J. Pelham (TGC Report 20:37-38) concluded that Tm-1 is located on chromosome 5, close to tf and wt, which are located at positions 40 and 50 respectively (Rick, TGC 30:2-17). Recently, Pitblado (Ph.D. thesis, Univ. of Guelph, Canada, 1983, 70 p) reported that the geno Pto, which controls resistance to Pseudomonas tomato, is also located on chromosome 5 in position 30. He did this using the markers mc and sd situated respectively at positions 0 and 14 (Rick, 1980). We attempted to discover whether a linkage existed between Tm-1 and Pto by studying a series of F3 lines obtained by crossing female "Mobaci" (INRA line, Tm-1) x o "Ontario 7710" (Simcoe Station line, Pto). A total of 88 F3 lines were inoculated at the seedling stage in two separate tests, one using TMV (race 0) and the second using P. tomato. Sixteen plants or more per line were used for each test.
Table 1 gives the results obtained from identification of F2 plant genotypes for Tm-1/2, and Pto. These results indicate that the Tm-1 and Pto loci are independent ( :0.70 > P > 0.50).
Table 1.
Genotypes for Tm-l and Pto of 88 F2 plants(Mobaci xOntario 7710)
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TM-l TM-l +
____ ____ ___
Tm-1 + +
________________ ________________ ________________
Pto Pto + Pto Pto + Pto Pto
___ ___ ___ ___ ___ ___ ___ ___ ___
Pto + + Pto + + Pto + +
________________________________________________________________
Numbers
observed 6 9 8 8 19 8 7 14 9
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Theoretical
numbers^ 1^ 5.5 11.0 5.5 11.0 22.0 11.0 5.5 11.0 5.5
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^1^Assuming independence of Tm-1 and Pto.