Identification of DNA Sequences Involved in Host Specificity in the Pathogenesis of Pseudomonas solanacearum Strain T2005. Qing-Sheng Ma. Laboratory of Molecular Genetics, Guangxi Agricultural College, Nanning, China. Mei-Fang Chang, Ji-Liang Tang, Jia-Xun Feng, Miao-Ji Fan, Bin Han, and Tao Liu. Laboratory of Molecular Genetics, Guangxi Agricultural College, Nanning, China.. MPMI 1:169-174. Accepted 29 April 1988. Copyright 1988 The American Phytopathological Society.

Two genomic libraries were constructed in Escherichia coli from DNA of Pseudomonas solanacearum wild-type strains T2003 (pathogenic to potato, but nonpathogenic to peanut) and T2005 (pathogenic to peanut) by using a broad host range vector pLAFR1. Transferring clones from the strain T2003 library into a strain T2005 derivative recipient, followed by plant pathogenicity tests, revealed no presumptive avirulence gene in the nonpathogenic P. solanacearum donor strain. However, transferring clones from the strain T2005 library to a T2003 derivative recipient resulted in the identification of two transconjugants that can cause wilting on peanut, indicating that the host range of the original nonpathogenic (to peanut) strain T2003 can be extended to peanut by introducting two consmid clones from the strain T2005 library. These two cosmid clones were designated pGX1234 and pGX1236, and restriction enzyme mapping showed that they overlapped in a region containing two EcoRI fragments (12.8 and 2.4 kb). The 12.8-kb EcoRI fragment was subcloned into pLAFR1 vector and shown to retain the ability to extend the host range of P. solanacearum transconjugants to peanut when transferred to strain T2003. The evidence presented here shows that at least some genes for host specificity in strain T2005 are carried in the 12.8-kb DNA fragment.