on 21 cultivars, yet only 24% of self-pollinations resulted in filled capsules, for an overall rate of four seeds per pollination. Significant differences were observed among taxa for seeds per capsule and seeds per pollination. Highest capsule set was observed on self-pollinated White Chiffon® and Pink Chiffon®. Anecdotally, we observed reduced vigor in the S1 generation of most taxa. However, ‘Woodbridge’ produced vigorous seedlings through the S2 generation. More than 2000 cross-pollinations were also performed, resulting in more than 15,000 seeds. To evaluate female fertility, 28 taxa were pollinated with a variety of male parents. Fertility was measured as seeds per capsule and seeds per pollination. Significant differences were found among taxa within and among flower forms (single, semidouble, and double) for seeds per capsule and seeds per pollination. Double-flowered forms had reduced female fertility. Taxa previously reported to be sterile were found to be fertile, including ‘Aphrodite’, ‘Diana’, ‘Helene’, and ‘Minerva’. Two hexaploids, ‘Pink Giant’ and Raspberry Smoothie™, had reduced female fertility compared with tetraploids. Male fertility was estimated for 20 cultivars by pollinating between one and 23 cultivars. For male fertility, significant differences were found among taxa for seeds per capsule and seeds per pollination; however, no significant differences in male fertility were observed among flower forms. Four taxa had relatively high fertility with more than 10 seeds per capsule and seeds per pollination, including Blue Satin®, Lil’ Kim™, Bali™, and Tahiti™. In addition to the significant differences among female and male fertility of each taxon, capsule set varied widely among individual cross combinations. Significant differences of female fertility were found in pairwise comparisons between almost all pentaploid taxa and the mean of tetraploid control cultivars. No difference in percent seed germination was observed between 4x × 6x and 6x × 4x crosses (45% and 45%, respectively) but both were significantly lower than seeds from open-pollinated tetraploids (89%). The reduced fertility of pentaploids will likely lead to new reduced fertility or sterile cultivars for the nursery industry, especially if combined with double flowers.

Open access

Mark H. Brand and Shelley N. Durocher

Berberis thunbergii L. (Japanese barberry) holds significant market share in the commercial ornamental horticulture industry. Japanese barberry is grown by production nurseries and used in landscaping across the northern half of the United States. In 2009, the barberry crop was worth nearly $30.5 million in annual sales in the United States, making it one of the top two ornamental shrubs, roses excluded. [U.S. Department of Agriculture (USDA) 2009]. Dirr (2009) lists close to 70 cultivars of B. thunbergii or B. thunbergii hybrids, and new cultivars continue to be introduced at a rapid rate.

Open access

Fengyi Li, Ling Wang, Zhiyang Liu, Wangbin Ye, Lei Yan, Juan Yang, Xi Chen, Wanjie Men, and Lijuan Fan

Genus Hemerocallis (daylilies) is composed of 14 species with yellow, orange, and red flower colors (Cui et al., 2019). Daylilies are among the most popular ornamental herbaceous perennials (Griesbach, 2004) and are widely cultivated all over the world because of their attractive appearance, excellent drought tolerance, pest and disease resistance, and survival in a wide range of soils under full sun or slight shade conditions (Blythe et al., 2015; Li et al., 2021; Podwyszyńska et al., 2015). More than 90,000 Hemerocallis cultivars have been registered in

Open access

Timothy Coolong, Kate Cassity-Duffey, and Andre Luiz Biscaia Ribeiro da Silva

Georgia is a leading fresh market cabbage (Brassica oleracea var. capitata) producer. Current recommendations for bare-ground cabbage grown in the Coastal Plain of Georgia indicate 175 to 225 lb/acre nitrogen (N). Approximately one-third of N fertilizer is recommended at planting, with two or three additional side-dress applications during the season. Growers have begun banding liquid fertilizer between four and six times during the season to reduce N leaching and enhance productivity. To determine the validity of current recommendations as well as the efficacy of applying periodic liquid fertilizer throughout the growing season, field experiments were conducted in Tifton, GA in Fall 2016 and 2017 with the cabbage cultivar Cheers. Fertilizer N rates were 175, 200, 225, and 250 lb/acre N applied using equivalent preplant fertilizer (50 lb/acre N) with two posttransplant applications of a granular fertilizer (27–0P–0K–5Ca) or six applications of a liquid fertilizer (9N–0P–0K–11Ca). A factorial, randomized, complete block design was used. There were no interactions among fertilizer program, N rate, or year for cabbage yield or nutrient concentrations. Total yield was unaffected by the N rate. However, plants fertilized with the lowest N rate (175 lb/acre N) had the lowest yields from the first two harvests compared with the other N rates. Nutrient concentrations were affected by year, with 2017 having greater concentrations of most macronutrients compared with 2016. In conclusion, the application of 175 lb/acre N led to a potential delay in harvest, but all other N rates were equal. The application method did not impact yield or earliness, suggesting that current recommendations for fertilizer applications after planting cabbage in Georgia are adequate.

Open access

Chengyan Yue, Manlin Cui, Xiangwen Kong, Eric Watkins, and Mike Barnes

Outdoor water use, especially for lawn and landscaping irrigation, accounts for a substantial proportion of residential water use and often peaks during summer months. Understanding how to reduce outdoor water use can play a critical role in balancing the increasing demand for and subsequent protection of water resources. This study aims to find out if information-based strategies can be effective in reducing homeowners’ water use as well as identifying the key determinants that can enhance water conservation campaigns. Using online survey data from 2077 randomly selected urban homeowners with home lawns in a relatively water-rich state, we found that social norm-based information is generally more effective to promote household water conservation behavior than education information. Moreover, the results showed that the households’ water-saving actions, lawn watering knowledge, awareness for local water scarcity, attitudes toward water conservation, socio-demographics, and landscape characteristics all play a role in determining household water conservation intention.

Open access

Lyn A. Gettys, Kyle L. Thayer, and Joseph W. Sigmon

Herbicides that are labeled for aquatic use are often the foundation of aquatic vegetation management programs in the United States because many of these products, which are registered by the U.S. Environmental Protection Agency, are effective, selective, and relatively inexpensive. Resource managers are interested in reducing the use of synthetic herbicides and are considering alternative methods for aquatic weed control. We evaluated the effects of acetic acid and d-limonene on growth of the invasive small floating species feathered mosquitofern (Azolla pinnata) and common salvinia (Salvinia minima), as well as on the native emergent wetland plants cattail (Typha latifolia) and gulf coast spikerush (Eleocharis cellulosa). Acetic acid and d-limonene (alone and in combination) were applied once as foliar treatments to healthy plants, which were grown for 8 weeks after treatment to allow for development of phytotoxicity symptoms. All experiments also included diquat dibromide at three concentrations as “industry-standard” treatments for comparison. A 0.22% concentration of diquat dibromide eliminated all vegetation of all species. Most single-product treatments provided good control of invasive feathered mosquitofern with acceptable levels of damage to native gulf coast spikerush, but only 15% and 20% d-limonene treatments were effective on invasive common salvinia and selective for native cattail. Some combinations of acetic acid and d-limonene provided acceptable control of both floating weeds and selectivity for gulf coast spikerush, but all mixes caused unacceptable levels of damage to cattail. Treating these small floating weeds with acetic acid and d-limonene instead of diquat dibromide would increase material costs by 15- to 27-fold. Although these natural products may be useful in some areas where synthetic herbicides are discouraged, they are unlikely to be affordable options for most resource managers.

Open access

Srijana Shrestha and Carol Miles

Sweetpotato (Ipomoea batatas) production in the northern United States is limited due to the perceived barriers of a short growing season and relatively cool summer temperatures, yet recent studies have shown yield in northern regions can be greater than the national average when sweetpotatoes are grown with plastic mulch. A study was conducted in northwest Washington to evaluate the productivity of ‘Covington’ sweetpotato with polyethylene (PE) and soil-biodegradable (BDM) mulches and different in-row spacings (20, 30, and 38 cm) in 2019, and to test accessions resistant to wireworm (Agriotes sp. and Limonius sp.) in 2020. In 2019, slips were shipped from North Carolina, and after 4 days in transit, 60% to 70% died after transplanting in the field. By the end of the season, BDM deterioration reached 11% compared with 0.4% for PE mulch, but there were no differences due to mulch in plant establishment, growth, yield, or the proportion of storage roots damaged by wireworm. Total storage root yield was 22 t⋅ha−1 with PE mulch and 15 t⋅ha−1 with BDM. Percent canopy cover was greatest at 20-cm spacing later in the growing season, likely due to intermingling of vines from adjacent plants, whereas high percent canopy cover at 38-cm spacing was likely due to increased production of secondary vines per plant. Total yield was greatest with 20-cm plant spacing (20.4 t⋅ha−1), intermediate with 30-cm spacing (18.0 t⋅ha−1), and lowest with 38-cm spacing (17.0 t⋅ha−1). In contrast, the greatest number of storage roots per plant was produced with 38-cm plant spacing (3.4). There were more jumbo sweetpotatoes produced with PE mulch (3.4 t⋅ha−1) and with 30-cm spacing (3 t⋅ha−1), and the weight of U.S. No. 2 grade sweetpotatoes was greatest at 20-cm spacing (10.2 t⋅ha−1). Soil temperature was increased by 3 °C under the PE mulch and 2 °C under the BDM compared with bare ground. However, 98% of storage roots were observed to be severely damaged by wireworm in 2019, with more than 10 to 20 holes per storage root. For wireworm-resistant accessions in 2020, 16% of the storage roots were damaged by wireworm, with 1.7 to 4.0 holes per storage root. Total yield of accessions PI 666141 and 04-791 (45.5 t⋅ha−1 on average) was greater than the national average (24.7 t⋅ha−1). Overall, sweetpotatoes appear to be suitable for production in northwest Washington, but low yield in 2019 highlights the importance of healthy slips for successful production. Future research should evaluate cultivars with maximum adaptation to the region, techniques to reduce wireworm damage including genetic resistance, and the economics of producing sweetpotatoes in northern regions.