The majority of this use is in horticultural crops with California and Florida together accounting for 80% of the 35 million pounds applied each year for preplant fumigation . Many genes are available that potentially could be used to enable alternative weed-control strategies. Horticultural crops are also limited in the numbers of herbicides registered for use. Loss of registration for a few key chemicals could markedly limit grower options, making crop resistance to broad-spectrum herbicides more critical. Resistance to fungal and bacterial diseases would also be desirable, as in some areas extensive use of pesticides is currently undertaken for their control. As for herbicides, it is also difficult to maintain registrations for minor crops grown on smaller acreages, which are primarily horticultural. Biotech strategies are being developed that could provide broader spectrum disease control and reduced dependence upon chemical pesticides . Resistance to viral diseases would be valuable in many horticultural crops, as there are few other options for control, and methods for engineering virus resistance are well established. Tree fruit, nuts and grapes. Research is well under-way to build a robust platform of technologies to utilize genomics in the discovery of useful traits for trees . Transformation technology has been developed and trait evaluation is under way on apple, almond, peach, citrus, walnut, pear, plum, grapevine and persimmon. Good progress has been made in developing resistance to codling moth and fire blight in apple, plum pox virus in plum/Prunus, crown gall and codling moth in walnut, citrus tristeza virus in citrus and Pierce’s disease in grapevine. Engineering of resistance to codling moth in apple to reduce the use of chemical pesticides has advanced to the point of commercial interest in product development. Work is also under way to develop productivity and quality traits such as modified sugar metabolism and ripening in apple and he pivotal year in the history of Hawaii’s papaya industry was 1992.

In May 1992, papaya ring spot virus was discovered in Puna on Hawaii Island, where 95% of Hawaii’s papaya was being grown. Just one month earlier,nft hydroponic system a small field trial to test the resistance of a transgenic papaya line had been started on Oahu Island, where papaya production had previously been devastated by PRSV. The timely commercialization of PRSV resistant transgenic papaya trees has revived Hawaii’s papaya industry and provides an example of the challenges and opportunities for horticultural biotechnology. In 1945, D.D. Jensen made the first report in Hawaii of PRSV, a potyvirus that is transmitted non-persistently by aphids . PRSV was first discovered on Oahu and caused such severe damage that the papaya industry was relocated to Puna in the late 1950s and early 1960s. The papaya industry expanded and prospered inPuna, primarily because PRSV was absent. However, by the 1970s PRSV was found only about 19 miles away in Hilo, and the Hawaii Department of Agriculture took rouging and quarantine actions to prevent its spread to Puna. In 1986, efforts were initiated to develop a virus-resistant transgenic papaya by transforming commercial lines of Hawaiian papaya with the coat protein gene of PRSV from Hawaii. By 1991, the team of Maureen Fitch, Jerry Slightom, Richard Manshardt and Dennis Gonsalves identified a transgenic line that showed resistance under greenhouse inoculations. These plants were micropagated and established in a field trial in Waimanalo on Oahu in April 1992. By December 1992, it was evident that line 55-1 was resistant under field conditions. From the 1992 field trial, two cultivars were developed and designated ‘SunUp’ and ‘Rainbow’. ‘SunUp’ is homozygous for the coat protein gene while ‘Rainbow’ is an Fl hybrid of ‘SunUp’ and the non-transgenic ‘Kapoho’. Unfortunately, by October 1994, PRSV had spread throughout much of Puna, causing HDOA to abandon rouging efforts to slow the spread of PRSV. The race was on to move the transgenic papaya line to commercialization. A 1995 field trial in Puna conclusively showed that ‘SunUp’ and ‘Rainbow’ were resistant under prolonged and heavy disease pressure.

The U.S. Department of Agriculture’s Animal Plant Health Inspection Service deregulated transgenic line 55-1 in November 1996, and the U.S. Environmental Protection Agency deregulated it in August 1997. The consultation process with the U.S. Food and Drug Administration was completed in September 1997. Licenses to commercialize the transgenic papaya were obtained by the Papaya Administrative Committee in Hawaii by April 1998. A celebration was held to mark the debut of the transgenic papaya on May 1, 6 years after PRSV was discovered in Puna and after the first field trial of line 55-1 was initiated. The transgenic fruit is currently sold throughout the United States. In 1992, Puna produced 53 million pounds of papaya, but by 1998 production had dropped to only 26 million pounds as PRSV spread throughout the region. Since then, the transgenic varieties have enabled farmers to reclaim infected areas and in 2001, Puna produced 40 million pounds of papaya. The resistance has held up remarkably well and remains stable after 5 years of extensive plantings. Hawaii also exports papaya to Canada and Japan. The transgenic papaya was recently deregulated in Canada, which is a relatively small market for Hawaii. The main challenge is deregulation of transgenic papaya in Japan, where Hawaii sells about 30% of its papaya. Presently, non-transgenic papaya must also be produced in Hawaii to satisfy the Japanese market, but this is increasingly difficult due to the disease pressure. Exporters face added expenses to guard against the accidental shipment of transgenic papaya to Japan. In December 2000, Japan’s Ministry of Agriculture, Forestry and Fisheries approved line 55-1, and the Ministry of Health, Labor and Welfare is reviewing a recently submitted petition for deregulation. Anticipated approval of transgenic papaya in regulation of self-incompatibility in almond and other Prunus species. Some deployment strategies for transgenic trees are also being developed, such as the use of transgenic trees as “trap crops” to control insects in conventional orchards and the use of transgenic root stocks to control diseases and pests in non-transgenic scion varieties . The latter approach avoids the task of transforming many varieties of a particular tree crop and in the future may be used to regulate quality and productivity traits.Although more difficult technically and therefore not close to market, there are many potential opportunities for enhancing the nutritional value or consumer appeal of horticultural products through biotechnology. In addition to modification of ripening, projects to increase the content of vitamins, minerals or nutraceuticals in horticultural products are in progress .

The development of Golden Rice with enhanced betacarotene in the grain demonstrated the potential for biotechnology to increase nutritional value. Whether such products will have sufficient consumer appeal in fully developed markets to drive their commercialization remains to be seen.Since floricultural and ornamental plants are grown for aesthetic or other nonedible purposes, there may be less potential for public concern about GE varieties than there has been with biotech food crops. Flower color. Several ornamental plants, including carnation, rose and gerbera, have been engineered for modified flower color. Research has focused on the manipulation of either anthocyanins or carotenoids,hydroponic nft system with the intent of creating a wider range of flower colors than occurs naturally, as well as to produce natural dyes for industrial purposes . Florigene is selling Transgenic Moon series carnations engineered for dark violet-purple color around the world. The varieties are developed in Australia and flowers are produced primarily in South America for marketing in the United States and Japan. Floral scent. Putting the scent back into flowers that have “lost” this trait over years of traditional hybridization and selection, or creating new fragrances in plants, has considerable potential and appeal. Research on genes controlling the different biochemical pathways for various floral fragrances is being conducted on wild plants and on crops such as snapdragon, petunia and rose . Plant size. Currently, growth regulating chemicals are applied to ornamental plants to inhibit gibberellic acid synthesis and reduce plant height during crop production. Many newly introduced ornamental species are receiving particular attention via conventional breeding for dwarf plants because their natural habits do not fit into marketing systems requiring compact plants. The manipulation of GA metabolism via biotechnology has the potential to produce ornamental and flowering plants with reduced-height phenotypes . The development of lawn grasses that require significantly less frequent mowing is another obvious application.Leaf life. Engineering of plants to delay leaf senescence is also being pursued in ornamental crops. For years, ornamental breeders have selected new cultivars of plants with more attractive “stay green” phenotypes. Cytokinins are plant hormones well known to delay the loss of chlorophyll in leaves; using biotechnology, targeted expression of genes involved in cytokinin synthesis is now possible. When a gene promoting cytokinin biosynthesis is inserted into plants in conjunction with a regulator that turns the gene on only Fruit and vegetable crops are under constant pressure from pests such as weeds, viruses, fungi, bacteria, insects and nematodes. If not controlled, many of these pests substantially lower yields. Successful agricultural production has depended on the use of pesticides for 100 years, and, yet, losses still occur due to certain pests that are poorly controlled. Some crops incur high costs for hiring laborers to hoe weeds because there are no effective herbicides. In addition, new pests routinely arrive for which effective controls have not yet been developed. Agricultural researchers continuously seek out new methods to control pests, including biological agents, new chemicals and plant resistance through classical breeding. Biotechnology also offers a solution in some situations where traditional methods are ineffective or costly. Numerous researchers around the world are investigating biotechnological solutions to pest problems of horticultural crops.

In 2002, the National Center for Food and Agricultural Policy released a study of current and potential biotechnological approaches to pest management in a wide array of crops . Current plantings. The study identified three varieties of transgenic fruits and vegetables that are currently planted on small acreages in the United States: virus-resistant squash is grown on 5,000 acres in the Southeast, to prevent late-season losses to mosaic viruses; virus-resistant papaya is widely planted in Hawaii ; and insect-resistant sweet corn is planted on a small number of acres and has reduced use of insecticide sprays.Withdrawn varieties. Two transgenic horticultural varieties were available for a short time in the United States but were withdrawn due to marketing concerns. Insect- and virus resistant New Leaf potatoes were planted on 4% of the nation’s acreage in 1999 and were credited with reducing insecticide use. If the transgenic varieties had not been withdrawn due to processor resistance they could have been planted extensively in the Northwest, reducing insecticide use by 1.4 million pounds. In 1999, the U.S. Environmental Protection Agency granted Wisconsin sweet-corn growers emergency permission to spray herbicide-tolerant varieties . The transgenic varieties were not widely planted due to marketing concerns and growers have not reapplied for the use despite continued production losses. Crops currently being tested. Numerous fruits and vegetables have been transformed through genetic engineering and are being tested for their potential role in improving pest management. For example, University of Florida researchers are testing virus resistant tomatoes as a substitute for the extensive insecticide spraying currently utilized to control insects vectoring geminiviruses. In California, herbicide-tolerant processing tomatoes have been tested and have the potential to reduce grower costs by $30 million and replace the use of 4.2 million pounds of fumigants. UC researchers have tested herbicide tolerant lettuce that could reduce herbicide use by 140,000 pounds a year. Herbicide-tolerant strawberries could save Eastern growers several hundred dollars per acre in weed-control costs. Nematode-resistant pineapple is being developed at the University of Hawaii to replace 1.4 million pounds of fumigants. Insect-resistant broccoli developed at Cornell University could improve yields in years of heavy insect pressure. Virus resistant raspberries developed by U.S. Department of Agriculture researchers in the Northwest could help combat bushy dwarf virus, which is present in 80% of Northwest plantings. And transgenic apples resistant to fire blight bacteria have been developed and tested at Cornell University; the transgenic varieties would replace the use of antibiotics, which are used to kill the bacteria on 25% of U.S. apple acreage. Emerging pests. Several research programs are focused on biotechnological approaches to control emerging pest problems.