Fusarium oxysporum evades I-3-mediated resistance without altering the matching avirulence gene.
I-3-Mediated resistance of tomato against Fusarium wilt disease caused by Fusarium oxysporum f. sp. lycopersici depends on Six1, a protein that is secreted by the fungus during colonization of the xylem. Among natural isolates of F. oxysporum f. sp. lycopersici are several that are virulent on a tomato line carrying only the I-3 resistance gene. However, evasion of I-3-mediated resistance by these isolates is not correlated with mutation of the SIX1 gene. Moreover, the SIX1 gene of an I-3-virulent isolate was shown to be fully functional in that i) the gene product is secreted in xylem sap, ii) deletion leads to a further increase in virulence on the I-3 line as well as reduced virulence on susceptible lines, and iii) the gene confers full avirulence on the I-3 line when transferred to another genetic background. Remarkably, all I-3-virulent isolates were of race 1, suggesting a link between the presence of AVR1 and evasion of I-3-mediated resistance.
Rep
M
M
Plant Pathology, Swammerdam Institute for Life Sciences, University of Amsterdam, P.O. Box 94062, 1090 GB Amsterdam, The Netherlands. m.rep@uva.nl
Meijer
M
M
Houterman
P M
PM
van der Does
H C
HC
Cornelissen
B J C
BJ
D005656:Fungal Proteins / Q000235:genetics; D005670:Fusarium / Q000235:genetics / Q000472:pathogenicity*; D017343:Genes, Plant / Q000502:physiology; D007113:Immunity, Innate / Q000235:genetics; D018551:Solanum lycopersicum / Q000235:genetics* / Q000382:microbiology*; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D014774:Virulence / Q000235:genetics
D005656:Fungal Proteins