AFLPs in Pecan Genetics Research
Procedures were refined for extraction and amplification of DNA from pecan [Carya illinoinensis (Wangenh.) K. Koch] leaf tissue. Genomic DNA was extracted from leaf tissue from multiple inventories of `Wichita' and `Pawnee' and processed for Amplified Fragment Length Polymorphism (AFLPs). Using only four AFLP primers, 26 polymorphisms were identified, verifying the reproducibility and consistency of amplification. The application and limitation of the procedure for separating genotypes will be discussed. Twenty-four cultivars and seedlings representing the geographic range of the species were analyzed using 10 primer combinations. Despite the small sample size, polymorphic bands apparently associated with geographic origin were apparent. Individuals from selected controlled-cross families of the Pecan Breeding Program were bulked according to disease reaction and screened using 64 primers. Primary primers were selected on the basis of polymorphisms observed in bulked samples of resistant and susceptible genotypes. Eighteen primer combinations were selected for use on all individuals in the test. The candidate markers were evaluated to verify that parental lines were polymorphic for the trait, reducing to one the number of appropriate primers. That primer was used to screen 84 progeny samples phenotypically rated for disease resistance levels. The data were analyzed for linkage to scab resistance in the population. Factors limiting the utility of AFLPs as tools for selection of disease resistant genotypes, and their use in developing markers for heterodichogamy (a simple dominant genetic system) will also be discussed.