Geographic variation of esterase and malate dehydrogenase allozymes in two spider mite species, Panonychus osmanthi and P. citri (Acari: Tetranychidae) in Japan

Abstract

The genetic basis of malate dehydrogenase (MDH) and an esterase (α-Est 3) in the citrus red mite Panonychus citri (McGregor) and P. osmanthi Ehara and Gotoh was studied by polyacrylamide gel electrophoresis and crossing experiments. Based on the banding patterns and the phenotype-segregation ratio, the MDH-1 appeared as a dimeric enzyme of a single locus composed of three codominant alleles (S, M and F) in P. citri. Esterase (α-Est 3), also a dimeric enzyme regulated by two codominant alleles (S and F), was polymorphic in some populations of P. citri, and the frequency of the F allele was higher in southwestern populations than in other populations. The F allele of P. osmanthi, a mite that superficially resembles P. citri, was observed in only one population and all others were fixed for the S allele. At the MDH-1 locus, all populations of P. osmanthi and P. citri were fixed for the M allele with one exceptional population of P. citri. In this population, most females exhibited a single band of the ‘MM’ homozygote, but one female showed three bands of the ‘SM’ heterozygote and two females showed three bands of the ‘MF’ heterozygote. Thus, little geographical variation was found in allele distribution at the MDH-1 locus, but some variation was detected at the α-Est 3 locus only in P. citri.