|Hirano, Susan - UNIVERSITY OF WISCONSIN|
Submitted to: National American Phytopathology Meetings
Publication Type: Abstract Only
Publication Acceptance Date: August 20, 1997
Publication Date: N/A
Technical Abstract: Quantitative comparisons of the population sizes of two or more bacterial strains in the field are greatly facilitated when each strain is uniquely marked in a way that does not affect its fitness. To construct differentially marked clones of P. syringae pv. syringae strain B728a (a causal agent of bacterial brown spot of bean) for field experiments, we selected the intergenic region between the oppositely transcribed lemA (regulatory gene required for lesion formation) and cysM (cysteine biosynthesis) genes for site-directed insertion of cassettes conferring resistance to either kanamycin, spectinomycin or chloramphenicol. The fitness of B728a clones bearing site-directed insertions in this region was examined on bean plants in the field. At all sampling times, population sizes of the marked clones were not significantly different from the parent. The intergenic region between lemA and cysM in B728a appears to be a null site with respect to field fitness of B728a and thus, a usefu landing site for site-directed single-copy insertion of genes of interest.