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Cary L. Rivard and Frank J. Louws

, 12 and 21 July, 9 and 21 Aug., and 5 Sept. Symptomatic plants were identified by unilateral foliar chlorosis and wilting and diagnostic discoloration of the xylem tissue. Fusarium oxysporum f.sp. lycopersici was isolated from symptomatic plants

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Samuel F. Hutton, John W. Scott, and Gary E. Vallad

. Fusarium wilt, caused by the soilborne fungus Fusarium oxysporum f. sp. lycopersici , has been a major disease of tomato in Florida and in other warm production regions worldwide. The fungus colonizes the vascular tissue of plants after infecting the

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J.W. Scott, S.M. Olson, H.H. Bryan, J.A. Bartz, D.N. Maynard, and P.J. Stoffella

`Solar Fire' is a heat-tolerant hybrid tomato (Solanum lycopersicum L. formerly Lycopersicon esculentum Mill.) with resistance to all three races of Fusarium wilt incited by Fusarium oxysporum f. sp. lycopersici Sacc. Snyder & Hansen. It has superior fruit-setting ability in comparison with most existing cultivars under high temperatures (>32 °C day/>21 °C night), and the fruit crack less under the rainy field conditions often present in the early fall Florida production season. Fla. 7776 is the pollen parent in `Solar Fire', providing much of the heat tolerance in this hybrid. It has large fruit-providing breeders with a parent to produce heat-tolerant hybrids with two heat-tolerant parents.

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W. Alan Erb and Randall C. Rowe

Abbreviations: Fol 1 and 2, Fusarium oxysporum f. sp. lycopersici races 1 and 2; Forl, Fusarium oxysporum f. sp. radicis-lycopersici; Mel, Meloidogyne incognita; TMV, tobacco mosaic virus; Verd, Verticillium dahliae. 1 Assistant Professor

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John W. Scott*, Hesham A. Agrama, and John P. Jones

Tomato (Lycopersicon esculentum) line E427 has resistance genes to three races of Fusarium oxysporum f.sp. lycopersici derived from L. pennellii (L.pen) accession LA 716 and L. pimpinellifolium (L.pimp) accession PI 126915. E427 was crossed to susc. Bonny Best and F2 and backcross seed were obtained. Progeny were inoculated separately with Fusarium wilt races 1, 2, or 3. Lines with suspected recombination of resistance were selfed and re-inoculated until disease reactions were homozygous. Four lines were obtained with resistance to both races 2 and 3, but susceptible to race 1. These lines had the L.pen alleles at RFLP markers linked to I-3 on chromosome 7 and lacked L.pimp alleles linked to I and I-2 on chromosome 11. Complementation (F2) data indicated race 2 resistance on chromosome 7 was controlled by a single dominant gene. Three lines were resistant to race 2, but susceptible to races 1 and 3. These lines had L.pimp alleles at TG105 indicating the presence of I-2, and no L.pen alleles at markers linked to I-3. Three lines were resistant to race 1, but susceptible to races 2 and 3. All three had L.pimp alleles at TG523 confirming linkage to I on chromosome 11 and no L.pen alleles at markers tightly linked to I-3. However, one of the lines had L.pen alleles at CT113 on chromosome 7. This and F2 complementation data suggests the possible location of a race 1 resistant locus, I1. Two lines that were Fusarium wilt race 3 resistant and susceptible to race 1 had intermediate resistance to race 2. These two lines did not have the L. pennellii alleles at TG183, TG174, and CT43 near the I-3 locus indicating crossovers in this region reduced race 2 resistance.

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R. Fernández-Muñoz, J. Gragera, M.C. Rodríguez, G. Espárrago, J.A. González, M. Báguena, C.L. Encina, A. Rodríguez, and J. Cuartero

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J.W. Scott, H.A. Agrama, and J.P. Jones

Tomato (Lycopersicon esculentum) line E427 has resistance genes to all three races of Fusarium oxysporum f.sp. lycopersici derived from L. pennellii accession LA 716 and L. pimpinellifolium accession PI 126915. To determine genes that confer resistance to specific races of fusarium wilt, line E427 was crossed to susceptible `Bonny Best' and then F2 and backcross (to `Bonny Best') seed were obtained. Self-pollinations resulted in 337 lines and progeny of each line was inoculated separately with fusarium wilt races 1, 2, or 3. Plants from lines whose segregation suggested recombination of resistance were self-pollinated and reinoculated until disease reactions were homozygous. Four lines were obtained with resistance to both races 2 and 3, but susceptible to race 1. These lines had the L. pennellii alleles at restriction fragment length polymorphism (RFLP) markers linked to I-3 on chromosome 7 and lacked L. pimpinellifolium alleles linked to I and I-2 on chromosome 11. Complementation (F2) data indicated race 2 resistance on chromosome 7 was controlled by a single dominant gene. Three lines were resistant to race 2, but susceptible to races 1 and 3. These lines had L. pimpinellifolium alleles at TG105 and flanking markers encompassing a 14.4 cM region indicating the presence of I-2, and no L. pennellii alleles at markers linked to I-3. Three lines were resistant to race 1, but susceptible to races 2 and 3. All three lines had L. pimpinellifolium alleles at TG523 confirming linkage to I on chromosome 11 and no L. pennellii alleles at markers tightly linked to I-3. However, one of the lines, 415, had L. pennellii alleles at CT113 on chromosome 7. This data along with F2 complementation data suggests the possible existence of a second race 1 resistant locus, I1, in this region. The four lines resistant to both races 2 and 3 were backcrossed again to `Bonny Best' and self-pollinated progeny from 174 plants were screened as described above. Two lines derived from different BC1S1 lines that were fusarium wilt race 3 resistant and susceptible to race 1 had intermediate resistance to race 2. These two lines did not have the L. pennellii alleles at TG183, TG174, and CT43 near the I-3 locus indicating crossovers in this region resulted in reduced race 2 resistance. Collectively, this is the first clear break in the fusarium wilt race 2 and race 1 resistance linkage on chromosome 11. It appears that the race 1 resistance derived from PI 126915 is controlled by the I gene. On chromosome 7, there was a break between the I-3 and I1 genes indicating I-3 does not confer race 1 resistance. The crossovers resulting in reduced resistance to race 2 could be within a complex I-3 locus or a tightly linked race 2 locus.

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Samuel F. Hutton, John W. Scott, and Joshua H. Freeman

); this resistance is conferred by the Sw-5 gene. It also carries resistance to all three races of fusarium wilt incited by Fusarium oxysporum f. sp. lycopersici . Compared with most existing cultivars, Solar Dancer has superior fruit-setting ability