RESULTS
No monogenic resistance in tested tomato cultivars
The pathogenicity test results with 7 tomato lines against
3 isolates of A. solani showed intermediate resistance
and susceptibility (Table 1). The NCEBR2 and NCEBR4
tomato lines were intermediate resistant and NC84173
tomato cultivar was intermediate susceptible to all 3
isolates of the early blight pathogen respectively (Table
1). None of the tomato cultivars was fully resistant to
early blight isolates because all the tested tomato lines
exhibited variable level of susceptibility from low to high
incidence of necrotic spots on inoculated leaves. The
isolates 5 and 6 of EB were most virulent and less
virulent isolate 2 caused disease on 4, 3 and 2 lines
among tested 7 tomato lines respectively (Table 1).
The results of the pathogenicity tests demonstrated that
LA1392, LA1404 and LA1406 wild tomato accessions
were susceptible to the EB pathogen isolate 5. However,
all the tested wild tomato accessions were resistant to the
isolate 2 (Table 1). The LA1404 was resistant to the
isolate 6, meanwhile LA1392 and LA1406 wild tomato
accessions were susceptible to the same isolate 6 (Table
1).
The final values of area under the disease progress
curve (AUDPC) for the parental lines and established two
F1, F2 and BC1 progenies are presented in Table 2. The
moderately resistant lines NCEBR2, NCEBR4 and
intermediate susceptible NC84173 parents did not exhibit
extreme responses to EB 2 and 5 isolates (Table 2). The
mean AUDPC value for the susceptible parent
(NC84173) was only 1.5 times higher than that for the
resistant parents (NCEBR2 and NCEBR4). Plants of F1
generation were similar to the resistant parents. There
was less variation within for AUDPC range in the F1
generation of NCEBR2 × NC84173 than AUDPC range in
the F1 generation of NC84173 × NCEBR4 (Table 2).
There were statistically significant differences among
the BC1 plants in EB disease resistance, with the AUDPC
values ranging from 2.1 to 27.6 and 7 to 56 for
established populations respectively (Table 2). The
averages of AUDPC values were very similar in both
resistant parents, NCEBR2, NCEBR4 and in their
established BC1 populations (Table 2). It was important
that F1 AUDPC average value was much lower than the
AUDPC of NCEBR2. However, the F1 AUDPC average
value was slightly higher than the AUDPC of NCEBR4