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 domi nance anti number of genes involved. After adult beetles were sprayed, mortality was recorded at 6 h and 7 d. Tests of the males from recipr ocal F-1 crosses indicated that resistance is sex-linked or that pater nal chromosomes are innactive in the sons. Responses of F-1 females af ter; 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, dom inance after 7 d was -0.17 +/- 0.02 and -0.02 +/- 0.02, apparently ind icating 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 back crosses in estimating the number of genes that control resistance irt situations where bioassays are inconsistent or where discrimination be tween genotypes is poor.