Burdick, A. B.
At present time there are at least 15 genetical and cytological entities knocking around tomato genetics. These include the 6 chromosomes that Rick and Barton tied to linkage groups (l, 2, 7, 8, 9 and 10). Chromosomes 3 and 6 must include the r c and a linkage groups. In addition, we have chromosomes 4, 5, 11 and 12 upon which no genes have been located. The e and tf linkage groups have not yet been assigned to chromosomes. Over and above this there are numerous new mutations that have not yet received either linkage group or chromosome assigment.
A conclusion arising out of Rick and Barton's original work indicates that three linkage groups, namely r, c and a must be assigned to only two chromosomes, 3 and 6. Neither 3 nor 6 is any good as a trisomic, but we do have a translocation between chromosome 3 and 8 which could serve to identify one of these two chromosomes. I have undertaken the crossing of an r-c-a tester to this translocation and should have results within two years.
The accompanying table indicates a scheme which may be used for associating mutants with specific chromosomal entities. Only two trisomics are necessary in this scheme and these happen to be the two best trisomics from the point of view of transmission. There is no way at present for testing for chromosome 6, but this situation should be remedied as soon as the r, c and a situation has cleared up.
SCHEME FOR SCREENING
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Chromosome 1 2 7 8 9 10 3-6
Linkage Group y d wt al wd H r
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Line No.
Tester 244 wt r
Tester 253 d l u-H
Tester 260 m
Tester 273 y al t
Rick LA 309 Wo^m
T(7-9) 111 x x
T(3-8) 109 x ?
T(5-7) 110 x
T(9-12) 108 x
Triplo-4
Triplo-11
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Chromosome 3-6 3-6 4 5 11 12
Linkage Group c a e tf
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Line No.
Tester 244 c a-hl-j
Tester 253 c
Tester 260 e
Tester 273
Rick LA 309 tf
T(7-9) 111
T(3-8) 109 ? ?
T(5-7) 110 x
T(9-12) 108 x
Triplo-4 x
Triplo-11 x
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