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Samantha Jay Forbes, Guiliana Mustiga, Alberto Romero, Tobin David Northfield, Smilja Lambert and Juan Carlos Motamayor

Artificial pollination management strategies are a potential solution to improving the livelihoods of smallholder cacao farmers by increasing crop productivity in situations when pollination services are limiting. However, field-based research trials evaluating the yield benefits of artificial pollination management strategies within intensified cacao systems are lacking. Thus, in an intensively managed cacao system, we evaluated the effects of artificial pollination condition (i.e., pollen genotype, pollination intensity, and pollination synchrony) on fruit development and yield in three high-yielding cacao clones. Artificial pollination, regardless of intensity, significantly increased fruit set and yield. Pollination synchrony had a significant effect on cherelle survivorship; older cherelles had greater survival rates across all developmental stages than younger cherelles. Yield differed between genotype crosses and varied according to the pollen donor used, highlighting the importance of understanding self- and cross-compatibility when selecting clones for cultivation. Pollination intensity had no significant effect on harvested yield, indicating that more rigorous research is needed to identify the pollination intensity required for optimized yield under artificial pollination conditions. We conclude that strategies to enhance flowering, pollination rates, and pollination synchrony while ensuring adequate tree nutrition may increase productivity in cacao. Future research evaluating numerous cacao clones across multiple years and locations may help us to understand the region-specific effects of intensive management strategies on the long-term sustainability of enhancing cacao tree productivity.

Open access

Zongyu Li, R. Karina Gallardo, Wendy Hoashi-Erhardt, Vicki A. McCracken, Chengyan Yue and Lisa Wasko DeVetter

Pacific Northwest North America (PNW) strawberry (Fragaria ×ananassa) growers are transitioning away from the processing to fresh-market sector in response to changes in local and regional markets. However, many of the regional cultivars bred for the PNW were not developed for the fresh market. There is a need to gain a better understanding of growers’ priority traits and their relative importance to enable breeders, researchers, and extension specialists to better serve this growing industry. The objective of this study was to provide such information on strawberry genetic traits of importance for the changing strawberry industry in the PNW with an emphasis on fresh-market production. Six surveys were administered to 32 growers representing ≈53%, 23%, and 15% of the total strawberry acreage in Oregon, Washington, and British Columbia, Canada, respectively. Growers ranked the relative importance of five plant and fruit traits, including fruit quality, disease resistance/tolerance, insect pest resistance/tolerance, plant stress tolerance, and other plant factors. Information about target markets, marketing channels, and general grower characteristics were also obtained. Whereas overall responses differed among the surveyed locations, fruit quality was considered the most important trait across all locations, with disease resistance/tolerance as the second most important. Specific fruit quality traits of importance were external appearance free of defects, skin color, size, sweetness, firmness, and flavor, whereas phytonutrients, seed color, and low drip loss after freezing and thawing were less important. Plant stress tolerance was identified as less important for strawberry growers in all locations. Results also showed many growers have already or are in the process of transitioning to the fresh market. Information obtained from this survey can be leveraged to target important breeding traits for fresh-market strawberry breeders within the PNW. Results also suggest priority areas of synergistic research and outreach activities to help growers achieve high fruit quality while managing diseases for fresh-market producers.

Open access

Neil O. Anderson

Historic ignorance of species’ native range, expansion due to unintentional involvement by vectors, and their quiet evolution has caused several invasive species to become “poster children,” such as purple loosestrife (Lythrum salicaria), reed canarygrass (Phalaris arundinacea), and others. Common misconceptions on how these became problematic have involved a variety of causes, including ignorance of species’ ability to intercross and create introgressive hybrids, lack of insects for control, wind pollination, and intercontinental distribution from their native range. Current research focuses on how misappropriating the historical contexts can reverse our misconceptions of native species being noninvasive and how this affects control by land managers. Purple loosestrife and reed canarygrass will be used as example species to demonstrate challenges that native vs. exotic, intra-, and interspecific differences confer to land managers. Issues such as a lack of phenotypic differences challenge land managers’ charge to control invasive individuals yet retain the noninvasives. This is fraught with challenges when native vs. exotic status is invoked or cultural values are entwined. To avoid a monumental impasse, particularly when native and exotic types are phenotypically indistinguishable, this dilemma could be solved via modern techniques using molecular biology.

Open access

Chengyan Yue, Jingjing Wang, Eric Watkins, Yiqun Xie, Shashi Shekhar, Stacy A. Bonos, Aaron Patton, Kevin Morris and Kristine Moncada

Identifying sources of turfgrass cultivar performance data can be difficult for many consumers. Currently, the best source for data of this type is the National Turfgrass Evaluation Program (NTEP). Unfortunately, these data are made public in a format that is not readily usable for most consumers. Ideally, turfgrass cultivar data would be available in an easily accessible database. We conducted an online survey to investigate user preferences for accessing publically available turfgrass performance data in the United States. We found users desire a turfgrass cultivar performance database that allows for the identification of cultivars best adapted and tolerant to environmental stresses. The information on turfgrass mixtures and blends is also important to most users. Users’ sociodemographic backgrounds, such as gender, education, occupation, and experience in the turf industry, affected their attitudes toward information provided in the turfgrass database. Turfgrass consumers need the new database to provide information on identifying turfgrass options that are resource efficient and endophyte resistant. Turfgrass breeders, researchers, and extension specialists use the turfgrass database to compare different turfgrasses cultivars to do further analysis. The results of this study provide important implications on how an updated turfgrass cultivar performance database and platform can fulfill the different needs of turfgrass researchers, extension personnel, breeders, and stakeholders.

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I-Chun Pan, Ya-Fen Lu, Pei-Jung Wen and Yen-Ming Chen

Commercially available novel cultivars of poinsettia, obtained through interspecific hybridization, were subject to colchicine-based mutagenesis to recover their fertility, enabling subsequent breeding. Mutagenic treatment was conducted at different concentrations of colchicine with either lanolin or cotton serving as the matrix. The results indicated that 1 day was the optimal duration of colchicine treatment and that suitable colchicine concentration varied by cultivar. Moreover, one-time treatment gave higher rates of both polyploidy and morphological mutant production than two-times treatment. Specifically, the poinsettia cultivars Dulce Rosa (5 mg·g−1 colchicine with lanolin; 10 mg·mL−1 colchicine with cotton) and Princettia-Hot Pink (15 mg·g−1 colchicine with lanolin; 10 mg·mL−1 colchicine with cotton) yielded relatively high polyploidy production efficiency and morphological mutation rate. Consequently, a total of three polyploidy mutants of ‘Dulce Rosa’ and 19 polyploidy mutants of ‘Princettia-Hot Pink’ were obtained. Both cultivars had mutants with recovered fertility, with pollen germination rate of up to 27.5%. Moreover, unexpected non-polyploidy mutants with various morphological trait variations were also obtained.

Open access

Yuan Li, Arend-Jan Both, Christian A. Wyenandt, Edward F. Durner and Joseph R. Heckman

Although not considered an essential nutrient, silicon (Si) can be beneficial to plants. Si accumulator species such as pumpkin (Cucurbita pepo var. pepo) can absorb Si from soil. Si uptake may reduce plant susceptibility to fungal diseases such as cucurbit powdery mildew (Podosphaera xanthii and Erysiphe cichoracearum). We previously reported that wollastonite, an Organic Materials Reviews Institute–approved natural mineral, can increase soil Si level, increase soil pH, provide pumpkin plants with Si, and increase their resistance to powdery mildew. In this study, we examined the optimum application rate of wollastonite for pumpkins grown in pots and exposed to cucurbit powdery mildew. We confirmed that wollastonite has liming capabilities similar to regular limestone. Regardless of the application rates, wollastonite and limestone showed similar effects on soil chemistry and plant mineral composition. Pumpkin plants grown with the lower doses of wollastonite amendments (3.13 and 6.25 tons/acre) had the greatest tissue Si concentrations and demonstrated the greatest disease resistance. We conclude that wollastonite is a useful material for organic cucurbit (Cucurbitaceae) growers who want to increase soil pH and improve plant resistance to powdery mildew at the same time. Applying wollastonite at rates beyond the amount required to achieve a desirable soil pH for pumpkin production did not further increase Si uptake, nor did it further suppress powdery mildew development.

Open access

Isaac T. Mertz, Nick E. Christians and Adam W. Thoms

Amino acids have been reported to improve turfgrass growth compared with mineral nutrition; however, amino acid catabolism in plants has not been well studied. A number of turfgrass fertilizers contain amino acids; however, some amino acids may be more effective additives in fertilizers than others. Three amino acids that could be effective nitrogen sources for plant growth are the branched-chain amino acids (BCAAs). The BCAA leucine (L), isoleucine (IL), and valine (V) could be effective additives because they are nonpolar and hydrophobic, which can promote plant uptake of these compounds. Although the effect of exogenously applied BCAA on plant growth is not well known, BCAAs have been reported to increase protein synthesis in humans, and that rate of increase is related to the intake ratio of L to IL and V. The objective of this study was to evaluate the use of L, IL, and V as a nitrogen sources on creeping bentgrass (Agrostis stolonifera) and to investigate the effect of BCAAs on plant growth when all three are applied as a combination. Using specially made rooting tubes, L, IL, and V were applied in a complete factorial and compared with equal urea nitrogen at four rates, as well as an untreated control. Where all three BCAAs were applied in combination, the application ratios of 2:1:1 and 4:1:1 (L:IL:V) were tested. At 63 days after seeding, there were no differences in root length, root weight, or shoot weight; however, BCAA 2:1:1 and 4:1:1 increased creeping bentgrass shoot density by 24% and 32%, respectively, compared with equal urea nitrogen. Where shoot density was increased, nitrogen application rate had no effect. On the basis of these results, BCAAs applied in a complete combination using ratios of 2:1:1 or 4:1:1 (3.03 lb/acre N) will provide a greater creeping bentgrass shoot density compared with equal urea nitrogen.

Open access

Kaitlyn M. Orde and Rebecca Grube Sideman

Day-neutral strawberry (Fragaria ×ananassa) cultivars show promise for extending the fruiting season and increasing production in the northeastern United States, but published research on cultivar yield in the region is lacking. Furthermore, few studies have investigated the effects of low tunnels on yield, fruit, and plant characteristics. We evaluated eight day-neutral cultivars (Albion, Aromas, Cabrillo, Monterey, Portola, San Andreas, Seascape, and Sweet Ann) on open beds and under low tunnels in two separate experiments conducted in 2017 and 2018. Cultivars began producing ripe fruit within 10 weeks of planting in both years, and continued producing fruit without interruption for 20 weeks (2017) and 18 weeks (2018). Annual total yield ranged from 234.9 to 497.8 g/plant and marketable yield ranged 126.4 to 389.1 g/plant, depending on cultivar and year. Cultivar significantly affected the percent marketable yield, late season yield, fruit size, soluble solids content (SSC), runner emergence, and plant size. Except for the cultivar Sweet Ann, low tunnels did not increase season-long marketable or total yield, but did increase the percent marketable yield for all cultivars in 2017, and most cultivars in 2018. Furthermore, marketable yield was significantly greater under low tunnels than open beds during 6 late-season weeks in 2018. Fruit SSC was greater under low tunnels in 2018, and low tunnels reduced runner emergence for certain cultivars. Season-long average air temperatures were higher under low tunnels, but the greatest temperature differences occurred when low tunnels were closed. We demonstrate that day-neutral cultivars can produce high annual yields in New England, but that cultivar selection is paramount.

Open access

Mary Hockenberry Meyer and Diane M. Narem

We tested prairie dropseed (Sporobolus heterolepis) using six different germination treatments and found the best results with cold (40 °F), dry storage followed by direct seeding into a commercial germination mix placed in a 75 °F glass-glazed greenhouse with intermittent mist (5 seconds of mist every 8 minutes), and 600-W high-pressure sodium lighting with a 16-hour daylength. We found commercial laboratory viability analysis from tetrazolium staining did not correspond to germination results. Cold (34 °F), moist (2.3 g seed moistened with 2.5 mL deionized water) treatment, also known as cold conditioning, produced significantly less germination and fewer transplantable seedlings, and is not recommended for prairie dropseed.