Isolation and identification of Phytophthora species on greenhouse cucumber in Southern Kohgiluyeh and oyerahmad province and evaluation of relative resistance of greenhouse cucumber cultivars to them

In order to study the role of Phytophthora species associated with greenhouse cucumber root and crown rot, diseased sampled were collected in Southern Kohgiluyeh and Boyerahmad province. Pieces of infected root and crown of cucumber were washed with tap water blotted dry and plated on CMA supplemented with delvocid (10 ppm pimarcin), ampicillin (250 ppm), rifampicin (10 ppm) and PCNB (150 ppm). 40 isolates recoverd from various parts in Southern Kohgiluyeh and Boyerahmad province. Colonies on the selective medium based on morphological characters produced and temperature requirement, the pathogen were identified as Ph. capsici and Ph. drechsleri. Seventeen isolates were identified as Ph. capsici and 23 isolates were identified as Ph. drechsleri. The reaction of crown and root of 2-week-old greenhouse cucumber cultivars, Mehr, Bahman, Fadia, Close, Negin, Katrina and Cina to virulent isolates of Ph. capsici and Ph. drechsleri was evaluated under greenhouse conditions. The inoculum was obtained on vermiculite-hemp seed extract and positioned around either crown or root systems. Percent dead seedlings and crown and root colonization were evaluated. Comparative percent dead seedlings and crown colonization showed that Mehr and Cina were the most and the least susceptible cultivar in reaction to Ph. drechsleri, also Close and Fadia were the most and the least susceptible cultivar in reaction to Ph. capsici. Comparative percent root colonization showed that Close, Katrina, Mehr and Negin cultivars were not significantly different in reaction to Ph. drechsleri. Cina cultivar was the least susceptible in reaction to Ph. drechsleri, Also Close and Cina cultivars were the most susceptible and Fadia cultivar was the least susceptible in reaction to Ph. capsici.