Screening pomegranate cultivars for resistance to Phytophthora nicotianae and P. palmivora causing root and collar rot on pomegranate and sensitivity of the pathogen isolates to mefenoxam

Pomegranate (Punica granatum L.) is an important fruit species for both human nutrition and the pharmaceutical industries, and is also an important export product for Türkiye. Pomegranate root and collar rot caused by Phytophthora nicotianae and P. palmivora is the main disease of this crop and the major limiting factor in production in Türkiye. The susceptibility of ten pomegranate cultivars to P. nicotianae and P. palmivora was investigated. One-year-old plants of ten cultivars (Asinar, Fellahyemez, Hicaznar, Katirbasi, BATEM-Hicrannar, BATEM-Esinnar, BATEM-Onurnar, BATEM-Yilmaznar, Izmir-23 and Izmir-1513) were tested using a soil infestation technique. At the end of the experiment, root weights significantly decreased and it was concluded that all cultivars were susceptible to the pathogens. In addition, leaf blight caused by Alternaria alternata, one of the most widespread foliar diseases of pomegranate in Türkiye, was frequently observed on the leaves of the plants inoculated with Phytophthora spp., while there was little disease on the leaves of control plants. This finding confirmed that plants under stress were more susceptible to pathogen infections. All isolates of P. nicotianae and P. palmivora obtained from pomegranate orchards were sensitive to mefenoxam. While EC₅₀ values of P. nicotianae isolates were between 1.774 and 1.918 μg ml^− 1, those of P. palmivora were between 1.895 and 1.944 μg ml^− 1.