Maize Weevil
Overview
The maize weevil, Sitophilus zeamais, is a worldwide pest in stored grains, including in Mexico. Control methods for this species have largely focused on breeding resistant maize landraces, insecticides, essential oils, and hermetic storage techniques. Genetically engineered maize containing Bacillus thuringiensis (Bt) toxins are not effective at controlling this species as Bt-maize targets Lepidopteran pests. Although the maize weevil is assumed to be a major destructive pest, perceived and actual impacts of maize weevil damage in Mexico remain unclear. Prior to this preliminary study there were no quantitative studies assessing the socioeconomic impact of the maize weevil in Mexico.
Population Structure of Maize Weevil in Southern and Coastal Mexico
I was lucky enough to travel to Mexico for three weeks as part of a training class related to my IGERT fellowship. We spent one week in Mexico City and at the International Maize and Wheat Improvement Center (CIMMYT) in Texcoco learning from diverse groups interested in maize in Mexico. We then traveled to Yanhuitlán in the state of Oaxaca to work with subsistence farmers. There, we observed that the most common pest of stored maize was the maize weevil, but that farmers had varying levels of concern about the damage they cause. Mike S. Jones, a graduate student in Economics, and I wanted to explore this phenomenon further. Therefore, we wrote a proposal and were granted funds from the Genetic Engineering & Society Center at NC State University to return to Mexico to conduct an interdisciplinary study to assess the bio-economic landscape of maize weevil in coastal and southern Mexico.
In this project we aimed to 1) determine environmental and cultural drivers of grain damage by the maize weevil, 2) discern perceived and actual impacts of maize weevil on rural farm households, and 3) measure the genetic differentiation of wild-caught maize weevils from multiple communities in Oaxaca and Chiapas, Mexico.
View the paper we published on the population genetic structure of this species in PLoS One.
Photos from field work in beautiful Oaxaca and Chiapas, Mexico.
The First High-Density Linkage Map for Sitophilus zeamais
As genetic pest control techniques evolve it is important to identify species that may one day benefit from these advances. The maize weevil may be an agricultural pest species targeted for control by these technologies due to its threat to the food security of subsistence farmers. However, before any laboratory advancements can be made, genomic tools need to be developed for the species. Despite the widespread presence of and damage that this pest causes very few genomic resources exist. I tried to ameliorate this problem by creating the first linkage map for this species. A linkage map can aid in QTL mapping, genome-wide association studies, and future genome assembly of this species. To make the map I created and F2 cross between two laboratory strains of maize weevil and used the ddradseq technique to identify polymorphic loci in the species. I then applied traditional mapping techniques to order the markers into 11 linkage groups that correspond to the 11 autosomes that this species carries.
Linkage Map
Each linkage group is represented by a black bar and is numbered at the top. The distance (cM) for each linkage group is listed at the bottom and each marker is represented by a tick mark to the right side of the linkage groups.
View the paper we published on the linkage map for this species in Peer J.