*2.6. Tolerance Test*

The eggplant CVS studied in the antixenosis and antibiosis tests were also used for the tolerance test. The seeds were planted in a cultivated tray again, and after germination in the two-leaf stage, the seedlings were transferred to plastic pots (20 cm diameter and 14 cm height). When the seedlings reached the four-leaf stage, 10 female adults were positioned on each CV. surrounded with 50 mesh cloths to prevent the entrance of other pests. The nymphs produced on each plant were removed every 24 h. When the number of female adults of aphids was decreased, more aphids were added so their number reached ten again. The experiment was performed with six replications for each cultivar along with the control groups without aphids' contamination. The experiment lasted 14 days under the same conditions [32]. To calculate the dry weight, the seedlings were dried in an oven at 60 ◦C for three days. The plant height from the soil surface and fresh and dry weight of each CV. were measured according to the following Formulas (2)–(4) [34].


control plant× 100

#### *2.7. Resistance Index Calculation*

A plant resistance index (PRI) was used to compare different tested eggplant CVS [35]. The PRI for each CV. was calculated by dividing the value of any categories (antixenosis, antibiosis, and tolerance) by its highest mean in all studied CVS at a replication. The number one represents the lowest value for the considered mechanism in a CV. The mean number of aphids attracted within 5 days for antixenosis (X), the mean intrinsic rate of population increase (rm) of aphids on each CV. for antibiosis (Y), and the reduction rate in each CV. compared to the control groups for tolerance mechanism (Z) were calculated. Therefore, normalized indices for X, Y, and Z values were used to estimate PRI in the following Formula (5):

$$\text{PRI} = 1/\text{XYZ} \tag{5}$$
