The most cost-effective method for preventing
Phytophthora blight is to use resistant cultivars.
Barksdale et al. (1984) explained
P. capsici resistance with irregular dominance along with modifier genes affected by environmental conditions. Recent studies indicated that resistance to
P. capsici is polygenic (
Thabuis et al., 2003;
Mallard et al., 2013). The polygenic resistance to
P. capsici was examined in four resistance components: receptivity (REC), inducibility (IND), stability (STA) and root rot index (RRI). Receptivity is measured when the pathogen spreads in early infection process 3
rd day of post inoculation (DPI), of the plant. Inducibility means the deceleration of the necrosis length between the 3
rd and the 10
th DPI. Stability is the average speed of necrosis length between the 14
th and the 21
st DPI (
Thabuis et al., 2004a) and the resistant genotypes stop the progressing of disease. Receptivity, inducibility and stability are quantitatively evaluated by the stem inoculation tests on both young and adult plants (
Pochard & Daubèze, 1980) while root rot index is a semi-quantitative criterion useful to determine the resistance of young plantlets (
Thabuis et al., 2004a). Quantitative resistance is more durable than qualitative resistance (
Pilet-Nayel et al., 2017).