Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/10/2003
Publication Date: 5/1/2003
Citation: Kim, K.S., Sappington, T.W. 2003. DNA fingerprinting boll weevil populations from non-eradicated states and Northeast Mexico. In: Proceedings of the Beltwide Cotton Conferences, January 6-10, 2003, Nashville, TN. 2003 CDROM.
Interpretive Summary: Movement of boll weevils from infested areas into weevil-suppressed areas can slow progress in eradicating this pest of cotton. Reintroductions of weevils can be caused by inadvertant human transport or by natural movement. An increase in trap captures of weevils in an eradication zone may be caused by weevils just arriving or weevils reproducing in the area. Determining where weevils in an eradication zone came from is very important because the appropriate response by action agencies and programs depends on the weevil source. Such information is very difficult to determine. We are developing DNA markers to fingerprint weevil populations across the U.S. Cotton Belt and Northeastern Mexico. Information from these markers has revealed that there is some migration occurring between populations less than 200 km apart. Some populations have unique DNA fingerprints, and this information will help in future determinations of the source of reintroduced weevils.
Technical Abstract: An understanding of boll weevil (Anthonomus grandis, Boheman) dispersal behavior is essential to characterizing and responding to the threat of migration into eradicated zones. Variation in boll weevil mitochondrial DNA (mtDNA) was sampled and analyzed to make inferences on the magnitude and geographic pattern of genetic differentiation among weevil populations. PCR-RFLP analysis was conducted on a large fragment of mtDNA from each of 419 individuals from 20 locations across northeast Mexico and eight U.S. states. A total of 28 distinct mtDNA haplotypes, 17 of which were unique to single locations, were identified from restriction reactions of ten informative endonucleases. The value of within-location haplotype diversity varied from 0 to 0.81, and nucleotide diversity ranged from 0 to 0.36%. Nucleotide sequence divergence among weevil populations ranged from -0.01 to 0.68% with a mean value of 0.13%. Haplotype and nucleotide diversity was generally greater in eastern than western populations, and haplotype frequencies differed greatly in these two regions. Phylogenetic reconstruction of populations revealed two major clades corresponding to eastern and western regions, and is consistent with historical boll weevil range expansion into the southeastern U.S. from Mexico, and a secondary colonization of the High Plains. Evidence suggests that gene flow between eastern and western populations is limited and is intermediate at the regional scale examined.