GENERATION OF SIRRL GENETIC MARKERS FOR EUROPEAN CORN BORER, WESTERN BEAN CUTWORM, AND A TORTRICID PEST OF PRAIRIE CORD GRASS
Location: Corn Insects and Crop Genetics Research
Project Number: 3625-22000-017-01
Specific Cooperative Agreement
Start Date: Jan 06, 2011
End Date: Feb 28, 2014
Objective 1: Confirm and demonstrate the utility of Sequencing Individuals in Reduced Representation Libraries (SIRRL) as a tool for linkage mapping and population studies of the European corn borer, Ostrinia nubilalis, a major lepidopteran pest of agriculture. Objective 2: Verify that SIRRL can be used to generate markers for non-model lepidopteran species, which are increasing in pest status (western bean cutworm, Striacosta albicosta) or may become a significant new pest (prairie cordgrass caterpillar, Tortricidae).
Up to 50 barcode-tagged "A" adaptors bearing HindIII overhangs will be designed for Illumina sequencing chemistry. Up to 50 European corn borer (ECB) siblings will be used to prepare a SIRRL sample, each bearing an adaptor with a different barcode. Individual DNA samples will be pooled prior to size selection. The SIRRL sample will then be prepared according to the optimized conditions and sequenced using one of the two regions of a PicoTiter plate. Software and published algorithms will be used to determine the reads that derive from each individual, based on the barcodes. Barcode sequences will be masked prior to using the newbler software to group reads into genomic regions. The association between grouped reads and individual insects will be used to determine individual genotypes. To verify repeatability of the SIRRL method, the experiment will be repeated in its entirety using the same set of DNA samples and the results compared.
The suitability of SIRRL markers for the construction of linkage maps will be demonstrated using two F1 families of ECB. A sample of 50 individuals per family will be labelled with 50 barcoded SIRRL adaptors and each sequenced on one region of a PicoTiter plate (i.e., one full instrument run per family). The genotypes of each individual will be determined using the methods developed in the experiments described above, and linkage relationships between polymorphisms established.
The SIRRL method also will be applied to samples of approximately 200 ECB collected from field populations in IA and PA. Batches of up to 50 individuals will be prepared, each labeled with a different barcoded adaptor. Each batch will be sequenced using one region of a PicoTiter plate (i.e., a total of two instrument runs). The genotypes of each individual will be determined at each polymorphic site identified. The genetic variation revealed by SIRRL can be analyzed like that from any other co-dominant genetic marker. Basic population genetic analyses, such as tests for departures from Hardy-Weinberg genotypic proportions and allele frequency differences between locations will be conducted to evaluate the utility of SIRRL in population studies.
We will test the ease with which SIRRL can be applied to species with little or no prior genetic characterization. We will apply SIRRL to samples of up to 100 individuals of two such species, the western bean cutworm and the prairie cordgrass caterpillar. Initially, 50 individuals from each species will be labeled with barcoded adaptors and the sample from each will be sequenced on one region of a PicoTiter plate (i.e., one full instrument run for both species). The data from this first run may indicate that modifications to the sample preparation are needed (e.g., a narrower or broader size selection). If so, these adjustments will be made and the experiment repeated using the same samples. If the results of the first experiment indicate that no modifications are needed, an additional 50 individuals from different populations from each species will be examined, and the degree of genetic divergence between populations will be examined.