Pollination is the process on which plants depend to transfer pollen grains from anther to stigma. It can be either cross-pollination or self-pollination, and their results vary. All pollinations will not lead to a successful fertilization because of a successful fertilization pistil of a flower has to recognize its right pollen of same species. In other words, pollen and stigma should be compatible. Incompatibility may lead to rejection of pollen. This situation is undesirable, especially in commercial crop production. Thus, artificial hybridization was developed.
As mentioned, pollen-stigma compatibility is essential for a successful pollination and fertilization. Once compatible pollen is accepted by pistil, events for fertilization proceeds, whereas incompatible pollen will be rejected. This interaction where a pistil is capable of recognizing its pollen is the result of long-term pollen-pistil interaction and chemicals released by pollen.
Understanding of pollen-pistil interaction is important in hybridization. It is one of the innovative methods of the crop production improvement program. During artificial hybridization, only the desired pollen grains are introduced to the stigma through pollination. This helps to avoid unwanted pollen rejection and saves time.
Hybridization proceeds in two steps, one is emasculation and another is bagging.
Emasculation: We know hybridization is the method of selective breeding. Thus, anthers have to be removed from a bisexual flower before they release pollen grains. This step of removal of anther using forceps is termed as emasculation. In the case of unisexual flowers, this step is not necessary.
Bagging: Bagging is the protection of emasculated flower from contamination by undesirable pollen grains. Here the flower is masked by a bag, still, the flower attains receptivity. In unisexual flowers, bagging is done before the flowers are open.
Emasculation and bagging ensure that female flower is completely protected from contamination.
Once the flower attains stigma receptivity, the desired pollens are dusted on the stigma. This is resealed for further developments. Hence, artificial hybridization ensures that right type of pollen has transferred to the stigma of the flower. In addition, the chance of fertilization is high. Through this approach, a variety of strains of crops can be developed and it improves the quality of crop with desirable characters.
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