Two large-insert soybean genomic libraries constructed in a binary vector:applications in chromosome walking and genome wide physical mapping

Large DNA insert libraries in binary T-DNA vectors can assist in the isolat ion of the gene(s) underlying a quantitative trait locus (QTL). Binary vect ors facilitate the transfer of large-insert DNA fragments containing a QTL from E. coli to Agrobacterium sp. and then to plants. We constructed two so ybean large-insert libraries from cv. Forrest in the pCLD04541 (V41) binary vector after partial digestion of genomic high-molecular-weight DNA with B amHI or HindIII. The libraries contain 76,800 clones with an average insert size of 125 kb, and therefore represent 9.5-fold haploid genome equivalent s. Colony hybridization using a chloroplast-specific probe infers that the libraries contain less than 0.5% clones of chloroplast DNA origin. These tw o libraries have provided clones for physical mapping of the soybean genome and for isolation of a number of disease resistance genes. One microsatell ite marker was identified from the clone that hybridized to the Bng122 RFLP probe. The sequence-tagged site was used for genetic mapping and marker-as sisted selection for genes underlying resistance to the soybean cyst nemato de and sudden death syndrome.