3.4 │ Catalase activity (CAT)
The changes in CAT activity of the six cucumber genotypes after
inoculation with P. melonis are shown in Table 2 and 5 and Fig 4.
Before inoculation, the CAT activities in resistant and moderately
resistant genotypes (Soheil and Baby), were significantly higher than
another resistant genotype (Ramezz) (Table 5). After inoculation, the
CAT activity in Soheil increased sharply to 20.3 U mg−1 at 14 DAI and
then decreased at 21 DAI (Fig 4. A). A similar pattern was also observed
in Ramezz. However, the CAT activity in another moderately resistant
genotype (Baby) showed a different reaction, with a non-significant
decrease after inoculation at 14 DAI and a significant increase at 21
DAI. The maximum amount of CAT activity in roots of inoculated plants
was observed in Ramezz and Soheil (Table 5). No significant difference
was found in two susceptible genotypes, Extrem and Mini 6-23 (Table 5
and Fig 4.D and E). In another susceptible genotype (Yalda) CAT activity
never exceeded the activity before inoculation at 14 and 21 DAI (Fig 4.
F). However, no correlation was observed between damping-off
susceptibility and CAT activity changes (Supplemental Table 1).