Fruit trees rust: genus Gymnosporangium pathology spread and host plants of the pathogens

Abstract

Phytopathological examination of orchards of various forms of ownership reveal that every year the rust of pip fruit trees has become widespread and reached its epiphytosis. In 2008, we detected symptoms of rust on pip fruit trees in the form of single yellow spots on pear leaves in orchards of different ages and forms of ownership. The identifcation found that the fungus Gymnosporangium sabinae G. Winter, (1882) (syn. G. fuscum DC. (1805)) was the causative agent of pear rust. The prevalence of pathology was insignifcant within 3–5 %. Every year the percentage of the pathology spread and development had been increasing and in 2021 it amounted to 55-75% and 4-5 points, respectively. Symptoms of the lesion were observed on leaves, young shoots and fruits. Microscopic studies found several species of pathogens of the genus Gymnosporangium, namely G. sabinae G. Winter, G. dobrozrakovae Mitrof., G. confusum Plowr., dominated by G. sabinae G. Winter that in the pathological complex of the affected organs of the pear there are. In 2012, we detected symptoms of rust on apple tree leaves in the form of single yellow spots, with a prevalence of 3 %. The identifcation established that the fungi G. tremelloides Hartig and G. dobrozrakovae Mitrof. were the causative agents of apple leaf rust are with G. tremelloides Hartig having a signifcant dominance. In 2021, the percentage of prevalence and development of this pathology ranged 25–30 % and 2–3 points, respectively. In the collection fund of the Botanical Garden of BNAU the section of Angiosperms is represented by one genus Cydonia Mill and the species C. oblonga Mill. In 2018, we noted a few small spots on the leaves of quince caused by the pathogen G. confusum Plowr. The microscopic analysis of the affected organs of species of the genus Juniperus L. with the signs of rust reveal that the pathological complex involved four pathogens of the genus Gymnosporangium, which are the causative agents of pip fruit trees rust. Seven species of Juniperus L. are ecological niches for rust pathogens of pear, apple and quince, namely Juniperus communis L. – for G. tremelloides Hartig, Juniperus excels – for G. sabinae Wint., G. dobrozrakovae Mitrof., J.foetidissima – G. sabinae Wint. G. dobrozrakovae Mitrof., G. confusum Plowr., J. oxycedrus – for G. sabinae Wint., G. confusum Plowr., J. phoenicea – for G. sabinae Wint., G. confusum Plowr., J. sabina - G. sabinae Wint., J. macropoda – G. confusum Plowr. Кey words: pip fruit trees, rust, agent, Gymnosporangium, Juniperus L.