To overcome the sterility of first-generation hybrids, various methods are used, of which two main ones can be distinguished: 1) backcrosses, 2) doubling the number of chromosomes in hybrid plants to obtain allopolyploid.
The use of crossbreeding is based on the fact that female gametes of a hybrid usually have greater vitality than male ones. The use of normal pollen for pollinating a hybrid of one of the parental forms makes it possible to obtain seeds for further work. For the same purpose, hybrids of the first generation can be pollinated with pollen of the third related species, for example: (rye x wheat) x wheat grass; (rye x wheat grass) x wheat; (wheat x wheat grass) x rye.
The most reliable method for overcoming the sterility of interspecific and intergeneric F1 hybrids is to double their number of chromosomes. Since each type of chromosome in amphidiploids obtained in this way is represented by a pair, meiosis proceeds relatively normally with the formation of viable gametes containing one genome of crossed species. Overcoming the incompatibility of different species and the sterility of their hybrids can be facilitated by several other methods, for example, creating favorable conditions during flowering plants, the use of physiologically active substances, chemical mutagens, and other factors.
The number of seed set on hybrid F1 plants also depends on the total number of flowers, which can be increased by creating the most favorable conditions for the formation of generative organs, as well as by vegetative propagation of plants. Quite effective methods have been developed for cloning various plant species, including cereals, such as rice, etc.
The use of new methods of biotechnology significantly expands the possibilities of the practical use of remote hybridization. Among these methods can be attributed the culture of anthers, embryos, and fusion of protoplasts.
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