Verticillium wilt is one of the most destructive diseases of eggplant (Sola
num melongena L.). Some researchers have reported that wilt was encouraged
by sufficient soil humidity, while others stated that it was encouraged by
drought. This study investigated the water stress effect on the severity of
Verticillium wilt on eggplant, as it is reflected on yield, agronomic trai
ts and fruit quality. Thus, eggplant seedlings cv. 'Tsakoniki' were transpl
anted in three rows, each with 20 plants, during the summer of 1995 and 199
6 in a plastic greenhouse, at the Agricultural Research Center of Macedonia
and Thrace. Ten of the plants in each row were inoculated with the fungus
Verticillium dahliae, while the other 10 were used as controls. Rows were i
rrigated every 2, 4 or 6 days. Soil humidity was calculated before every ir
rigation in each row. The disease severity was estimated by the disease ind
ex (DI) as the combination product of leaf symptom index (LSI) and vascular
discoloration index (VDI). In addition. the plant height, early and total
commercial yields, fruit numbers of early and total commercial yields, plan
t weight, the above-ground plant weight, root weight, pH, total soluble sol
ids and fruit brilliance plus colour intensity were measured. The effect of
Verticillium wilt on plants irrigated every 2, 4 or 6 days was estimated b
y the correlation coefficient (r) between LSI and DI and the aforementioned
characteristics. Verticillium wilt had a significant but negative effect o
n all of the measured or calculated characteristics. This effect, however,
was independent of the irrigation applied. On average, the early commercial
yield was reduced by 40.8% and the final commercial yield by 39.4%. The on
ly quality characteristic that was affected significantly by irrigation was
the fruit brilliance and colour intensity (r = -0.640 to -0.727, P less th
an or equal to 0.01). Finally, the irrigation frequency (every 2, 4 Or 6 da
ys) had a significant but negative effect on all of the characteristics mea
sured on the control plants. The only exception was fruit quality. In concl
usion, the combined effect of irrigation and Verticillium wilt infection si
gnificantly reduced the early and total production of eggplant and spoiled
the fruit quality.