Allelism of Cf-12 and Cf-21

Laterrot, H. and Moretti, A. Station d'Amelioration des Plantes Maraicheres, Domaine Saint-Maurice, 84140 Montfavet, FRANCE

More than a hundred isolates of Fulvia fulva (= Cladosporium fulvum) were inoculated on a series of resistant lines in order to study the stability of their resistance. Two lines received from E.A. Kerr in 1980 showed a highly similar reaction: a partial resistance which, after artificial inoculation generally takes the form of white areas composed of mycelium with sometimes a very weak sporulation. The lines concerned are Ontario 798 (Cf-12) and Ontario 7811 (Cf-21).

Because we suspected that an allelic relationship existed we carried out an allelism teat. The results of which are given in Table 1. The test was carried out using a Cladosporium isolate belonging to race 0 and which was isolated in 1986 from open field grown tomatoes at Sarrians, in South-East France. This isolate is highly sporulant. Three pairs of Ontario 798 and Ontario 7811 plants served as the basis of the test which can thus be considered as covering 3 repetitions.

Not one susceptible plant was found among the 139 F2 plants (ONT 798 x ONT 7811). Thus the allelism of Cf-12 and Cf-21 can be concluded. The allelism of Cf- 21 with Cf-16 being demonstrated in a precedent test (Laterrot and Moretti, TGC Report No. 39, 1989, p 22-23) it can be considered until there is proof to the contrary that Cf-16 and Cf-21 are two reoccurrences of Cf-12.

Table 1: Response of plant populations and lines after inoculation with a race 0 Cladosporium isolate

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Populations or lines                           Number of plants by class
                               ________________________________________________
                                 I      B       BS     S     SS    SSS    TOTAL
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F1 (ONT 798 x ONT 7811) 1       12      8        -     -      -      -     20
F1 (ONT 798 x ONT 7811) 2        2     15        -     -      -      -     17
F1 (ONT 798 x ONT 7811) 3        -     20        1     -      -      -     21 

F2 (ONT 798 x ONT 7811) 1       23     22        -     -      -      -     45 
F2 (ONT 798 x ONT 7811) 2        8     40        -     -      -      -     48
F2 (ONT 798 x ONT 7811) 3       22     24        -     -      -      -     46

ONTARIO 798 (Cf-12)              -     14        1     -      -      -     15
ONTARIO 7811 (Cf-21)             1     16        -     -      -      -     17
Monalbo (susceptible line)       -      -        -     2     14      3     19
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Class of attack:        I: no symptoms
                        B: white specks with abundant mycelium
                        BS: the same as B plus some sporulation
                        S: moderate sporulation
                        SS: heavy sporulation
                        SSS: very heavy sporulation