13 RESEARCH NOTES TGC REPORT No . 31, 1981 Table 3 . The growth of pds/pds and VF - 36 plants grown on normal and high nitrogen medium . Germinated seeds were placed in 2 quart jars containing Hoagland's nutrient, 88 mM sucrose and 0 . 9% Difco bacto agar . The jars were placed in a growth chamber and the plants were allowed to grow for 60 days . The values represent the mean weight of the plants in 4 jars . There were 4 plants per jar . Persiel, Friedegunde and R . Reimman - Philipp   Necrosis in tomato produced by the factor for resistance to   Cladosporium fulvum (Cf - 2) and its suppression by Ne . There is some contradiction in the early publications on resistance to Cladosporium fulvum in tomato based according to Langford (Can . J . Res . 15, Sec C . , 108 - 128, 1937) upon a dominant factor for immunity ( Cfp - 1)(later Cf - 2) and in addition to it upon an independently segregating dominant factor for resistance Ne . The latter is told to produce severe necrosis in the resistant plants, but to be expressed only in the absence of the factor for immunity . Therefore, in F 2 from a cross "susceptible x immune" a segregation of 12/16 double dominant = immune : 3/16 dominant only for the factor for resistance = necrotic : 1/16 double recessive = non - necrotic susceptible would be expected . In 1948, Langford (Can . J . Res . 26, Sec . C . , 35 - 64) gave another explanation for the cooperation of the two factors involved in these days in resistance to Cladosporium fulvum . Now, the immunity factor Cfp - 1 (later Cf - 2) was not expected to work independently and epistatically to the factor for resistance Ne, but only together with it in the sense that it suppressed the necrosis produced by the latter . So, in F 2 a segregation of 9/16 double dominant = immune : 3/16 dominant only for the factor for resistance = necrotic 4/16 dominant only for the immunity factor or double recessive = susceptible, non - necrotic would be expected and was shown not only by Langford himself but independently also by Quadt in 1953 (Der Züchter 23, 223 - 243) . While Cf - 2 (formerly Cfp - 1) is located on chromosome 6 L, the necrosis factor is mapped as ne (dominant allelomorph suppressing the necrosis produced by Cf - 2) on chromosome 2 (see TGC 30), although Langford himself in 1948 had mapped Ne on what he believed to be "chromosome I", but what obviously corresponds to chromosome 2 of today . Lyall (TGC 12) found in F 2 from 3 crosses with "Atom" a segregation of 13/16 normal:3/16 necrotic, and suggested