Kerr, E. A. and D. Brewer.
Langford in 1937 identified and determined the linkage relations of three genes--Cf1, Cf2, and Cf3 -- for resistance to leaf mold. Since that time new races of C. fulvum have appeared which thrive on varieties such as Stirling Castle, Vetomold, V-121 and Vulcan. Many accessions of other species and varieties of Lycopersicon are immune from the seven pathogenic races which have been identified. One or more dominant genes for resistance have been isolated from several of these accessions. The commercial varieties Vagabond, Improved Bay State and Waltham Mold-Proof Forcing contain resistance genes from L. hirsutum, L. pimpinellifolium #112215 and L. peruvianum respectively. Still other resistance genes are found in lines which are now undergoing preliminary commercial test.
New dominant genes for resistance (R) to or immunity (I) from race 6 which attacks plants with the genotype Cf1 - Cf2 - Cf3 have been found in the following accessions. Tests for duplication and allelism have not been made.
Accession Source No. of Genes
L. cerasiforme Glecklers 1R
L. hirsutum Alexander 1I and 1R
L. hirsutum var Alexander 1I and 1R
glabratum
L. peruvianum Guba - cross with Prince 2I
Borghese and Pan America
made by Porte and Walker
L. pimpinellifolium Alexander (obtained as 1R
#79532 Missouri #160)
L. pimpinellifolium Alexander 1I and 1R
#112215
Late Blight Resnt Guba 1R
#125
T6-02-M6 and its Andrus 1R
derivative SWST
More resistance genes will probably be isolated from these accessions when
tests are completed. Most of the genes indicated above have been tested for
linkage with the following genes: a, al, br, c, d, dm, e, f, H, j, l, lf, mc,
nc, wt, y. No close linkages have been found using populations of 45 or more
backcross plants. Possible linkage with genes at the extremities of the
linkage groups is now being investigated. It is planned to establish linkage
relations before identifying the various genes with symbols.