CONSTRUCTION OF A RICE BACTERIAL ARTIFICIAL CHROMOSOME LIBRARY AND IDENTIFICATION OF CLONES LINKED TO THE XA-21 DISEASE RESISTANCE LOCUS

A bacterial artificial chromosome (BAC) library consisting of 11 000 c lones with an average DNA insert size of 125 kb was constructed from r ice nuclear DNA. The BAC clones were stable in E. coli after 100 gener ations of serial growth. Transformation of the BAC clones by electropo ration into E. coli was highly efficient and increased with decreasing size of the DNA inserts. The library was evaluated for the presence o f organellar, repeated, and telomeric sequences. A very low percentage (<0.3%) of the library consisted of chloroplast and mitochondrial clo nes. Eighteen BACs were identified that hybridized with an Arabidopsis telomere repeat. Sixteen BACs hybridized with the AA genome-specific repetitive sequence pOs48. Twelve clones were isolated that hybridized with three DNA markers linked to the Xa-21 disease resistance locus. The results indicate that the BAC system can be used to clone and mani pulate large pieces of plant DNA efficiently.