The American cranberry (Vaccinium macrocarpon Ait.) was genetically transformed with the bar gene, conferring tolerance to the phosphinothricin-based herbicide glufosinate. Plants of one `Pilgrim' transclone grown under greenhouse conditions were significantly injured by foliar treatments of 100 mg·L-1 glufosinate, although the injury was less severe when compared to untransformed plants. However, the same transclone grown outdoors in coldframes survived foliar sprays of 500 mg·L-1 glufosinate and higher, while untransformed plants were killed at 300 mg·L-1. Actively growing shoot tips were the most sensitive part of the plants and at higher dosages of glufosinate, shoot-tip injury was evident on the transclone. Injured transgenic plants quickly regrew new shoots. Shoots of goldenrod (Solidago sp.) and creeping sedge (Carex chordorrhizia), two weeds common to cranberry production areas, were seriously injured or killed at 400 mg·L-1 glufosinate when grown in either the greenhouse or coldframe environment. Stable transmission and expression of herbicide tolerance was observed in both inbred and outcrossed progeny of the above cranberry transclone. Expected segregation ratios were observed in the outcrossed progeny and some outcrossed individuals demonstrated significantly enhanced tolerance over the original transclone, with no tip death at levels up to 8000 mg·L-1. Southern analysis of the original transclone and two progeny selections with enhanced tolerance showed an identical banding pattern, indicating that the difference in tolerance levels was not due to rearrangement of the transgene. The enhanced tolerance of these first generation progeny was retained when second generation selfed progeny were tested.
Plant establishment and lateral growth of glyphosate-resistant creeping bentgrass [Agrostis stolonifera (synonym A. palustris)] were assessed to determine if the insertion of the construct conferring herbicide tolerance affected establishment rate or aggressiveness characteristics in unmowed situations. Field studies were carried out in Michigan, Illinois, Ohio, and Oregon in 2000 and 2001 to examine the relative lateral growth of several transformed lines of creeping bentgrass, non-transformed controls, and cultivar standards. Vegetative plugs of creeping bentgrass were transplanted into replicated bare-soil plots and irrigated as needed to prevent moisture stress for an initial 6-week period. Measurements of maximum and minimum stolon spread, percent cover, and stand density for each entry were made in the field at all locations during 2000 and 2001. Few statistical differences (P = 0.05) in establishment and lateral growth were observed between individual lines of transgenic creeping bentgrass, non-transformed control lines, and standard cultivars and over a 15- to 18-month period. Overall, lateral growth and establishment rate of transgenic lines were similar to their non-transformed parent and the standard cultivars tested. Transgenic creeping bentgrass lines should have no greater potential for lateral growth than conventional creeping bentgrass cultivars currently in use.
Ornamental grasses are popular landscape plants and often encounter turf encroachment or other grass weed problems. Several postemergence grass herbicides are available for use in turf and ornamentals and herbicide tolerance information is needed for ornamental grass species. Fifteen ornamental grasses including species from the genera Calamagrostis, Cortaderia, Eragrostis, Erianthus, Miscanthus, Sorghastrum, Spartina, Panicum and Pennisetum were field planted in Clemson, SC in May 1989 and Festuca species in November, 1989. Herbicide treatments were fenoxaprop-ethyl, fluazifop-P and sethoxydim at 0.4 kg a.i.·ha-1 applied 4 weeks after planting and an untreated control. Height and injury evaluations were taken at weekly intervals and plants were harvested 10 weeks after treatment. Fenoxaprop-ethyl treated Calamagrostis and Festuca species treated with all herbicides were the only treatments that were the same as untreated controls in terms of % injury, height and dry weight. Three ornamental Calamagrostis species were evaluated in a greenhouse study to determine the level of tolerance to fenoxaprop-ethyl at 0.4, 0.8, 1.6 and 3.2 kg a.i.·ha-1. No visual injury symptoms were seen on any treatments as compared to untreated controls but growth rates of the youngest leaves did vary among species shortly after treatment.
Buckwheat has historically been used to suppress weeds and improve soil condition, but many of the tricks to success have been lost to history. Buckwheat is inexpensive and particularly effective in short windows between crops. We are documenting the techniques of existing experts and complementing that with research. We surveyed northeastern vegetable and strawberry growers to identify what information they need in order to feel confident that they could succeed with a buckwheat cover crop. Top questions include seed availability, types of weeds controlled, relation to other cover crops, volunteer management, and herbicide tolerance. One question tested experimentally was how to establish a full stand with minimum cost. We tested the minimum tillage requirement following pea harvest. No-till resulted in good emergence but slow growth, and dominance by weeds. Disk incorporating the pea residue resulted in excellent growth, which was not further enhanced by chisel plowing before disking. Buckwheat seedlings are intolerant of waterlogging, so deeper tillage may be important in wet years. Sowing buckwheat immediately after tillage resulted in emergence of 35%, leaving gaps large enough for weeds to grow. Waiting 1 week gave an 80% stand and complete weed suppression. Waiting 2 weeks also gave an 80% stand, but weed growth was advanced enough that weed suppression was incomplete. Therefore, a buckwheat cover crop following early vegetables requires light tillage to permit root growth, and up to a week of decomposition. If those provisions are made, complete weed suppression is obtainable.
The effect of bentazon on hosta (Hosta fortunei Tratt. cv. Hyacinthina), daylily (Hemerocallis L. cv. Sammy Russell), and yellow nutsedge (Cyperus esculentus L.) diffusive resistance and net photosynthesis was determined to screen for resistance to bentazon, a herbicide. Measurements of diffusive resistance and net photosynthesis were taken over 99 hours after treatment. Bentazon application increased diffusive resistance in yellow nutsedge 4 hours after treatment. In hosta and daylily, diffusive resistance increased by 24 hours; however, at 48 hours, treated plants responded the same as controls. Net photosynthesis was inhibited in yellow nutsedge within 4 hours after treatment, and the plants did not recover when measured after 4 days. Hosta net photosynthesis decreased after 24 and 48 hours, but net photosynthesis returned to the level of control plants after 4 days. Daylily net photosynthesis was not affected by bentazon application. No visual injury was detected from bentazon treatment in hosta or daylily, but nutsedge was severely injured. For rapid screening of herbicide tolerance, it may be possible to use photosynthetic measurements to determine susceptibility to bentazon. Chemical name used: 3-(1-methylethyl)-(1H)-2,1,3-benzothiazothiadiazin-4(3H)-one 2,2-dioxide (bentazon).
Five greenhouse and two Geld experiments were conducted to evaluate tissue culture-propagated (TC) raspberry (Rubus idaeus cv. Heritage) sensitivity to preemergent herbicides. Plant performance was measured by plant vigor, above-ground fresh weight, root development, and primocane number. Simazine and oryzalin caused significant injury to newly planted TC raspberry plants in greenhouse and field experiments. The severity of injury was generally linear with respect to herbicide rate, but no appreciable differences in injury were observed between the granular and spray applications. Napropamide wettable powder caused some foliar injury, but plants recovered within one growing season and growth was equal or superior to the hand-weeded controls. The granular formulation of napropamide produced similar results, but did not cause the initial foliar burn. Pre-plant dipping of roots into a slurry of activated carbon did not prevent simazine or oryzalin injury, but injury was reduced when herbicide applications were delayed. Simazine applied 4 weeks after planting was not Injurious, and oqzalin applied 2 or 4 weeks after planting caused some foliar injury, hut no reduction in plant fresh weight. Delayed treatments of napropamide increased foliar injury. Herbicide tolerance of tissue-cultured plantlets appeared to be less than that of conventionally propagated plants. Chemical names used: N,N-diethyl-2-(1-napthalenyloxy)propanamide (napropamide), 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin), 6-chloro-N,N'diethyl-1,3,5-triazine-2,4-diamine (simazine).
Many seed companies are using plant biotechnology as a valuable extension of conventional plant breeding with the goal of providing breeders with novel biological traits. The application of biotechnology allows scientists and breeders to make precise changes during the process of germplasm improvement. Many of the first improvements achieved using transgenic plants have involved the transfer of input traits. Some of these traits include, insect resistance, nematode resistance, disease resistance, and herbicide tolerance. For example, the insertion of a gene that produces the crystalline toxin from Bacillus thuringeinsis has led to the production of transgenic plants that are resistant to insects from the Order Lepidoptera. The transfer of coat protein genes from plant viruses has lead to the development of transgenic crops that are resistant to the virus from which the gene or genes were isolated. Various strategies have been developed that allow transgenic plants to tolerate applications of herbicides that allows for improved weed control. In addition to input traits, other strategies are now being used that are directed at improving output traits. These include such traits as enhanced shelf life, ripening control, altered oils, and superior processing characteristics. At Seminis Vegetable Seed Co., we are currently developing transgenic plants with enhanced input as well as output traits. We have an active program using pathogen derived genes to develop virus resistance cultivars in a range of crops including, tomato, cucurbits, and peppers. Using this approach, we have been able to develop plants with multiple virus resistance by transforming germplasm with constructs containing stacked genes. Seminis is currently marketing a hybrid squash variety with resistance to two major virus pathogens. Another major goal for Seminis is implementing biotechnology to improve various aspects of fruit quality including viscosity, color, softening, and shelf life. Through our collaboration with Zeneca we have developed a high viscosity tomato, which was produced by suppressing endogenous levels of polyglacturonase. This processed food product is currently on the market in the United Kingdom.
The promise of biotechnology has been slow to be realized, but some commercialized products are finding their way to supermarket shelves. Nevertheless, the future potential remains in the realm of speculation and may be on the verge of delivering some incredible benefits. Since the world population growth is predicted to double in the next 50 years, primarily in developing nations, food resources will become critical. In view of this prediction, we may need every trick in the book to feed the masses, which means either more land (wetlands, forests, and rain forests) will fall to the plow or there will need to be an increase in yields. Concurrently, a decrease in postharvest losses would also be crucial. Various authorities have estimated that 25% to 80% of harvested fruits and vegetables are lost due to damage and spoilage. Early biotech successes were developing plants with enhanced insect resistance (cotton, corn, and potato) and virus resistance (squash and papaya) and improved herbicide tolerance (cotton, soybean, and corn). The only commercialized transgenic fruit engineered for improved postharvest quality so far is the tomato. Future goals for biotechnology include increasing yield, extending shelf life, improving nutritional and flavor quality, and producing specialty proteins or other compounds. Genetically engineered food, however, has met rancorous resistance in Europe, New Zealand, and elsewhere; although, it is somewhat tolerated in the U.S. The U.S., Canada, and Japan lead the world in biotech acreage, with biotechnology accounting for 40% of cotton, 39% of soybeans, and 20% of corn acreage in the U.S. and 73 million acres worldwide.
safe and cost-effective weed management protocol for seashore dropseed establishment, characterization of herbicide tolerance is essential. In this study, the tolerance of seashore dropseed to applications of pre- and postemergence herbicides and table
mesosulfuron as compared with ‘Florida Fantasy’. Further research is warranted to investigate the physiological basis for SU herbicide tolerance and selectivity among caladium cultivars. Differential cultivar responses to SU herbicides have also been reported