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Category: VSCNews magazine

  • Establishing an Olive Industry in Florida

    Early results on low-chill varieties are expected next year from an olive research grove in Hardee County.

    By Michael O’Hara Garcia

    With weather and soils similar to the Mediterranean Basin, olives grow in Florida and throughout much of the southeastern United States.

    Currently, Florida has approximately 800 acres of olives under active cultivation by 60 to 80 individual farmers in 20 counties. The groves range from backyard hobby plots with several trees to high-density commercial operations of 100 or more acres.

    There are two modern olive mills, and several Florida nurseries propagate olive trees for fruit and ornamental purposes. A few miles over the Florida line, the Swiss agricultural management firm, Agrigrada, operates a 4,000-acre olive grove near Colquitt, Georgia, and a 300-acre olive grove and a modern olive mill serving growers near Valdosta, Georgia.

    PRODUCTION AND VALUE

    Thought to originate in the Fertile Crescent (Syria, Iraq and Iran), olive is the world’s oldest known continuously cultivated crop. For thousands of years, olives were gathered in the wild. The oil was crudely extracted by crushing fruit between stones and sieving or straining the pulp. Today, olive oil is a major commodity traded throughout the world and prized for its gastronomic and heart-healthy characteristics.

    Michael O’Hara Garcia (left) and Don Mueller show off freshly harvested olives at Greengate Olive Grove in the Florida Panhandle.

    Spain is by far the largest producer of olive oil, followed by Italy and Greece. In the United States, olives are commercially grown in California, Oregon, Washington, Texas, Arizona, Georgia and Florida. There are hobby and experimental olive plantings in Louisiana and Alabama.

    The United States consumes 80 to 90 million gallons of olive oil per year or about 1 liter per person. Domestic farmers, going at full throttle, produced less than 5 percent of total annual consumption.

    European Union market data from 2019 reveal 1 liter of olive oil sells for $5.56 or $21 per gallon. California Olive Ranch, the largest U.S. producer, retails 1 gallon of extra virgin olive oil (EVOO) for $67.36.

    Organic certification brings even higher prices. Braggs organic EVOO (imported from Greece), sells for $70 per gallon. Apollo, a top California producer, retails its Mistral and Sierra organic blends for the equivalent of around $200 per gallon. Mistral oil is based on the Ascolana, an olive variety currently producing at Greengate Olive Grove near Marianna in the Florida Panhandle.

    NEED FOR RESEARCH

    Although the olive grows in Florida, it has been considered more of a curiosity than a commercial crop. While the University of Florida/Institute of Food and Agricultural Sciences  (UF/IFAS) and Florida A&M University have olive observation plots, and agribusiness giants like Mosaic and Lykes Brothers have small experimental groves, little formal research on Florida olive cultivation is available to support industry development.

    Bill Lambert shows an olive graft in a Hardee County research plot that includes 45 olive varieties under trial.

    With the notable exception of work by the UF/IFAS Department of Entomology and Nematology, most information on the UF/IFAS Extension website dates from 2012 and is focused on California olive research and production. The Texas A&M University website provides significantly more information on growing olives in the Southeast.

    The Florida Olive Council, a non-profit grower organization, conducts some research, and the Hardee County Industrial Development Authority has several thousand olive trees at its research facility near Wauchula, Florida.

    Erroneously, some fear Florida’s humidity harms olive pollination, summer storms damage the olive crop, or disease prohibits profitable cultivation. While extreme weather impacts all crops, UF/IFAS researchers determined principal pests and diseases like olive fly, olive knot and peacock spot are not found in Florida.

    The main problem cultivating olives for commercial purposes in Florida is the availability of varieties adapted to lower latitudes where there is less winter chill. Olive varieties (Arbequina, Koroneiki, Manzanilla, etc.) commonly used in commercial operations are native to northern Mediterranean countries like Spain, Italy and Greece (38° to 41° north latitude), where 300 to 400 hours of winter chilling are common. Olives must accumulate enough chill hours between November and March to bloom. A chill hour is one hour between 32 and 45° F.

    While northern Mediterranean varieties grow throughout Florida and reliably produce in the Panhandle, they rarely bloom and fruit south of Interstate 4 (27° north latitude).

    As Florida searches for a solution to citrus greening, many acres below Interstate 4 are fallow, and farmers need an alternative crop to augment citrus. New crop ideas like industrial hemp are popular, but the U.S. Department of Agriculture (USDA) suggests returns on industrial hemp are between $116 to $475 per acre compared with Florida citrus at $2,800 per acre and California olives at $2,688 per acre.

    Responding to the need for olive research, the Hardee County Industrial Development Authority enlisted the support of the Florida Olive Council and UF/IFAS to begin research developing a market-viable, “low-chill” olive for southern Florida.

    After installing several thousand mature olive trees on an old citrus grove, the Hardee County researchers secured 45 olive varieties from the USDA olive germplasm in California. Varieties were selected based on geographic origin. The researchers wanted olives adapted to areas around 27° north latitude.

    100-year-old olive trees are growing in Ruskin, Florida.

    In June 2018, the Hardee research team grafted 45 varieties from Morocco, Tunisia, Algeria, Syria, Pakistan, Egypt, Israel and several countries in the southern hemisphere (Chile, Peru, Argentina and southern Australia) onto mature olive trees at the 20-acre Hardee County research farm near Wauchula, Florida.

    Bill Lambert, executive director of the Hardee County Economic Development Council, hopes to see some early results next year. “It takes at least three years for the grafts to mature enough to bloom, so we expect to start looking for our low-chill candidates next year,” Lambert said.

    In addition to the grafting experiment, Lambert is in discussions with UF/IFAS to explore developing a low-chill variety using a new gene-editing process called CRISPR-Cas9.

    Kevin Folta, a noted UF/IFAS genetic scientist, has begun basic research. He hopes to get the program fully funded soon. “The science is there, we just need to get to work,” he said.

  • Shallow Subsurface Drip Irrigation for Organic Growers

    Figure 1. Shallow subsurface drip irrigation is laid with a drip tape layer to a depth of 4 to 5 inches in organically grown lettuce.

    By Tim Coolong

    Subsurface drip irrigation (SDI) has been around for many years in a variety of different iterations. Most typically, SDI refers to a permanent drip system installed fairly deep (18 inches) and is used for irrigating agronomic crops such as corn or cotton.

    In many cases, vegetable crops are too shallowly rooted for a traditional SDI system, but some processing tomatoes are grown using SDI. However, a shallow SDI system, where drip tubing is buried at a depth of 4 to 6 inches (Figure 1), may be a tool that both conventional and organic vegetable growers can use.

    ADVANTAGES

    For organic growers, the ability to use shallow SDI offers two main advantages. The first is that crops can still be shallowly cultivated during the season without worrying about cutting drip tape. Second, having drip irrigation buried can allow for wetting of the root zone without excessive wetting of the soil surface. During dry seasons, this can reduce weed pressure (Figure 2).

    Figure 2. Acorn squash is grown with shallow subsurface drip irrigation (left) and surface drip (right). While this crop was grown conventionally with herbicide, notice the lack of grass weeds in the shallow subsurface drip irrigation plot compared to the surface drip. Earlier in the season, when this picture was taken, the surface drip-grown plants were slightly larger, but that difference subsided later in the season.

    Studies have also reported an increase in rooting depth and fertilizer use efficiency with shallow SDI. Many companies make drip tubing layers. University of Georgia (UGA) research has even used bed shapers/plastic layers to form beds and lay buried drip tube without using plastic mulch. In studies conducted with shallow SDI during a single season, no difference was seen in flow rate or clogging due to roots growing into the emitters. To keep costs low, 10-mil thick drip tubing was used since researchers only planned to use it for a single season. More permanent SDI systems use much thicker walled tubing.

    LIMITATIONS

    While shallow SDI can be a good tool for helping organic growers reduce weed pressure and improve cultivation, there are some potential limitations. UGA studies found that when comparing shallow SDI to surface drip, transplants with smaller (i.e., shallower) root balls initially grew quicker when planted into surface drip plots — particularly when weather conditions were dry and hot — promoting stress.

    Many of the studies were conducted on loamy soils. It is likely that the lack of capillary movement of moisture on sandy soils may limit the use of shallow SDI in those situations. Further, the shallow SDI system did not wet the surface adequately to germinate seeded crops.

    Lastly, although leaks were not common, rodents did chew into the buried drip tubing on occasion. Nonetheless, based on experience working with shallow SDI, it is a useful tool for organic vegetable farms.

    More details on the role of shallow SDI on weed management can be found online (see www.intechopen.com/books/weed-and-pest-control-conventional-and-new-challenges/using-irrigation-to-manage-weeds-a-focus-on-drip-irrigation) in “Using irrigation to manage weeds: A focus on drip irrigation.”

  • Breeding Better Cucurbits

    University of Georgia breeders developed the Orange Bulldog pumpkin.

    By Cecilia McGregor and George Boyhan

    Cucurbit crops are some of the most widely grown vegetable crops in the Southeast. However, the hot and humid climate is conducive to pest and disease development, which presents a challenge to growers. Cucurbit breeding at the University of Georgia (UGA) is focused on breeding pumpkin, watermelon and squash with excellent fruit quality and enhanced disease resistance.

    PUMPKINS

    Pumpkins are an important crop in the United States, particularly as decorations during the fall. Unfortunately, pumpkins are difficult to grow in the Southeast because of diseases. There are several diseases (particularly viruses) that affect traditional pumpkins. These diseases are transmitted by aphids in a non-persistent way. This means that as soon as the insect probes the tissue, the virus is transmitted. Control is difficult, because even with 90 to 95 percent insect control, the remaining 5 to 10 percent can effectively infect the crop.

    UGA began a breeding program in 1996 with a collection of pumpkin seeds from Brazil. Seed from both elongated and flattened fruit of Cucurbita maxima were obtained and interplanted. Putative hybrids were collected. This began several years of selection for fruit with a round shape, pleasing color and open cavity. These pumpkins have a greater degree of virus resistance compared to traditional pumpkins (C. pepo), so they produce more consistently.

    The resulting variety, Orange Bulldog, was released in 2006. Since there was no interest among seed companies, UGA has been handling sales. The primary audience for this variety is pick-your-own and roadside marketers. The vines hold up particularly well into the fall for direct marketers that “reseed” their pumpkin patch with new fruit each day.

    Pumpkin research concentrated on developing disease resistance into commercially acceptable pumpkin lines has continued at UGA.

    WATERMELON

    UGA is also actively breeding for gummy stem blight and fusarium wilt resistance in watermelon. Resistance to gummy stem blight was first described in 1962 when it was discovered in a wild relative of watermelon, Citrullus amarus. This is the same species that was used to breed the fusarium-resistant, non-harvested SP pollinizer cultivars.

    Breeding disease resistance into commercial, edible cultivars from this wild germplasm has proven difficult since the wild relative has hard, inedible flesh. This is further complicated by the fact that there are different species of the Stagonosporopsis pathogen that cause gummy stem blight and different races of Fusarium oxysporum var. niveum that cause fusarium wilt. The resistances to these diseases are quantitative, meaning that a single resistance gene does not give field-level resistance to the diseases. All these factors have delayed the development of cultivars resistant to these diseases.

    Susceptible (left) and resistant (right) watermelon seedlings infected with gummy stem blight.

    The breeding effort at UGA focuses on using modern selection methods to accelerate selection for resistance genes to speed up breeding efforts. Currently, selection is in progress for fusarium race 2 resistance and gummy stem blight resistance.

    In addition to these disease-resistance breeding efforts, UGA breeds cultivars specifically for homeowners and farmers’ markets. The focus here is on novel traits like a variety of flesh colors and rind patterns and the egusi seed trait.

    Egusi watermelon is very popular as an oilseed crop in many parts of Africa. The seeds are very high in oil (40 to 50 percent) and protein (25 percent) and are eaten as snacks or as a thickener in soups and stews. Egusi seed is large and flat with a unique fleshy outer layer that dries into a very thin seed coat that can easily be shelled. Traditional egusi watermelon has hard inedible flesh, which goes to waste. UGA is breeding egusi watermelon with edible flesh. These plants will produce fruit that pack the health benefits associated with the antioxidants in red- and orange-fleshed watermelon while also being a source of high oil and protein seed.

    SUMMER SQUASH

    In 2019, UGA started a squash breeding program. This program was launched in response to the severe yield losses experienced by Georgia growers in recent years due to whiteflies and whitefly-transmitted viruses.

    The sweetpotato whitefly (Bemisia tabaci) can directly cause yield losses in many different crops due to feeding, but an even bigger cause of yield losses are the viruses it transmits. Sweetpotato whiteflies can transmit more than a hundred different viruses. Cucurbit leaf crumple virus (CuLCrV) and Cucurbit yellow stunting disorder virus (CYSDV) are some of the most important to squash growers.

    Commercial squash cultivars have proven to be very susceptible to these viruses, and sources of resistance have not been identified. UGA, in collaboration with the University of Florida, has started large-scale evaluations of squash germplasm from all over the world in search of resistance. Several genotypes with resistance to CuLCrV and CYSDV were identified in 2019 and are now being evaluated further for use in the breeding program.

    The UGA cucurbit breeding programs are committed to developing cultivars well adapted to the Southeast, with high disease resistance and exceptional fruit quality for both large- and small-scale growers in the region.

  • Sneak Peek: October 2020 VSCNews Magazine

    By Ashley Robinson

    The October issue of VSCNews magazine covers a variety of topics, including establishing an olive industry in Florida, the potential for hops and a strawberry spotlight.

    Currently, Florida has approximately 800 acres of olives under production. Although olives grow well in Florida’s warm climate, little formal research on Florida olive cultivation is available to support industry development. Michael O’Hara Garcia, president of the Florida Olive Council, explains what it will take to establish an olive industry in the Sunshine State. 

    There is a lot of hype surrounding hops production in Florida. According to Shinsuke Agehara, an assistant professor at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Gulf Coast Research and Education Center (GCREC), Florida hops show potential. The UF/IFAS hops research goal is to develop a viable industry for Florida growers and brewers.

    Furthermore, the crop spotlight returns in the October issue of VSCNews magazine, this time focusing on strawberries.

    Sriyanka Lahiri, an assistant professor at the UF/IFAS GCREC, shares pests that are problematic to Florida strawberries and effective management strategies.

    Also, two new strawberry selections have been approved for release by UF/IFAS and are in the commercialization process. Vance M. Whitaker, an associate professor at UF/IFAS, shares the specifics on the new releases. The first release is an early short-day variety with excellent fruit

    shape and quality. The second release is a white-fruited strawberry, it is expected to be the first such variety on the market in the United States.

    Severe outbreaks of Pestalotiopsis, a new strawberry disease, has threatened Florida strawberries the last two growing seasons. Natalia Peres, a professor at UF/IFAS, shares control strategies that growers can use to manage the disease.

    If you would like to receive future issues of VSCNews magazine, click here.

  • University of Florida Blueberry Breeding Update

    Colossus has a later blooming time and very large fruit.

    By Patricio Munoz and Doug Phillips

    The University of Florida (UF) blueberry breeding program has a long history of developing superior southern highbush cultivars for the commercial blueberry industry. Beginning in 1949, the program has produced more than 40 cultivars, all of which exhibit a lower chilling hour requirement and adaptation to the higher temperatures and disease pressure experienced in Florida’s climate.

    There are several desirable traits that are the focus of blueberry breeding efforts, including fruit quality (firmness, flavor, size, color, scar size, etc.), plant vigor, disease resistance and machine harvestability (fruit firmness, detachment force, plant architecture, concentrated ripening, etc.).

    ADVANCEMENTS ACHIEVED

    Blueberry breeding programs have historically used the recurrent phenotypic selection method, which is still used today. Selection of superior candidates is based on the cross-pollination of plants with favorable traits, the progeny of which are grown out and go through a series of successive selection, with favorable plants both advancing to the next stage and being used as parents for the next breeding cycle.

    From an initial planting of 20,000 seedlings, each cycle’s population is narrowed to 10 to 15 percent, of which only a few may ultimately be released. With this method, the development of a new cultivar from cross-pollination to release can take between 10 and 12 years.

    However, since the original selections from the wild at the beginning of the program until today, significant improvement has been achieved. In 2018 the UF blueberry breeding lab demonstrated by an extensive review of the literature (Cappai et al., 2018) that firmness has been steadily improved, reaching levels that make almost all new cultivars acceptable for machine harvest, and that, in general, southern highbush cultivars are firmer than northern highbush.

    More recently, advanced methods including quantitative genetics and molecular information have been introduced, which have the potential to shorten the breeding cycle. These methods include using statistical methods to model molecular markers linked to genes associated with favorable traits. This can be done much earlier in the breeding cycle, instead of waiting until a plant becomes mature to observe whether certain traits will be present.

    Optimus is an excellent choice for machine harvesting and exhibits good production in both deciduous and evergreen systems.

    In 2019, the UF blueberry breeding lab performed a proof of concept experiment of these methods and demonstrated their feasibility (Oliveira et al., 2019). The focus during 2020 has been on optimizing these methods, which will be reported in studies to be published in the near future.

    Other areas of research in the UF breeding program include flavor perception, container production and alternative season production.

    FLAVOR PERCEPTION

    The UF breeding program recently finished performing studies to demonstrate that consumer “liking” perception can be predicted when using the unique chemical makeup of each new cultivar. The idea is to avoid bias in the selection process associated with the breeder in charge of creating and releasing new cultivars.

    In this area, discoveries have been made regarding which chemicals are favorable to the flavor perception and which ones are detrimental. This work started many years ago, and now with more information some of the findings can be validated.

    CONTAINER PRODUCTION

    Production in containers has become a global trend, primarily to produce high yields on marginal land because these soilless systems do not depend on native soil. The UF breeding program has been performing experiments as a proof of concept of this system for conditions in Florida. Results of second-year experiments show that, while these systems require high investment, they could become an attractive alternative for some Florida growers. The lab is in the process of refining the results to deliver some recommendations to growers.

    In addition, the breeding program supports and collaborates in blueberry-related research in pathology, entomology, management and pollination.

    RECENTLY RELEASED CULTIVARS

    As always, the UF breeding program is closely watching elite selections to release new cultivars. A major focus has been placed on consistency across locations and years, as well as on precociousness (the capacity to produce harvestable fruit the first year after planting).


    The most recently released cultivars from the UF program, Colossus and Optimus, have started to gain traction with growers.

    Colossus was released in 2019. It has exhibited a later blooming time with a short bloom to ripening period, and has better performance with low doses of hydrogen cyanamide. The fruit is very large to jumbo sized, is very firm, has good color and bloom and a small picking scar. Colossus has performed well in both North Central and Central Florida trial sites. The best fruit is obtained by allowing it to hang on the bush until the preferred sweet and acid balance is achieved. In 2019, the yield in North Central Florida was approximately 12 pounds per bush. Colossus can be machine harvested if needed.

    Optimus was released in 2018 as an excellent choice for machine harvesting. It has good timing for the Florida market window, with high yields and natural early leafing. Optimus has firm, medium-sized, high-quality berries. It has performed well in machine-harvesting trials and exhibited good production across Florida in both deciduous and evergreen systems. Optimus yielded 14 pounds of fruit per bush in 2019 in North Central Florida.

    Other recent releases, heavily used in the evergreen system, include Arcadia and Avanti, which were released in 2015.

    Arcadia has high yield and vigor, very low chilling requirements and disease-tolerant foliage. Several growers have reported good fruit production in the first year after planting. Arcadia has shown susceptibility to bacterial wilt (Ralstonia solanacearum), with severity varying significantly from farm to farm.

    Avanti has potential for above-average yields, with early fruit maturity, very low chilling requirements and very sweet fruit. It has shown some susceptibility to mite damage and algal stem blotch, which require good management programs.

  • Coming Soon: White Strawberries From the Wild

    By Seonghee Lee and Vance M. Whitaker

    Figure 1. A new University of Florida strawberry variety is white with a slight pink blush and red seeds when fully ripe. Photo credit: Cristina Carrizosa, UF/IFAS Communications

    The University of Florida will soon commercialize a new strawberry variety. It doesn’t have a name yet, but it is already drawing attention for a very unusual characteristic. When it is ripe and ready to eat, it is white inside and out, with a slight pink blush on the exterior and red seeds. The flavor is very different from a typical strawberry, sweet but with a pineapple-like aroma. White strawberries have been popular for some time in Japan, but this is expected to be the first white strawberry on the market in the United States.

    These unusual strawberries were not made in a lab. White strawberries are actually found in nature. Breeders have harnessed this naturally occurring trait, crossing white strawberries from the wild with modern strawberries to create something different in both appearance and taste.

    WHY IT’S WHITE

    The red color of the typical strawberry comes from pigments called anthocyanins. White strawberries produce much lower amounts of these compounds in their flesh than red strawberries. Recent research has shown that white strawberries of various types all have DNA sequence changes in a single gene called MYB10, which is involved in the synthesis of anthocyanins. These changes keep the gene from carrying out its normal function, essentially halting the chemical process in the fruit that produces red pigments.

    HOW IT WAS DEVELOPED

    In 2012, some strawberry seeds from fruit purchased in Japan were brought to the University of Florida. The seeds were sown, and a few small plants were recovered. The pollen from these plants were crossed with a Florida variety. The seedlings from this cross produced fruit that ranged from white to pink to red.

    Further crosses with Florida varieties were made, ultimately resulting in a strawberry with similar hardiness and fruit characteristics to modern varieties but with white color. Commercial trials have been promising so far. Pickers can tell when the fruit is ripe when a slight pink blush develops on the sun-side of the fruit, and when most of the seeds turn red. By 2022, these new white strawberries should be available in U.S. grocery stores.

    Figure 2. Florida strawberry varieties can be red, pink or white.
    Photo credit: Seonghee Lee
    STRAWBERRY SPECIES

    There are many different species of strawberry throughout the world, and white strawberries are naturally found within several of them.  

    Alpine Strawberry (Fragaria vesca)
    Alpine strawberries are in the species F. vesca, which is an ancient ancestor of the modern strawberry. In Europe, this strawberry is referred to as “fraises des bois” and is prized among food connoisseurs for its aroma. While most members of the species have red fruits about the size of a fingernail, the fruits of some Alpine strawberries are yellow to white in color. More information is available from the University of Florida at edis.ifas.ufl.edu/hs1326 on how to grow Alpine strawberries.

    Beach Strawberry (F. chiloensis)
    The beach strawberry is found in the wild along the Pacific coasts of North and South America. F. chiloensis is one of the most recent ancestors of the modern strawberry. Some of the beach strawberries found in South America are naturally white or pink. The fruit only grow about as large as a thumbnail and are very soft compared to modern strawberries. Some varieties of this species that are crossed between F. chiloensis and the modern strawberry (F. × ananassa) have been called “pineberries.” Some varieties of pineberries are available for home gardeners, but they are not large enough or firm enough to be produced and sold on a large scale.  

    Cultivated Strawberry (F. × ananassa)
    A white beach strawberry from Chile and another wild species from North America called F. virginiana with bright red fruits were collected by explorers and brought to Europe about 300 years ago. There they accidentally hybridized to produce the cultivated strawberry or “modern” strawberry, F. × ananassa, that we know today. Almost all the strawberries currently grown and produced in the United States are F. × ananassa. White cultivated strawberries have been bred for some time in Japan and sold at high prices as novelty items. However, white strawberries have not yet caught on as much in other areas of the world.

    See programs.ifas.ufl.edu/plant-breeding/strawberry for more information on University of Florida strawberry breeding and genetics.

  • Trialing and Developing Blackberries for Florida

    Blackberries are grown as a commercial crop in North Carolina.

    By Zhanao Deng

    Blackberry has emerged as an alternative crop in Florida. More and more Florida growers are growing or trialing blackberries for commercial production. They have indicated a dire need for suitable blackberry cultivars that can yield well and produce berries of good quality.

    PAST CULTIVARS AND RESEARCH

    In the 1950s, University of Florida (UF) released two blackberry cultivars, Flordagrand and Oklawaha. Both produced high yields of large, attractive berries, but their trailing growth habit and thorny canes made them unsuitable for commercial production.

    The University of Arkansas has maintained an active blackberry breeding program for more than five decades and has released dozens of new cultivars. Essentially all the blackberry cultivars currently grown in Florida and other Southeast states are from this breeding program.

    Some of the popular floricane-fruiting cultivars include Apache, Navaho, Natchez, Osage and Ouachita. They produce berries on second-year canes (floricanes). In 2005, the program released the first primocane-fruiting cultivars that can produce berries on the current-year canes (primocanes) as well as floricanes. Prime-Ark® 45, Prime-Ark® Freedom and Prime-Ark® Traveler have this new type of fruiting habit.

    Flowers are pollinated for blackberry breeding.

    With funding from the Florida Department of Agriculture and Consumer Services Specialty Crop Block Grant program, UF researchers began trialing these cultivars in 2017 in a blackberry orchard at the Gulf Coast Research and Education Center (GCREC). Prior to this, Shinsuke Agehara trialed Navaho, Natchez and Ouachita in wooden boxes and large containers. In his trials, Natchez outperformed Ouachita and Navaho. In the orchard trial, Osage had the highest yield among the five floricane-fruiting cultivars, with an average of 3.9 pounds of berries per plant. Among the three primocane-fruiting cultivars, Prime-Ark® Freedom had the highest yield, producing an average of 6.3 pounds of berries per plant.

    Researchers used in-row spacing of 3 feet and between-row spacing of 10 feet in the trials. With this spacing, 1,452 plants could be grown per acre. The estimated per-acre yield would be 5,663 pounds for Osage and 9,148 pounds for PrimeArk® Freedom. Natchez showed significant variability in berry yield from year to year or site to site.

    CURRENT CULTIVARS

    In recent years, the University of Arkansas blackberry breeding program has released two new floricane-fruiting cultivars, Caddo and Ponca. Based on release documents, both cultivars are high yielding, thornless, erect and produce medium to large fruit. Ponca is the sweetest cultivar released to date and has good shipping and handling traits. Both cultivars have been introduced to Florida, and a new trial is being set at GCREC to test their performance. Stay tuned for trial data in the next two years. 

    In small trials conducted in Arkansas, these cultivars had the potential to produce 10,000 to more than 20,000 pounds of berries an acre. Why do these cultivars yield much less in Florida? Researchers think the primary reason is that chilling requirements were not met in Florida, especially in Central Florida. Very much like blueberries, blackberries need a period of chilling (temperature below 45° F) to break sufficient numbers of buds and develop enough flowers so that growers can have a decent crop.

    The current blackberry cultivars grown in Florida were bred and initially selected in Arkansas, and they need 300 to 900 hours of chilling. On average, Central Florida only has about 100 to 300 hours of chilling. Without enough chilling, blackberry plants break much fewer buds, have much fewer fruiting laterals and flowers, and yield poorly with berries ripening over an extended period.        

    BUILDING A BREEDING PROGRAM

    UF trials and growers’ experiences indicate a strong need for new blackberry cultivars that are better adapted to a low-chill environment. This need prompted UF researchers to breed blackberries. The breeding program received private funding and technical support from Coastal Varieties Management. The GCREC and the UF Institute of Food and Agricultural Sciences (IFAS) Dean for Research Office provided funding to cover expenses associated with facilities.

    In spring 2015, UF researchers made the first batch of crosses to produce blackberry seeds. Newly produced seeds were treated with a strong acid to burn part of the seed coat and then they were kept cold for several months before they were germinated. The seedlings were then grown and selected in Florida. Researchers repeated this process each year since then.

    So far, more than 10,000 blackberry seedlings or young plants have been screened in Florida. Dozens of plants were selected for further trials. Shoot tips have been collected from some of the most promising plants and cultured in test tubes for rapid propagation. The first batch of tissue culture-propagated blackberry young plants from one of the selected lines was sent to growers this past June for trialing.

    Blackberry cultivar trials are underway at the Gulf Coast Research and Education Center in Wimauma, Florida.

    In the meantime, researchers have set up the first replicated trials to test the new line’s berry yield and quality. Effort is being made to expand the blackberry orchard and produce additional liners for more field trials, which is warranted to select the best adapted cultivars for Florida growers.

    As more Florida growers begin growing blackberries, they have more questions needing practical solutions. To better address growers’ needs, a UF/IFAS research and Extension team has been formed. It consists of six specialists from the GCREC and the Horticultural Sciences Department and two Extension faculty from Orange, Marion and Hillsborough counties. Team members are well experienced with berry breeding; variety selection and trials; plant management and manipulation; fertilization; disease, insect pest, nematode and weed identification and control, etc. The team has received great support from Florida growers and some seed funding from the UF/IFAS Support for Emerging Enterprise Development Integration Teams program and the GCREC.

    UF plans to produce the first blackberry production and spray guide by early 2022 and provide growers and Extension agents with more training. The goal of the team and these efforts is to facilitate the development of the Florida blackberry industry and help growers produce profitable crops sustainably.

  • Sneak Peek: September 2020 VSCNews Magazine

    The September issue of VSCNews magazine is packed with information about breeding updates and new varieties. Readers can see what’s new in strawberries, blueberries, blackberries and cucurbits.

    Breeding new varieties is a vital component to push agriculture forward. The University of Florida (UF) is a leader in the breeding industry. Recently, blackberries have emerged as an alternative crop in Florida. Zhanao Deng, a professor at the UF Institute of Food and Agricultural Sciences (UF/IFAS) shares the work that UF has done trialing and developing cultivars for the Sunshine State. According to Deng, UF plans to produce the first blackberry production and spray guide by early 2022.

    Seonghee Lee, a research assistant professor and Vance Whitaker, an associate professor, both at the UF/IFAS Gulf Coast Research and Education Center in Wimauma, discuss a new strawberry variety that UF will soon commercialize. These white strawberries, actually found in nature, are expected to be the first white strawberries on the market in the U.S.

    Patricio Munoz, an assistant professor and Doug Phillips, UF/IFAS blueberry Extension coordinator, discusses the UF/IFAS blueberry breeding program. Get the latest details on the program in his article.

    The September issue also offers something for cucurbit growers. Cucurbit crops are some of the most widely grown vegetable crops in the Southeast. However, the hot and humid climate can present a number of challenges to growers when it comes to pests and diseases. Cecilia McGregor, an associate professor and George Boyhan, a professor and Extension specialist, both at the University of Georgia (UGA), share the work being done by the UGA cucurbit breeding programs, developing cultivars that are well adapted to the Southeast.

    Finally, the September issue includes a wrap-up of the recent virtual Vegetable & Specialty Crop (VSC) Expo. Readers can get some of the highlights from the Expo educational program inside the September issue. Also, be sure to mark your calendars for the 2021 VSC Expo, returning Aug. 18-19, 2021, to the Lee Civic Center in North Fort Myers, Florida.

    If you would like to receive future issues of VSCNews magazine, click here.

  • Supplemental Fumigation Strategies for Tomato Production

    © Matthew Dicker / shutterstock.com

    By G.E. Vallad, J. Desaeger, J. Noling and N. Boyd

    Vegetable and strawberry growers have long relied on soil fumigants to contend with various soilborne pathogen and pest complexes, as part of an integrated management strategy that includes crop resistance, cultural control and pesticides. However, with the loss of methyl bromide (MBr), many growers have struggled to maintain consistent soilborne pathogen and pest control with the available fumigants.

    Much of this relates to the inability of available fumigants to disperse throughout the soil in the same manner as MBr. This is due to the physical differences in volatility, as revealed by comparing the vapor pressure and boiling points (see Table 1) of currently available fumigants to MBr and water. Volatility is the tendency of any substance to convert to a gas at a given temperature and is directly related to the substance’s specific vapor pressure, which is inversely related to boiling point.

    Figure 1. The Yetter Avenger Coulter system has a pair of coulters straddling the raised bed. Final application depth is greater than 8 inches below the soil.

    By comparing vapor pressure and boiling point values of fumigants to water, it is easier to understand why the current fumigants are referred to as volatile liquids. Vapor pressure values for Pic and 1,3-D are on average 70-fold less than MBr at 20° C (68° F), and the ITC generators are even less volatile with physical characteristics more similar to water. MBr, as a true gas, would rapidly volatilize from a liquid once applied to the soil and quickly fill available airspace within the soil profile. In comparison, all the current alternatives remain liquid following application and then slowly volatilize. These physical characteristics limit fumigant movement within the soil of the prepared, raised bed.

    Figure 2. Roots are emerging below the plastic tuck from the side of the bed.

    Unfortunately, threats from soilborne pathogens and pests are not always limited to the immediate raised bed. For example, research previously demonstrated that supplemental applications of chloropicrin along bed edges below the tuck (Figure 1) protected tomato roots emerging from the fumigated bed into non-fumigated soils (Figure 2), which subsequently reduced the incidence of fusarium wilt (Figure 3). Similarly, research demonstrated that deep-shank soil applications of 1,3-dichloropropene (Telone) (Figure 4) were necessary to manage nematode populations deeper in the soil, below raised beds, that were beyond standard in-bed fumigant applications (Figure 5).

    Figure 3. A field trial demonstrates the supplemental application of Pic 100 to bed edges compared to the grower standard of Pic-Clor 60 alone.

    FIELD TRIALS
    Many operations have problematic fields with a complex of soilborne pests and pathogens. Large replicated field trials were recently conducted to address such situations, combining both supplemental approaches in tomato fields affected by root-knot nematodes and fusarium wilt. Combinations of deep-shank Telone II, with in-bed fumigation, supplemental chloropicrin and plastic mulch [virtually impermeable film (VIF) vs. totally impermeable film (TIF)] were evaluated.

    Figure 4. A broadcast, deep-shank application of Telone II (inset shows applicator). The tractor at top is making a 16 to 18-inch application at 12 gallons per acre, followed by a disk to disrupt chisel traces (center pass) and then packed with a roller to seal the fumigant (bottom pass).

    Two fields received deep-shank applications of Telone II (12 gallons per acre) in 600-foot by 50-foot strips alternated with 50-foot non-fumigated strips across the entire field. A month later, raised beds prepared over the Telone II strips received in-bed applications of either Pic-Clor 60 (300 pounds per acre), Pic-Clor 80 (225 pounds per acre) and Pic 100 (180 pounds per acre) with supplemental application of Pic 100 along the bed edge (150 pounds per acre).

    Raised beds prepared over the non-Telone II strips received Pic-Clor 60 (300 pounds per acre) either with or without the supplemental Pic 100 along the bed edge as additional controls. Each of the described combinations were covered with both TIF and VIF plastic mulch (for a total of 10 treatments) and then planted accordingly. Each treatment plot consisted of three beds (approximately ¼ acre) and was replicated five times in each field.

    RESEARCH RESULTS
    Two weeks after deep-shank applications of Telone II, deep soil cores pulled across fumigated and non-fumigated portions of the field found total nematode levels (including parasitic Meloidogyne species) were reduced by 82 percent, from an average of 8.3 nematodes per 100 cubic centimeters of soil to 1.1 nematodes. The reduced nematode counts were further reflected at the end of the season with a 97 percent reduction in root-knot galling between deep-shank Telone II and non-deep-shank fumigated plots.

    Figure 5. A demonstration of deep-shank applied Telone II on root-knot nematodes in cucumber. Telone was applied perpendicular to raised-bed preparation. The image shows a strip where the deep-shank applicator was turned off.

    Supplemental Pic applications reduced average root gall ratings 24 percent and reduced average fusarium wilt incidence by 47 percent. Unexpectedly, deep-shank Telone II applications had the greatest statistical effect on fusarium wilt, reducing disease incidence by 66 percent, from 19.4 to 7.5 percent average incidence across all treatments. In-bed fumigants also had a significant but minor effect on average root gall ratings and fusarium wilt, with in-bed Pic-Clor 60 and Pic-Clor 80 performing better than Pic 100.

    Statistically, mulch had no effect on nematode gall ratings, fusarium wilt or yields. In-bed fumigation had numerical but no statistical effect on tomato yields. A replicated lab study further demonstrated the fungicidal activity of 1,3 dichloropropene (Telone II) against Fusarium oxysporum f. sp. lycopersici. Several other studies have reported similar findings for 1,3 dichloropropene against soilborne pathogens and for chloropicrin against nematodes.   

    CONCLUSION
    These findings further support the notion of developing supplemental fumigation strategies that target soilborne pests and pathogens at their source. These supplementary approaches are meant to be prescriptive in nature, based on the specific soilborne pest or pathogen problems observed in fields.

    Current and future research will address the frequency of supplemental fumigation and the use of other fumigants, as well as reducing in-bed application rates to help offset the cost of supplemental fumigation. Improvements in available post-plant fungicides and nematicides may also change fumigation strategies, as well as the availability of crop varieties with improved tolerance to soilborne pathogens and pests. Parties interested in participating in such studies are welcome to contact Gary Vallad at gvallad@ufl.edu or 813-419-6577.

  • Bioengineered Sentinel Plants Could Help Protect Future Crops

    Illustration by Snow Conrad

    By Jenelle Patterson

    As a plant molecular biologist, I often hear tales of gardening mishaps or plant-related tidbits from my friends and family.

    A few years ago, a friend excitedly relayed her experience at a Niagara wine tour, where the tour guide explained that they grow rose bushes at the end of each row not only for aesthetics, but as early warning systems for pests and diseases (such as powdery mildew). This piqued my curiosity, and I discovered that using plants as biosensors or sentinels is not a modern concept. Roses have been used this way for centuries.

    However, the use of roses as sentinels has disadvantages:

    1) Some pests or pathogens that target grapes do not affect roses.

    2) By the time a rose shows signs of a fungal infection, it may be too late to protect the grapes.

    Most modern vineyards employ more sophisticated integrated pest management strategies (e.g., forecasting disease outlooks using weather reports and tracking confirmed cases). But, this canary-in-a-coal-mine approach of using plants as warning systems still may prove useful, especially where other types of testing are unavailable or costly.

    ADDRESSING SENSITIVITY AND SPECIFICITY

    A diverse array of agricultural and human health hazards (pathogens, heavy metals, herbicide residues, radioactivity, even explosives, to name a few) could conceivably be detected using sentinel plants. But we first need to address the reasons why roses fall short: sensitivity and specificity.

    The first attempts to bioengineer sentinel plants began in the late 80s with the discovery and development of reporter genes (think of them as biological red flags). By the 90s, engineered plants were designed that could detect genotoxins (chemicals or UV-C light that cause DNA mutations). Prolonged exposure to genotoxins causes mutations in the plants, which were measured by staining the plant tissue with a chemical that turns cells blue if the reporter gene is mutated.

    These plants could detect heavy metals, herbicides and radioactivity just as effectively as conventional methods that use animals or chemical analysis. And these sentinel plants were cheaper, required less maintenance and avoided the ethical concerns of using animals. Despite being a big step in the right direction, prototypes had the same issues as their natural rose counterparts: The tests took weeks to months of exposure (sensitivity) and could not be used to identify the genotoxin, only to indicate that one was present (specificity).

    Bioengineering has made huge progress in the past decades as scientists develop new technologies and a better understanding of how plants naturally detect and react to changes in their environment. Plant researchers are beginning to rethink biology in terms of computer programming, adopting concepts like modular system design and logic gates.

    Simply put, biological components are being treated like modular parts used to build an input/output system. Plants and all living organisms use this kind of system already. A signal is detected (e.g., getting chewed on by a bug), that information is relayed in a game of telephone by enzymes and signal molecules, generally ending in the nucleus (the control center of the cell), which flips a genetic switch to bring about some response. The power of bioengineering is the ability to design a tunable system, one that is sensitive to a specific input.

    In 2011, researchers tested this principle by building a TNT-detector plant. They integrated genetic parts from bacteria into a plant’s natural stress-response pathway. Their creation could sniff out and signal the presence of soil- or airborne TNT molecules (input) by causing leaf de-greening (output), and at equivalent levels to bomb-sniffing dogs. This landmark study was just the beginning. It demonstrated the potential for bioengineered sentinel plants to address the sensitivity and specificity limitations of their natural predecessors.

    RESEARCH ADVANCEMENTS

    Researchers have since been identifying and redesigning biological parts to build complex logic gates. Early bioengineered systems were only capable of binary on/off states. Building more complex systems by adding modular components that work together gives the plant the ability to make more nuanced ‘decisions’ (like computer logic gates: react to this and/or this, but not to that). This can reduce false positives and allow for more sensitive detection. Different reporter outputs can also be used to reduce testing times and avoid destroying the sentinel plant, such as engineering plants to produce fluorescent proteins in their leaves, which is easily visible under a UV lamp.

    Researchers still have more work to do to make sentinel plants reliable enough for routine use in agriculture. But it’s not hard to foresee a future where genetically trained roses are a critical part of modern integrated pest management, and not just a nice story to tell guests on a wine tour.