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ABSTRACT
Growing plant varieties that are resistant to insects is the ideal way to protect the crop against insect losses and at the same time prevent pollution of the environment. Resistance to insects is genetically controlled and expressed as antibiosis, nonpreference, and tolerance. The ability of the insect to attack the plant is also genetically controlled and expresses itself in the form of insect variants called biotypes. Biotypes develop because of selection pressure from resistant varieties and are able to survive, interbreed and develop into epidemic numbers. The genetic interrelationship that exists between the host plant and insect has been studied for some insects and has resulted in a better understanding of how to control insects by resistant varieties. Dynamic plant breeding programs can utilize insect biotypes for locating new sources of resistance, distinguishing between sources of resistance, and determining the inheritance of resistance. In some cases, biotypes having genes that are dominant for avirulence can be systematically released in populations of insects having recessive genes for virulence, resulting in genetic control of the insect after a few generations of release.
Key Words: insect biotypes • resistance to insects in plants • mechanisms of resistance • resistant cultivars
1 Paper presented Aug. 19, 1971, in New York City at the annual meeting of the ASA as part of the symposium "Breeding for Host Plant Resistance to Insects."
2 Research Entomologist, Entomol. Res. Div., Agr. Res. Serv., USDA and the Dep. of Entomol., Purdue Univ., Lafayette, Ind. 47907.
Received for publication December 13, 1971.
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