Applying the molecular biology techniques to the detection of Erysiphe alphitoides (Griffon & Maubl.) U. Braun and S. Takam. in plant parts

Erysiphe alphitoides causes the most common disease of assimilation apparatus of oaks of different age. It is believed that the pathogen overwinters in buds of the host plant or in the cracks of the bark. The aim of the study was to search for the presence of E. alphitoides in buds, leaves, and wood of sessile oak shoots using molecular techniques. Two hypotheses have been tested: (i) oaks are infected by E. alphitoides, and (ii) the pathogen overwinters in the host plant buds. The samples used in the study were collected form sessile oak trees (Miradz Forest District; 52°41'23.197'N, 18°25'33.942'E) in 2017, and consisted of dormant buds (collected in May), young leaves (collected in June), leaves with visible symptoms of the disease (collected in August), shoot with sip and surface layers of wood (collected in December). Additional part of buds was collected in May 2018. The PCR reaction was carried out with primers specific for E. alphitoides and E. hypophylla. For species identification Sanger method was used. The resulting sequences were compared using BLAST algorithm with reference sequences deposited in the NCBI database. Sequences from isolates obtained from leaves showed 97−99% similarity to the reference sequence of E. alphitoides. Pathogen did not occur in the superficial layers of shoots and buds. As some studies show, at very low temperatures (below –20°C), the mycelium of the pathogen dies, therefore further study should be undertaken on wintering of the pathogen causing the powdery mildew disease on oaks. It also should be examined whether the pathogen overwinters in the form of bagnial spores produced in chasmothecia overwintering on leaves, in the leaf buds, or in bark cracks, and whether the wintering site of the pathogen is related to the age of trees and or to the stands where the trees grow