Search Results

Abstract

Physical characteristics measured individually for each lettuce (Lactuca sativa L.) seed and its embryo were significantly correlated with seedling and plant growth (vigor) up to a certain stage, possibly heading, after which the correlations diminished. Embryo physical measurements, although slightly better correlated with subsequent vigor than seed (achene) physical measurements, were highly correlated with those of the whole seed.

Of the 5 physical measurements studied, all but length were found to be associated with early vigor. Thorough statistical analyses place seed and embryo physical characteristics in a consistent and significant order in determining vigor: weight > thickness > density (as measured by an air column) > width > length.

Several studies with annual crops have shown that large seeds improve percent germination, seedling growth, and uniformity, yield, seedling vigor, and stress tolerance. Little information is available on the influence of seed size on the resulting seedlings of woody plant species. Cercis canadensis L. seeds were divided into large and small seed size fractions and the seeds scarified, stratified, and planted. A larger percentage of large seeds germinated than did small seeds. Seedlings from large seeds had a greater peak and germination value than small seeds, indicating greater vigor and a more rapid germination rate thus more uniform seedlings. Seedlings from large seeds, as indicated by fresh and dry weights, were larger and contained a greater leaf area than those produced by small seed.

Sweet corn (Zea mays var. rugosa L.) seed with the endosperm mutant shrunken-2 (sh2) often exhibit low seed vigor and poor field emergence. Seed respiration and carbohydrate metabolism during germination of supersweet `Jubilee' (sh2) and sugary sweet `Jubilee' (Sh2) were studied. There were no significant vigor differences expressed by isolated embryos from sh2 and sugary (Sh2) seeds, indicating similar embryo physiology. Respiration rates were higher in the sh2 genotype during early stages of germination (24 hours) while they declined later. The available sucrose originating from the endosperm reserves was depleted by day 4. This insufficiency of a sustained energy source due to rapid consumption and minimal stored reserves may limit subsequent seedling growth in the sh2 genotype.

Optimization of crop production can be accomplished only if successful stand establishment is achieved first, since each plant contributes to the total crop yield. Reduction of plant populations after planting will reduce yield and/or quality, even though plants compensate to some degree for stand losses. Successful stand establishment is achieved if factors that affect establishment are known, evaluated, and modified appropriately at the time of field planting. The factors that affect stand establishment are biotic and/or abiotic. Biotic factors are generally pathogens that attack plants as parasites, while abiotic factors are the environmental and physical conditions to which the plant or seed is exposed at the time of planting. Abiotic factors can be classified under three headings: soil, planting requirements, and environmental stress.

Highly educated and demanding customers, complex business structures, rapidly changing technology, greater liability, and strong competition bring unprecedented pressures on the vegetable seed industry. An effective quality system involving all of the business functions (breeding, parent seed maintenance, production, processing, testing, seed treatment, packaging, marketing, and customer service) seems to be inevitable. The future of the seed business belongs to companies that can provide continuous supplies of high-quality seed with necessary support and technical services and can afford investment in a rapidly advancing technology.

The cause for the differences in germination ability of large and small confection sunflower (Helianthus annuus L.) seeds was investigated over 3 years. The source-sink relationship was manipulated to better explore the differences between seeds of various sizes and to study the role of the embryo and the pericarp (hull) in controlling germination ability. Percent germination of large seeds was significantly lower than that of small seeds when tests were performed at 15 °C. Increasing the ratio of leaf area to number of developing seeds caused an increase in mean seed mass, but resulted in a lower percentage of germination. Seed vigor, as measured by mean time to germination or to emergence of hulled seeds or by rate of root elongation, was negatively correlated with embryo mass, indicating that the low vigor of large seeds is not due to the mechanical barrier imposed by the hull. Analysis of electrolyte leakage confirmed the hypothesis that the low quality of large seeds results from a disturbance during the process of seed development.

Abstract

Berry weight was correlated with the total weight of true potato seed (TPS) per berry and with the number of TPS per berry. 100-TPS weight was weakly correlated with berry weight and with TPS weight per berry. A negative correlation was found between 100-TPS weight and the number of TPS/berry. The degree of negative association between 100-TPS weight and TPS number per berry increased substantially as berry weight decreased in four of the five progenies investigated. Mean 100-TPS weights from large and from small berries were not significantly different for all progenies. Since seed weight is considered the measure of TPS sowing value, it is suggested that culling small berries is not an appropriate method to improve the quality of a given TPS lot.

Abstract

Field studies were conducted in 1985 and 1986 to evaluate the effects of final irrigation timing on spring pea (Pisum sativum L. cv. Mars) seed yield, percent germination, and distribution of yield within the canopy. Final irrigations were applied on 10 dates during the period from 10% bloom to early senescence. Total seed yield did not increase with irrigations applied past 237 degree-days (base 4.5°C) after bloom (DDAB) in 1985 or 366 DDAB in 1986. However, the highest germination percentages and viable seed yields in 1985 and 1986 were obtained when final irrigations were applied at 487 and 450 DDAB, respectively. In 1986, total seed yield, percent germination, and viable seed yield throughout the canopy increased when the final irrigation was applied at 366 or 588 DDAB compared to earlier final irrigations. Viable seed yield reductions for the early irrigation cut-off dates resulted primarily from reduced numbers of pods per plant, and seeds per pod in the upper canopy (nodes 14 to 17) and decreased germination of seed produced throughout the canopy. We conclude that application of the final irrigation at ≈450 to 500 DDAB (usually 2 weeks after final pod set) should produce viable seed yields similar to those obtained with continued irrigation through early senescence.

This study examined the use of random amplified polymorphic DNA (RAPD) markers as a means to identify cultivars of petunia (Petunia hybrida Vilm) seedlings and cyclamen (Cyclamen persicum Mill.) seeds and to determine the genetic purity within cyclamen seeds. Bulked samples of six petunia and five cyclamen hybrid cultivars, respectively, produced consistent RAPD marker profiles. Evaluation of individual seeds from a single cyclamen hybrid produced polymorphic banding patterns that were attributed to genetic variability present in the female and male inbred parents. These results show that RAPD makers can be used to quickly assess the genetic purity of selected cultivars of these two flower seed crops.

Abstract

Isogenic white-seeded (WS) lines of common bean (Phaseolus vulgaris L.) were developed from colored seeded (CS) lines by backcrossing and mutagenesis. Each CS line was selected for its specific resistance to Pythium, Fusarium, Rhizoctonia, seed corn maggot, mechanical damage, or cold tolerance. In all instances, the WS lines, with the p gene, were inferior to the CS lines with P.