Correlation of genetic and physical structure in the region surrounding the I2Fusarium oxysporum resistance locus in tomato |
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| Authors: | Gregorio Segal Matti Sarfatti Mark A Schaffer Naomi Ori Daniel Zamir and Robert Fluhr |
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| Institution: | (1) Department of Plant Genetics, Weizmann Institute of Science, 76100 Rehovot, Israel;(2) Department of Field and Vegetable Crops, The Faculty of Agriculture, The Hebrew University of Jerusalem, 76100 Rehovot, Israel |
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| Abstract: | Summary The dominant gene I
2 confers on tomato (Lycopersicon esculentum) resistance against the fungus Fusarium oxysporum f. sp. lycopersici race 2. A restriction fragment length polymorphism (RFLP) marker, TG105, has recently been found to be tightly linked to I
2. The potential for cloning this gene by a reverse genetics approach prompted us to describe in both genetic and physical detail the region surrounding the I
2 locus on chromosome 11. We have analyzed patterns of segregation of RFLP markers on chromosome 11 and Fusarium resistance in 140 F2 plants from a cross between Fusarium-resistant and susceptible parental lines. Marker TG105 mapped 0.4 centi-Morgan (CM) from I
2. Physical analysis of TG105 and its flanking RFLP markers, TG26 and TG36, by pulsed field gradient gel electrophoresis (PFGE) yielded a restriction map for this region encompassing at least 620 kb of the tomato genome. TG105 and TG26 hybridized to the same 175 kb MluI-NruI restriction fragment. We have therefore linked two genetically distinct RFLP markers. Based on the 4.1 cM distance between them, we have assigned a mean value of 43 kb for each cM recombination distance in the vicinity of I
2. This local ratio between physical and genetic distances is more than 10-fold below the average for the tomato genome. It should therefore be possible to clone I
2 by chromosome walking from TG105. |
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| Keywords: | Tomato Fusarium wilt disease RFLP Pulsed field gel electrophoresis Plant disease resistance |
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