Testing Tree Seeds for Vigor: A Review
F. T. Bonner
This review examines the use of vigor tests for tree seeds. It suggests that precise evaluations of these tests and their application with seeds of woody plants is not yet possible. This is due to the wide genetic variation, primarily manifested in variable maturity and dormancy, that exists in most tree seed lots. Sensitive measurements of germination rate during standard germination tests have proved to be just as good, if not better, than any vigor test in judging the quality of seed lots. Accelerated aging, leachate conductivity, and germination rate all show promise, but extensive tests of field emergence are needed to validate the laboratory test procedures and interpretation.
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Initiatives to Improve the International Seed Health System: A Review
Seeds can be efficient means of introducing plant diseases into geographical regions by transmitting seed-borne plant pathogens. Numerous examples exist of imports of diseased seeds that have had serious economic consequences, such as karnal bunt (Tilletia indica Mitra) from Asia to Mexico and the US (Brennan et al, 1992; Neergaard, 1977). The need for international quarantine controls to prohibit introductions of economically important plant diseases by seeds is clearly justified.
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Soybean Genetic Resistance and Benomyl for Phomopsis Seed Decay Control
RogerW. Elmore,* Harry C.Minor, and Ben. L. Doupnik, Jr.
Phomopsis seed decay (PSD) is the seed infection phase of an important soybean [Glycine max (L.) Merr.] disease complex and is caused by several species of Phomopsis and Diaporthe. The complex (which also includes pod and stem blight and stem canker) reduces seed quality in all major soybean growing areas of the world. Farmers use cultural and chemical methods to partially control PSD. Genetic resistance is an important defense against plant disease and an important alternative to chemical control.
Physiology and Biochemistry of Recalcitrant Guarea guidonia (L.) Sleumer Seeds
K. F. Connor* and F. T. Bonner
Investigations of recalcitrant, or desiccation-sensitive, seeds have as yet failed to identify the causes of this phenomenon. Experiments with Guarea guidonia (L.) Sleumer (American muskwood) were initiated to determine the effects of desiccation on the physiology and biochemistry of the seeds of this tropical tree species. Seeds were air-dried at room temperature for 7 days. At intervals, germination was tested, moisture content determined, and lipids extracted.
Detection and Removal of Off-colored Bean Seeds by Color Sorting
P. C. Lee, D. H. Paine, and A. G. Taylor*
Off-colored seeds are routinely present in a seed lot, and subtle differences in seed coat color are most easily observed in white-seeded crops. Off-colored seeds not only affect the general appearance of a seed lot, but also may be indicative of decreased seed quality. Seeds of a white-seeded cultivar of snap bean (Phaseolus vulgaris L.) were manually sorted into brown, tan, green and white fractions under white light. Germination tests were conducted on each sorted fraction; nonsorted beans served as the control.
Corn Cold Test Germination as Influenced by Soil Moisture, Temperature, and Pathogens
J. M.Woltz,* D. M. TeKrony, D. B. Egli, and P. Vincelli
The cold test is the most popular vigor test for corn (Zea mays L.) seed; however, standardization among seed testing laboratories has not been accomplished. This experiment determined the effect of soil moisture, cold period temperature and soil-borne pathogens on the germination of treated and untreated seed lots of five corn hybrids using the ‘shoe box’ cold test method.
Effects of Desiccation on the Recalcitrant Seeds of Carapa guianensis Aubl. and Carapa procera DC.
K. F. Connor,* I. D. Kossmann Ferraz, F. T. Bonner, and J. A. Vozzo
This study was undertaken to determine if the seeds of Carapa guianensis Aubl. and Carapa procera DC. undergo physiological, biochemical, and ultrastructural changes when they are desiccated; and to find if these changes can be used to monitor viability in Carapa. Seeds were air-dried at room temperature for 7–11 days. Samples were taken at frequent intervals and germination was tested, moisture determined, lipids extracted, and samples taken for electron microscopy.
Leaf Vernation Test for Perennial Ryegrass
Don F. Grabe*
A supplementary test procedure is described for improving the accuracy of the fluorescence test for perennial ryegrass. In practice, a fluorescence test is conducted as usual. Fluorescent seedlings are then transplanted and grown to the 3- to 4-leaf stage to be identified on the basis of leaf vernation.
Non Peroxidase Oxidation of Guaiacol
Richard A. Vierling, Reid G. Palmer and James R.Wilcox
The peroxidase test for soybean [Glycine max (L.) Merrill] is a standard assay used in the identification of soybean cultivars. Cultivars are divided into two groups based on the presence of either high or low seed coat peroxidase activity. High or low activity is based on the observed color change associated with oxidized guaiacol.
A Bioassay for Detection and Quantification of Xanthomonas campestris in Sunflower Seeds
R. S. Romeiro,* A. B.Moura and A. J. A.Monteiro
The combined techniques of extraction and plating on culture medium with hypocotyl pricking inoculation was studied for detection of Xanthomonas campestris in naturally infected sunflower seeds. The method was efficient to detect the pathogen and allowed quantification of viable bacterial cells in association with two seeds lots, estimated as, respectively, 3.096 x 107 c.f.u. and 2.088 x 106 c.f.u. per gram of seeds. Parallel assays by direct planting indicated a percentage of transmission of, respectively, 18% and 5%. This is a simple method adaptable to routine testing of many samples.
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Rapid Germination of Eastern Dogwood (Cornus florida L. cv. Small) using Embryo Extraction, Cut Cotyledons and Gibberellic Acid
J.E. Laufmann* and L.E.Wiesner
Normal seed germination of Cornus florida L. cv. Small requires a moist prechill treatment at 3–5°C for 90–120 days followed by 20–30 days of germination at 20–30°C. Expected germination using this procedure is 30–45%. This low germination percentage is primarily due to slow seedling growth and high fungal contamination. To decrease the prechill period and increase germination, seeds from three locations were evaluated using embryo extraction, cut cotyledons, and gibberellic acid (GA3) treatments.
Lactic Acid Clearing of Grass Seeds in Tetrazolium Tests
Don F. Grabe* and John A. Peters
Lactophenol is routinely used as a clearing agent for grass seeds in the tetrazolium test. Because of the toxic nature of lactophenol, a non-toxic replacement is highly desirable. Lactic acid was compared with lactophenol in over 200 samples of grass seeds, including many varieties of six seed kinds. Seven analysts participated in rating the two reagents for clearing ability, safety, ease of preparation, odor, and glare. In all factors evaluated, lactic acid was equal to or superior to lactophenol.We conclude that lactic acid may be substituted for lactophenol as a clearing agent for grass seeds in the tetrazolium test.
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