Article
Relationship Between Avirulence Gene (avrA) Diversity in Ralstonia solanacearum and Bacterial Wilt Incidence
Molecular Plant-Microbe Interactions
(2004)
Abstract
Bacterial wilt, caused by Ralstonia solanacearum, is a serious
disease of tobacco in North and South Carolina. In contrast,
the disease rarely occurs on tobacco in Georgia and Florida,
although bacterial wilt is a common problem on tomato. We
investigated whether this difference in disease incidence
could be explained by qualitative characteristics of avirulence
gene avrA in the R. solanacearum population in the
southeastern United States. Sequence analysis established
that wild-type avrA has a 792-bp open reading frame. Polymerase
chain reaction (PCR) amplification of avrA from 139
R. solanacearum strains generated either 792-bp or ≈960-bp
DNA fragments. Strains that elicited a hypersensitive reaction
(HR) on tobacco contained the 792-bp allele, and were
pathogenic on tomato and avirulent on tobacco. All HRnegative
strains generated a ≈960-bp DNA fragment, and
wilted both tomato and tobacco. The DNA sequence of avrA
in six HR-negative strains revealed the presence of one of
two putative miniature inverted-repeat transposable elements
(MITEs): a 152-bp MITE between nucleotides 542
and 543, or a 170-bp MITE between nucleotides 461 and 462
or 574 and 575. Southern analysis suggested that the 170-bp
MITE is unique to strains from the southeastern United
States and the Caribbean. Mutated avrA alleles were present
in strains from 96 and 75% of North and South Carolina
sites, respectively, and only in 13 and 0% of the sites in
Georgia and Florida, respectively. Introduction of the wildtype
allele on a plasmid into four HR-negative strains reduced
their virulence on both tobacco and tomato. Inactivation
of avrA in an HR-positive, avirulent strain, resulted in a
mutant that was weakly virulent on tobacco. Thus, the incidence
of bacterial wilt of tobacco in the southeastern United
States is partially explained by which avrA allele dominates
the local R. solanacearum population.
Keywords
- insertion sequence
Disciplines
Publication Date
2004
DOI
10.1094/MPMI.2004.17.12.1376
Publisher Statement
This is an article from Molecular Plant-Microbe Interactions 17 (2004): 1376, doi:10.1094/MPMI.2004.17.12.1376
Posted with permission. This article is in the public domain and not copyrightable. It may be freely
reprinted with customary crediting of the source.
Citation Information
Alison E. Robertson, W. Patrick Wechter, Timothy P. Denny, Bruce A. Fortnum, et al.. "Relationship Between Avirulence Gene (avrA) Diversity in Ralstonia solanacearum and Bacterial Wilt Incidence" Molecular Plant-Microbe Interactions Vol. 17 Iss. 12 (2004) p. 1376 - 1384 Available at: http://works.bepress.com/alison-robertson/186/