A Comprehensive Review on Breeding Technologies and Selection Methods of Self-pollinated and Cross-Pollinated Crops

The basis of crop improvement is the existence of genetic variability in plant material. A breeder exploits it in several different ways to create new crops varieties which are capable of outperforming their ancestors in the expression of various economic characters like yield, quality, resistance to diseases, and tolerance towards drought conditions. Breeders obtain their purpose by using different breeding technologies and selection methods. This review categorizes all the breeding technologies into two main portions of selection methods of self-pollinated crops and that of cross-pollinated crops. The principal methods by which new varieties of self-pollinated crops originate are selection and hybridization. Self-pollinated crops can also be developed by pure-line selection methods. Dirk and Penjamo-62 of wheat, IR-6 of rice, and Beechar of barley are the cultivar introductions in Pakistan. Using these methods, most of our crop varieties like wheat, cotton, sugarcane, maize, clover, and several other crops can be originated. The second portion of this review explains breeding methods of cross-pollinated crops. The methods used in the breeding of cross-pollinated crops or crops such as cotton and sorghum which have both self and cross-pollination are not as clearly defined as the methods used in the breeding of self-pollinated crops. In addition, these methods tend to vary with the particular crop with which the breeder is working. Principal methods by which varieties of cross-pollinated crops can be originated by selection and hybridization. The selection method for cross-pollinated crops consists of mass selection, pure line selection, progeny selection, line breeding, and recurrent selection methods. While hybridization includes intervarietal and interspecific crossing and utilization of hybrid vigors. The whole concept gives an amazing figure to the new crop researchers in modern breeding technologies and selection methods.