Marker-assisted selection (MAS) use in breeding programs allows for examination of seedlings at an early stage before accumulation of high field costs. However, introducing MAS into a breeding program implies additional costs and uncertainties about effective incorporation. Previous simulations in apple (Malus ×domestica) have shown cost-effective applications of MAS. To further evaluate MAS cost-effectiveness in perennial crops, we conducted a cost-effectiveness analysis examining MAS in an upper midwestern U.S. peach (Prunus persica) breeding program. Breeding program procedures and associated costs were collected and used as input into spreadsheet-based simulations of the breeding program. Simulations compared a conventional breeding program to MAS with varying cull rates of low, medium, and high at multiple stages in the breeding cycle. Cost-effective MAS implementation was identified at the end of seedling trials with a break-even cull rate of 4%. These results inform breeders of cost-effectiveness of MAS use in a peach breeding program.
Seth D. Wannemuehler, Chengyan Yue, William W. Shane, R. Karina Gallardo and Vicki McCracken
Guoqiang Wang, Ping Qu, Hongying Huang, Guofeng Wu and Haijun Yan
To produce a firm and cohesive root plug to promote automated transplanting of nursery-grown seedlings, hydrolyzed soy protein-modified urea–formaldehyde (H-UF) resins were used to bind renewable substrate [mixture of coconut (Cocos nucifera) coir dust, coconut fiber, organic manure, perlite, vermiculite]. The resulting substrate block showed high density and nutrient concentrations in the peripheral portion and relatively low density and nutrient levels in the center. The porosity of the H-UF/substrate block was slightly lower than that of standard substrate. The electrical conductivity and pH were beneficial for germination and early seedling development. The modified resins in the substrate block existed in the form of spheres that adhered to each other and formed a porous structure from nano- to micrometer scale. In particular, the H-UF/substrate block increased the seedling height, stem diameter, root length, and leaf area of ‘Sujiao No. 5’ pepper (Capsicum annum) seedlings by 56.07%, 43.33%, 1.33%, and 89.63%, respectively, compared with those of seedlings grown in substrate without H-UF resin. The contents of nitrogen, phosphorus, and potassium in the shoot and root of pepper seedlings grown in H-UF/substrate blocks were enhanced by 39% to 69% compared with those of seedlings grown in standard substrate. The compressive strength of the H-UF/substrate block was 3.6-fold higher than that of substrate when 50% resin was added to the substrate. The results indicated that a combination of the substrate with the modified resin was suitable as a growth substrate for nursery production of pepper seedling plugs.
Kevin T. Walsh and Tina M. Waliczek
The free-floating algae known as sargassum (Sargassum fluitans and Sargassum natans) drifts onto coastlines throughout the Atlantic Ocean during spring and summer months. Beach communities seek to maintain tourist appeal and, therefore, remove or relocate the sargassum drifts once it collects on shore. Maintenance efforts have attempted to incorporate the sargassum into dunes and beach sand. However, not all communities have the resources to manage the biomass and must dispose of it in a landfill. The utility of the seaweed biomass as a fertilizer for plant growth has been renowned for centuries. The purpose of this project was to evaluate the appropriate proportion of sargassum for other compost ingredients used in a large-scale composting system to create a quality product for utilization in horticultural and/or agricultural products. This study used ≈32 yard3 of sargassum as part of 96 yard3 of compost material that also included food waste, fish waste, and wood chips. Four protocols were prepared and included either 25% or 41.5% sargassum and various proportions of food or fish waste and wood chips, which are ingredients that would be readily available in coastline communities, to determine the ideal ratios of materials to create a quality compost. Piles were turned regularly and monitored for pH, moisture, and temperatures according to compost industry standards and approximately every 5 to 7 days. Piles cured for 4 to 8 weeks and the entire composting process lasted 5 months. Samples of compost were collected and tested through the Agricultural Analytical Services Laboratory’s U.S. Composting Council’s Seal of Testing Approval Program at Pennsylvania State University. All final compost products and protocols had reasonable quality similar to those required by current compost standards. However, the protocol incorporating equal parts sargassum (41.5%) and wood chips (41.5%), fish waste (4%), and food waste (13%) had the best results in terms of organic matter content and overall nutrient levels. Therefore, this study determined that waste management industries can use sargassum as a feedstock through a large-scale composting system to create a desirable compost product that could be used in the horticulture industries. Sargassum could also be composted and then returned to the shoreline, where it would help build soils and vegetation.
Julie Campbell, Alicia Rihn and Hayk Khachatryan
Home lawn fertilizer use throughout the United States is coming under increased scrutiny due to potential negative environmental impacts. A better understanding of how consumer perceptions and socio-demographics impact their choices of types of lawn fertilizers can aid industry stakeholders when marketing products. This research uses a nationwide survey to evaluate factors that impact respondents’ choice of lawn fertilizer brands. Respondents with home lawns selected the lawn fertilizer brands they purchased the most frequently and rated the importance of various fertilizer attributes (e.g., nitrogen–phosphorus–potassium ratio, brand, price, etc.) when selecting lawn fertilizers. Given many lawn fertilizer brands share commonalities, respondents’ answers were grouped into five categories: most popular brand, primarily turf brands, sustainable/organic brands, other brands, and “I don’t remember the brand.” The most popular brand of fertilizer was chosen by 69% of respondents, with the primarily turf brands and other fertilizers being chosen by 25% and 23% of respondents, respectively. This study finds that brand selection is impacted by important fertilizer features, frequented retail outlets, geographical region of residence, and demographic variables. For example, brand importance and purchasing from mass merchandisers or wholesale clubs increased respondents’ selection likelihood of the most popular brand by 6.9% and 20.5% points, respectively. Marketing implications are discussed.
Chad E. Finn, Bernadine C. Strik, Brian M. Yorgey, Mary E. Peterson, Patrick A. Jones, Gil Buller, Jungmin Lee, Nahla V. Bassil and Robert R. Martin
Roxana Myers, Andrea Kawabata, Alyssa Cho and Stuart T. Nakamoto
Kona coffee root-knot nematodes (Meloidogyne konaensis) cause severe declines in ‘Kona Typica’ arabica coffee (Coffea arabica) trees in Hawaii. Defoliation and destruction of the root system result in significant yield losses and can kill the host. Grafting with other coffee (Coffea) species that exhibit tolerance to kona coffee root-knot nematodes is a viable solution for mitigating damage in the field. An infested field was established in 2006 with ‘Kona Typica’ scions grafted on seven accessions of promising rootstock and nongrafted ‘Kona Typica’ as the control. Four grafted trees of each accession were planted per plot with four repetitions. Yield data were assessed for the 2016–17, 2017–18, and 2018–19 seasons. Three liberica coffee (Coffea liberica) accessions [‘Arnoldiana’ (‘Arnoldiana’ 1 and ‘Arnoldiana’ 2), ‘Dewevrei’, and ‘Fukunaga’ 1], demonstrated higher yields of coffee cherry compared with nongrafted ‘Kona Typica’ in the 2016–17 season. In the 2017–18 and 2018–19 seasons, five accessions of liberica and ‘Nemaya’ robusta coffee (Coffea canephora) exhibited higher cherry yields than ‘Kona Typica’. Plant vigor was greater in trees grafted on ‘Arnoldiana’ and ‘Fukunaga’ compared with other accessions and nongrafted ‘Kona Typica’, with taller trees, higher vertical branches, thicker trunk circumferences, and overall better health. After 13 years in the field, nongrafted ‘Kona Typica’ showed the highest mortality, with 81% of trees lost. Liberica rootstocks performed consistently well in the presence of kona coffee root-knot nematodes, with the healthiest trees, highest yields, and least mortality of the coffee species evaluated.
Kellie J. Walters, Bridget K. Behe, Christopher J. Currey and Roberto G. Lopez
Controlled environment (CE) food crop production has existed in the United States for many years, but recent improvements in technology and increasing production warranted a closer examination of the industry. Therefore, our objectives were to characterize historical trends in CE production, understand the current state of the U.S. hydroponics industry, and use historical and current trends to inform future perspectives. In the 1800s, CE food production emerged and increased in popularity until 1929. After 1929, when adjusted for inflation (AFI), CE food production stagnated and decreased until 1988. From 1988 to 2014, the wholesale value of CE food production increased from $64.2 million to $796.7 million AFI. With the recent increase in demand for locally grown food spurring an increase in CE production, both growers and researchers have been interested in using hydroponic CE technologies to improve production and quality. Therefore, we surveyed U.S. hydroponic food crop producers to identify current hydroponic production technology adoption and potential areas for research needs. Producers cited a wide range of technology utilization; more than half employed solely hydroponic production techniques, 56% monitored light intensity, and more than 80% monitored air temperature and nutrient solution pH and electrical conductivity. Additionally, the growing environments varied from greenhouses (64%), indoors in multilayer (31%) or single-layer (7%) facilities, to hoop houses or high tunnels (29%). Overall, producers reported managing the growing environment to improve crop flavor and the development of production strategies as the most beneficial research areas, with 90% stating their customers would pay more for crops with increased flavor. Lastly, taking historical data and current practices into account, perspectives on future hydroponic CE production are discussed. These include the importance of research on multiple environmental parameters instead of single parameters in isolation and the emphasis on not only increasing productivity but improving crop quality including flavor, sensory attributes, and postharvest longevity.
Bethany A. Harris, Wojciech J. Florkowski and Svoboda V. Pennisi
Biodegradable containers of various types are available on the market and can be directly purchased by growers and homeowners. However, adoption of these containers has been slow, limiting their potential as an alternative to plastic containers. It is crucial to assess level of knowledge and use of biodegradable containers by horticultural growers and landscape service providers to help explain their slow rate of adoption by the industry. An online survey instrument was implemented to assess grower and landscaper knowledge and familiarity regarding biodegradable containers in the state of Georgia. Results indicated that 83% of horticultural growers do not purchase biodegradable containers. However, peat biodegradable containers were primarily purchased when these containers were used. Both growers and landscape service providers “neither agreed nor disagreed” that the use of biodegradable containers could improve plant growth. Growers “did not know” if using biodegradable containers “improved water efficiency.” Landscape service providers exhibited low knowledge of the wide variety of biodegradable containers available on the market as well as limited awareness of features of such containers as they pertained to plant growth.
Mohamed S. Elmongy, Xiuyun Wang, Hong Zhou and Yiping Xia
Auxins and humic acid (HA) were investigated for their roles in adventitious root induction in azalea microshoots in our previous study. To reveal the regulatory mechanisms of auxins and HA in this process, measurements of the levels of reactive oxygen species (ROS), carbohydrates, and phenolic compounds and gene expression during in vitro root development were performed. During the adventitious root induction process, ROS levels in shoots treated with auxins and HA increased compared to untreated shoots, especially during the earliest period after transfer to the media. Media supplemented with NAA experienced increases in H2O2 contents by 480%and 250%, respectively, after 7 and 14 days of culture. The phenolic compound levels were also enhanced in the shoots treated with auxins and HA, reflecting the different rooting-promoting abilities of both auxins and HA. The highest levels of total phenolic [68.6 mg·g−1 fresh weight (FW)], polyphenolic acids (121.72 μg caffic acid/g FW), and total flavonols (162.42 μg quercetin/g FW) were recorded after 21 days for NAA media, but the maximum levels of anthocyanins (49.76 μg cyanindin/g FW) were recorded after 21 days for IBA medium. Soluble carbohydrate, starch, and soluble protein levels were increased in the shoots treated with all treatments; however, the influence of NAA treatments was stronger than that of other treatments for most investigated parameters. The NAA significantly enhanced soluble carbohydrates by 30%, 37%, and 25%, respectively, at 14, 21, and 28 days compared with untreated microshoots. Expression of the POD1 gene increased in the shoots submitted to HA treatment media. Expression levels of auxin response factors (ARFs) increased with IBA- and NAA-treated explants, suggesting that ARFs may have diverse regulatory roles in adventitious root induction in evergreen azalea. Moreover, the profiles of the IAA1, IAA9, IAA14, and IAA27 transcripts were analyzed to reveal their roles in the adventitious rooting of evergreen azalea microshoots. These results indicate that auxins and HA promote adventitious root induction in Rhododendron plants through their impact on ROS, carbohydrate contents, phenolic compound levels, and expression levels of different genes related to root development in evergreen azalea plants.
Kristine M. Lang, Ajay Nair and Kenneth J. Moore
Prior work in a Midwestern United States high tunnel indicated that hybrid and heirloom tomato scions grafted to hybrid rootstock ‘RST-04-106-T’ had a minimal yield increase in the absence of soilborne disease pressure, which underscored the need for continued regional trials of alternative, commercially available tomato rootstocks. Objectives of the present study were to assess yield, fruit quality [pH, soluble solids content (SSC), total titratable acids (TTA), and firmness], and plant growth traits (plant height, stem diameter, and biomass) of grafted tomato with eight different hybrid rootstocks. ‘BHN 589’, a determinate hybrid tomato, was grafted to ‘Arnold’, ‘Beaufort’, ‘DRO141TX’, ‘Estamino’, ‘Maxifort’, ‘RST-04-106-T’, and two trial rootstocks, ‘946 TRS’ and ‘980 TRS’. Research was conducted April to September in 2017 and 2018 in a 9.1-m wide × 29.2-m long × 3.7-m tall single-poly high tunnel located at the Iowa State University Horticulture Research Station, Ames, IA. There were five plants per treatment in a randomized complete block design with five replications. Weekly harvests took place 13 times each season. ‘BHN 589’ grafted to ‘Arnold’, ‘Beaufort’, ‘DRO141TX’, ‘Estamino’, or ‘Maxifort’ had 30% to 119% more marketable fruit and had a higher marketable fruit weight by 1.3 to 4.1 kg per plant compared with nongrafted plants. Fruit quality differences were minimal in 2017 and null in 2018, as indicated by fruit pH, SSC, TTA, and the SSC:TTA ratio. The same five high-yielding rootstock treatments were the tallest, ranging from 184 to 214 cm in height. In 2017, shoot biomass of ‘BHN 589’ grafted to ‘Arnold’, ‘Beaufort’, ‘DRO141TX’, ‘Estamino’, and ‘Maxifort’ was 59 to 100 g more than that of nongrafted plants; in 2018, ‘BHN 589’ grafted to ‘Maxifort’ and ‘DRO141TX’ had the largest shoot biomass at 386 and 315 g, respectively. Overall, the results of this study indicate that ‘Arnold’, ‘DRO141TX’, and ‘Estamino’ may be comparable in performance to the widely used rootstocks ‘Beaufort’ and ‘Maxifort’ when grown under conditions lacking biotic or abiotic stress. Our results provide promising new options for Midwestern U.S. growers of high tunnel tomato who are seeking high-performing rootstocks.