DEVELOPMENT OF A SCAR MARKER FOR COMMON BEAN RESISTANCE TO THE BEAN POD WEEVIL (APION GODMANI WAGNER). M.W. Blair', C. Cardona', C. Quintero', R. Garza^ N. Weeden\ S.P. Singh^ / CIAT - International Center for Tropical Agriculture - A. A. 6713, Cali, Colombia, ^/ 3/ EVAMEX, INIFAP - Santa Lucia de Prias, Mexico /University of Montana, Missoula, MT United States / University of Idaho - Kimberly Research and Extension Center - Kimberly ID, United States Introduction: The bean pod weevil (Apion godmani Wagner) is a serious pest of common bean (Phaseolus vulgaris L.) grown in Mexico and Central America that is best controlled by host- plant resistance available in some landraces from the central highlands of Mexico and Guatemala. Yield loss caused by the insect can be as high as 90% but is variable depending on climatic conditions, insect pressure, and cultivars (Cardona and Kornegay, 1999; In Global Plant Genetic Resources for Insect-Resistant Crops). Chemical control of the bean pod weevil uses organophosphate insecticides, which while effective increase production cost and can lead to environmental contamination and health problems. Mechanisms of resistance to the bean pod weevil in common bean are either antibiosis involving a hypersensitive response that encapsulates the oviposition sites, insect eggs or larvae within necrotic tissue; or antixenosis that affects the preference for oviposition sites (Garza et al., 1996; Theor Appl Genet 92: 357-362). Breeding for resistance is effective but hampered by unreliable insect infestation, making the use of marker assisted selection desirable. In the present study, our goal was to develop a segregating population for Apion resistance, test it in the field and use it to develop SCAR markers for molecular assisted breeding. Materials and Methods: The segregating population consisted in 50 Fs:!o recombinant inbred lines derived from the cross Jamapa x J-117, where 'J-117' is a resistance source and 'Jamapa' is a susceptible black-seeded cultivar, both from Mexico. The population was evaluated for Apion resistance over four consecutive seasons (1994-1997) at the Santa Lucia de Prias Experiment Station of the Instituto Nacional de Investigaciones Agropecuarias (INIFAP) near Texcoco, Mexico. All experiments consisted of a randomized complete block design with four replicates. Each test plot consisted of one row, 4 m in length, with spacing of 10 cm between plants within rows and 85 cm between rows. A. godmani was the only major insect pest observed causing damage to bean pods and seeds during the experiments and no pesticides were used during the experiments. The number of damaged and total seeds were recorded, and the percentage of damaged seeds was calculated and data were transformed by the arcsine square root proportion and analyzed using the general linear model (GLM) procedure using the software Statistix. Total genomic DNA was extracted for parents and RILs from three young trifoliolates harvested in 1.5 ml Eppendorf tubes by the method of Afanador et al. (1998; BIC 36:10-11) and used for standard RAPD reactions carried out on a PTC-100 thermocycler from MJ Research with decamer primers from Operon. Bulked segregant analysis was carried out with eight resistant and susceptible genotypes. A single RAPD band (OPK16-890R) was isolated from 1% low melting point agarose gels for ligation into the PGEM-T easy vector from Promega using T4 DNA ligase followed by DNA sequencing of the plasmid and SCAR primer design. 181