GENETICS OF ENDOSULFAN RESISTANCE IN HYPOTHENEMUS-HAMPEI (COLEOPTERA, SCOLYTIDAE) - IMPLICATIONS FOR MODE OF SEX DETERMINATION

The genetics of endosulfan resistance in Hypothenemus hampei (Ferrari) was studied through classical crosses to determine the degree of dominance anti number of genes involved. After adult beetles were sprayed, mortality was recorded at 6 h and 7 d. Tests of the males from reciprocal F-1 crosses indicated that resistance is sex-linked or that paternal chromosomes are innactive in the sons. Responses of F-1 females after; 6 II indicated degrees of dominance of -0.38 +/- 0.03 anti -0.25 +/- 0.03 for RR X S and SS X R crosses, respectively. In contrast, dominance after 7 d was -0.17 +/- 0.02 and -0.02 +/- 0.02, apparently indicating a trend toward codominance over time. Responses of backcrosses of the F-1 generation to both parental lines and of F-2 progeny were inconsistent with I results predicted when assuming! simple Mendelian inheritance. These results illustrate the practical weaknesses of backcrosses in estimating the number of genes that control resistance irt situations where bioassays are inconsistent or where discrimination between genotypes is poor.