Hybrid seed production

Close coordination between the seed company and the chemical company is essential to assure that yield trials, efficacy trials, hybrid seed production, and the required herbicide label extensions proceed in a concerted fashion. The imidazolinone herbicide must be ready to be used when imidazolinone-resistant corn is ready for sale. Joint launch of the resistant hybrids and the herbicide label extension that includes resistant com will be coordinated by American Cyanamid and Pioneer Hi-Bred. 

Alloplasmlc conversion Is a strategy which emerged from capabilities developed with plant protoplasts. Originally touted as a method for the recovery of exotic Interspecific hybrids (12), protoplast fusion has proven to be an excellent way to approach the wholesale manipulation of mitochondrial genes (13). The predominant trait of note Is cytoplasmic male sterility (cms), which Is of Interest to the seed Industry as a tool to facilitate hybrid seed production. Little or no Impact on possible value-added traits Impacting on food quality, however, Is anticipated from alloplasmlc conversion. 

Hax is a diploid (2n=30) autogamous (primarily self-pollinating) crop plant. Improvement in flax has lagged behind other oilseeds, including canola and soybean, in part because flax occupies a smaller niche as an oilseed and, consequently, received reduced resources for development. Genetic diversity within the crop is low, and cannot be readily supplemented by intraspecific hybridization. Finally, methods of hybrid seed production have not been developed. 

Male sterility is the inability of the plant to produce functional anthers or pollen, through chromosomal aberrations, gene action, or cytoplasmic influences. Plant breeders make use of cytoplasmic male sterility and pollen fertility restorer genes to take advantage of hybrid vigor and superior performance of the hybrid over the parental fines due to heterosis. Many components critical for commercial hybrid production (Palmer et al., 2001) are lacking for flax a stable male-sterile, female-fertile sterility system a selection system to obtain 100% female plants that set seed normally and can be mechanically harvested and an efficient pollen transfer mechanism from pollen parent to female parent. Considerable research is needed before an efficient, productive, and cost-effective system of hybrid seed production conld be available in flax (Green et al., 2008). 

Uncoupling is sometimes important to an organism. The generation of heat by uncoupling is discussed in Box 18-C. The fungus Bipolaris maydis caused a crisis in maize production when it induced pore formation in mitochondrial membranes of a special strain used in production of hybrid seeds.281 282... 

In partial response to his own question, Decker acknowledged the contributions that hybrid seed com, fertilizer, and improved insect control technologies made to com production. He noted that the increased use of insecticides played a role, but he also noted that this unprecedented rise in com yield coincided with the introduction of the triazine... 

Henry A. Wallace developed commercial hybrid seed com (Crabb, 1947), and in 1928 he and Lester Pfister made hybrid pollination completely workable commercially. Eventually, hybrids accounted for nearly all com production in the United States. 

Emasculation of the female parent is used for the production of artificial hybrids. Acid-induced male sterile plants pollinated without emasculation are also used. These hybrids were produced by natural crossing in seed production fields (breeding nursery), with the two parents planted in alternating groups of rows. The first hybrid cultivars were introduced in Canada for commercial production in 1946 (4). 

The production of single crosses or three-way hybrids using cytoplasmic male sterility and nuclear fertility restorer system is widely used. Genic male sterility was used for the production of hybrid seeds in the early 1970s in France and Romania. The first hybrids produced in this way were introduced in the United States in 1972 (4). 

The production of high-quality hybrid seeds does not only depend on the use of parental lines of superior class, but also on the degree of isolation of the cultivation field from other sunflower plantations, including wild varieties. The isolation conditions cannot be accurately established, in view of the role of insects as pollination agent, and the long viability period of pollen yet, recommendations have been made. 

This simple but basic technique has been used to great advantage in the development and production of superior corn hybrids. Even though cytoplasmic male sterility supplanted detasseling for a time, mechanical control of male fertility is currrently the method of choice in hybrid corn seed production (1). ... 

Cytoplasmic Male Sterility. Unfortunately, large-scale mechanical emasculation cannot be applied to all crops of interest. In wheat, for example, the pollen-bearing anthers and female stigmas lay side by side within each floret of a spikelet. Removal of anthers with small, hand-held instruments obviously has utility only for small-scale hybridization experiments. Nevertheless, by crossing a female parent endowed with cytoplasmic male sterility with a male parent that has fertility-restoring genes, one can achieve hybrid wheat seed production. This technology, however, has limitations compared to... 

Lewers, K.S. S.K. St. Martin B.R. Hedges M.P. Widrlechner R.G. Palmer. Hybrid soybean seed production Comparison of three methods. Crop Sci. 1996,36, 1560-1567. 

FIGURE 11.2 Summary of interspecific hybridization experiments for species found in Canada and the United States (see text for references). Solid lines indicate fertile F, hybrids with viable seed production. Dotted lines indicate hybridization occurred, but Fj hybrids could not be obtained without embryo rescue or treatments with colchicine. Arrows indicate the... 

The U.S.D.A. carrot improvement program currently includes approximately 50 inbred carrot lines, and annually tests several hundred hybrid crosses and numerous segregating populations. In addition to culinary and nutritive quality parameters, characteristics being improved include root color, shape, and size, disease resistance, root storage ability, uniformity of flowering, and seed production. All of these characteristics must be maintained at an acceptable level while attempting to improve quality. 

In the selection of plants for creation of complex hybrid population we took into consideration not only competitiveness, but also a group of economically valuable traits yield of overground mass, high seed productivity, resistance to diseases, fodder merits, longevity and winter hardiness. Correlations are calculated between all those traits, and it makes possible to select best genotypes in a short time. 

Synthetic varieties are based on several (more than two) weU-combining parental lines or clones which are grown together in a polycross scheme with open pollination for seed production. The uniformity and performance is not as high as at F, hybrids but the method is simpler and cheaper and the seed quality acceptable for crop production until the second or third generation. Synthetic cultivars are known for chamomile (Franz et al., 1985), arnica (Daniel and Bomme, 1991), marjoram (Franz and Novak, 1997), sage (Aiello et al., 2001), or caraway (Pank et al., 2007). 

Maize is a tall annual grass plant with a strong, solid stem canying large narrow leaves. The male flowers are produced on a tassel at the top of the plant, and the female some distance away on one or more spikes in the axils of the leaves. This separation simplifles the production of hybrid seed. After wind pollination of the filament-like styles (silks), the grain develops in rows on the female spike (cob) to produce the maize ear in its surrounding husk leaves. 

Onset of Product Synthesis in Hybrid Seeds Only... 

---