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Poster: Biology & Disease Mgmt: Mycology


Greenhouse Evaluation of Dosage Responses of the Tomato I3 Gene to Fusarium oxysporum f. sp. lycopersici race 3.
C. LAND (1), C. Land (2), G. Vallad (2), S. Hutton (2), R. Willis (2) (1) University of Florida, U.S.A.; (2) University of Florida, U.S.A.

Fusarium oxysporum f. sp. lycopersici (FOL) causes an aggressive vascular wilt disease on tomato. The goal of this study was to evaluate increasing soil levels of FOL on tomato plants with and without the I3 gene conferring resistance to race 3 FOL isolates. Soil inoculum of a race 3 FOL isolate was produced in a corn meal:sand medium and diluted with a pasteurized field soil to levels of 104 to 101 cfu/g soil. Tomato seedlings with and without the I3 gene were transplanted to pots filled with 6 levels of infested soil, including a non-infested soil, and periodically evaluated for plant height and disease severity over 2 months. Afterwards, plants were uprooted, shoot fresh weights were measured, and roots and hypocotyls were plated onto Komada’s medium. A significant difference in total biomass was observed between I3 homozygous and heterozygous plants, with I3 homozygous plants exhibiting 20% greater growth compared to susceptible plants regardless of the initial level of soil inoculum. Plants grown in non-infested soils were symptomless, exhibiting either undetectable or very low levels of FOL recovery from the hypocotyls. Heterozygous I3 plants grown in 10 cfu/g of FOL infested soil exhibited 70% hypocotyl infection, which was the highest rate of vascular infection of all treatments.