Recent Advances in Genetics and Genetic Improvement of the Phytoseiidae

Abstract

Before 1950, biological information on predatory mites in the family Phy­ toseiidae (Acari: Gamasida) was limited, and fewer than 20 species had been described taxonomically (57, 72-74). However, widespread use of synthetic organic pesticides after World War II resulted in worldwide outbreaks of spider mites. Biological and ecological studies during the 1 950s and 1 960s indicated that phytoseiids could be the premier biological control agents of spider mites in greenhouses, deciduous orchards, vineyards, and citrus (26, 57-58, 74, 101). Taxonomic information also expanded; there are approximately 1000 species known today (40). However, genetic studies of the Phytoseiidae were sparse until recently and generally restricted to cytological investigations (39, 74). Since 1972, knowledge of the fundamental genetics of phytoseiids has accumulated and several species have been the subjects of genetic improvement programs. This paper reviews what is known about their cytogenetics, sex determination, sex ratio, intraspecific variability, reproductive incompatibil­ ity, responses to inbreeding, and artificial selection. Genetic improvement projects involving four phytoseiids are described, and the implementation of strains selected for pesticide resistances and nondiapause is assessed. Although