Procedure Of Propagation Research Articles

Phenotypic expression of gene OP L for resistance in twospotted spider mites tested with various organophosphates.

The Leverkusen strains of Tetranychus urticae Koch were used for cross-mating experiments, and the phenotypic expression of the main resistance gene OPL reacting with different organophosphates was analyzed. A strain homozygous for this gene was bred in advance of the crossings by a procedure of inbreeding, selection, isolation, and propagation of the RR-genotype. The phenotypic expression of OPL varied according to the toxicant used. Against parathion it was completely dominant (D = 0.995), paraoxon incompletely dominant (D = 0.566), and oxydemetonmethyl and demeton-S-methyl close to intermediate (D = 0.281 and D = 0.204). Monocrotophos showed an incompletely recessive reaction (D = -0.378) and that of CGA 10279 (O-ethyl methylphosphon, odithioate S-ester with 6-chloro-3-(mercaptomethyl) oxazolo[4,5-b]pyridin-2 (3 H)-one) (D = -0.530) was even closer to complete recessivity. A field-resistant population with a high percentage of OPL-heterozygotes would appear to be sensitive toward CGA 10279 and monocrotophos but highly resistant to parathion. In the past, such evidence was occasionally misinterpreted in a sense that a protective mechanism selected by one OP-insecticide was not effective against another one.