The Genetics of the Cotton Boll Weevil

Four undergraduate students, Amy Crabtree, Laressa Dickey, Valentine Emechete, and Reginald Udouj, Jr., along with Dr. Harold Bancroft and Dr. Bob Jones, adjunct professor from the biology department of Rhodes College in Memphis, have been working with me as a team to look into the genetics of Anthonomus grandis, the cotton boll weevil. The boll weevil is economically important because it has brought about the loss of billions of dollars in cotton in the southeastern United States.

The basic questions we have been attempting to answer are: (1) what genes are present? (2) how do they function in boll weevil populations, and more specifically (3) what is their effect on diapause (dormancy in insects)? The third question resulted from our discovery and description of the inheritance of two esterases: Estf and Ests, which are autosomal codominant alleles. The esterases were separated with polyacrylamide gel electrophoresis from a whole body squash of the boll weevil. Estf was shown to have a low frequency in the weevils maintained in the lab and that do not diapause and high frequency in feral weevils that do undergo diapause. We would like to find the relationship between diapause and the esterases, since controlling diapause would be beneficial in boll weevil control.

We have shown that certain enzymes, particularly esterases, can be demonstrated in boll weevil fecal droppings. With this technique we are now able to determine the esterase genotype of the insect without sacrificing the animal. We have also worked out the technique for culturing the boll weevil in the laboratory in a much easier manner than before. With the new culture techniques, we hope to make single pair matings of the boll weevils to determine more of the basic genetics of the weevil, as has been done with Drosophila.

Laressa Dickey recently demonstrated a new allele from a more eastern population of weevils. We are attempting to isolate this allele and establish inbreeding strains of the various esterase genotypes. Amy Crabtree is examining morphological characters of the weevils and hopes to correlate them to the different esterases. Valentine Emechete is attempting to use cellulose acetate electrophoresis to accelerate and shorten the esterase separation procedure used for determining the genotype of individual weevils. Reginald Udouj, Jr., is investigating the possibility of improving our standard electrophoresis with pulse-field electrophoresis. Recently, Dr. Jones and I presented a paper on some of our findings at the University of Cardiff in Wales. Laressa has presented two papers at regional meetings on our research. Also, Amy, Valentine, and Reginald plan to present papers on the results of their research at the Collegiate Division of the Tennessee Academy of Science.