Research Article
LV D, Zhang JY, Zhang Z, Zh
Abstract
Ten fungal strains that cause apple ring rot disease (Physalospora piricola Nose) were used to study the role of ribosomal DNA-internal transcribed spacer (rDNA-ITS) in classifying and identifying the pathogen Botryosphaeria berengeriana de Not f. sp. piricola (Nose) Koganezawa et Sakuma, and the correlation between sequence mutations and biological characteristics, and pathogenicity. We used an effective method to screen for conidiospore induction in in vitro cultures of the pathologic pathogens. PCR amplification and clone sequencing were performed for the rDNA-ITS region and used to construct a phylogenetic tree. The growth status, sporulation ability, and phylogenetic effect of different strains were determined. The influence of culture medium types, pH, temperature and light, and the effect of mycelia scraping were investigated. Based on the 582-bp and 583-bp cloned fragments, the results show that there are two significant sequence variations in the ITS1 region, and there were variant bases found in the sequences from five strains. All ten strains were shown to be in theâÂ… sub-variety of Botryosphaeria berengeriana f. sp. piricola (Nose) using homology comparisons. The strains with a higher degree of variation performed better in terms of biological characteristics and were more pathogenic than the strains with less variation. The variations in the ITS1 region might have more predictive power. The appropriate developmental conditions for ring rot colonies were determined to be 25-30°C on a potato-based medium at a pH 5.0-7.0. Alternating irradiation of 12 h/d black light and 12 h/d fluorescent light and scrape treatment of fungal mycelia were best able to induce conidiosporangia\r\nand sporulation.