Authors
Choaa A.
El Mohtar
,
Hagop S.
Atamian
,
Rachel B.
Dagher
, and
Yusuf
Abou-Jawdah
,
Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon
; and
Melinda S.
Salus
and
Douglas P.
Maxwell
,
Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706
ABSTRACT
Fusarium vascular wilt, caused by Fusarium oxysporum f. sp. lycopersici, affects tomatoes worldwide. Development of resistant varieties of tomato would constitute an economically and environmentally sound approach for the management of this disease. Resistance genes to F. oxysporum f. sp. lycopersici race 1 (I-1 gene) and race 2 (I-2 gene) were mapped to chromosome 11. The I-2 gene cluster includes one functional copy and six nonfunctional homologs of the I-2 gene. This report describes the design of primers based on the functional gene copy and the development of a multiplex polymerase chain reaction (PCR)-based method that has the ability to differentiate I-2 genotypes from genotypes without the I-2 gene. In these trials, 39 of the 40 genotypes tested with known reactions to race 2 gave the expected results. The only exception was the cultivar Plum Crimson carrying the I-3 gene for resistance, which confers resistance to F. oxysporum f. sp. lycopersici races 1, 2, and 3. This method was validated in three countries and by bioassays.
