Plant Breeding скачать в хорошем качестве

Plant Breeding

Pollen and Pollination Cross-pollination is the process of applying pollen from one flower to the pistils of another flower. Pollination occurs in nature with the help of insects and wind. This process can also be done by hand to produce offspring with desired traits, such as colour or pest resistance. To cross-pollinate a rose plant for example, it is necessary to prepare two different roses that are at a similar stage of development. In general, in contrast to diploid roses which are mostly self-incompatible, tetraploid roses are self-compatible. To prevent self-pollination of the selected seed parent, the anthers (pollen sacs) must be removed from the blooms before any pollen is released. This is best accomplished at sunrise when blooms are in the one-third to one-half open stage. First, all of the petals are removed. This procedure allows better access to the centre of the flower. Next, with tweezers or small scissors, the anthers are removed. If the variety selected as a seed parent will also be used as a pollen parent with other roses, the anthers may be collected in a cup and placed uncovered in a dry place where they will mature and release pollen by the next day. After this operation of emasculation has been performed, the remaining portion of the bud is covered with a white paper bag to prevent unwanted pollen from reaching the stigmas. BREEDING METHODS IN CROP PLANTS. CROSS POLLINATED CROPS N:B While methods for improving self-pollinated species tend to focus on improving individual plants, improving cross-pollinated species, on the other hand, tends to focus on improving a population of plants. A population is a large group of interbreeding individuals. The principles of population genetics are applied to effect changes in the genetic structure of a population. The change is such that only desirable genotypes predominate in the population. In this process of changing gene frequencies, new genotypes will arise. This genetic variability must be maintained so that they can be utilized for further improvements in the future. What Kinds Of Plants Can Be Crossbred? Any two plants of the same genus can usually be cross bred. When breeding plants, growers typically cross two species that are within the same genus. For example, the very famous Ghost Pepper was born of a cross between Capsicum chinense and Capsicum frutescens, two pepper species that are within the same genus, Capsicum. The possibilities are effectively endless. Just take the Orchidaceae family of plants (Orchids). There are over 28,000 accepted varieties of Orchid species and counting. The variety is truly staggering for just one family of plants. So, if you happen to be an adventurous gardener, you may have an interest in crossing two of your own favorite plant varieties. ________________________________________ Plant Breeding vs Genetic Modification You may be wondering whether plant breeding is the same as genetic modification. Well, put simply, no. Plant breeding is the natural selection of ideal plants and crops, while genetic modification involves biological modification at the cellular level. Genetically modified organisms, or GMOs, are always born in a laboratory. That is why they stir up so much controversy, including the argument that you shouldn’t be able to put a patent on life (source). ________________________________________ Is Plant Breeding Safe? Standard plant cross-breeding is a natural process which occurs when pollen transfers from one plant to another. It is a key form of reproduction in many plants and is generally believed to be a safe process in a controlled setting. In mass production crop breeding, precautions are taken to ensure foods are safe to consume. Most plants in the world produce at least some level of harmful ingredients, but in very small amounts. Through breeding it is possible that a new variety will contain higher levels of these substances. There are less natural forms of plant breeding, like mutation breeding, where different forms of light radiation or chemicals are put onto seeds to modify the resulting plants. These methods can be more unpredictable and should be thoroughly researched before attempting. The most important methods of breeding cross-pollinated species are (1) mass selection; (2) development of hybrid varieties; and (3) development of synthetic varieties. Since cross-pollinated species are naturally hybrid (heterozygous) for many traits and lose vigour as they become purebred (homozygous), a goal of each of these breeding methods is to preserve or restore heterozygosity.