Abstract
Paulownia species are fast growing trees native to China, which are being grown in managed plantings in several European countries for the production of wood and biomasses. In 2018, wilting, stunting, leaf yellowing, and collapse, as a consequence of root and crown rot, were observed in around 40% of trees of a 2-year-old planting of Paulownia elongata × P. fortunei in Calabria (Southern Italy). Two species of Phytophthora were consistently recovered from roots, basal stem bark, and rhizosphere soil of symptomatic trees and were identified as Ph. nicotianae and Ph. palmivora on the basis of both morphological characteristics and phylogenetic analysis of rDNA ITS sequences. Koch’s postulates were fulfilled by reproducing the symptoms on potted paulownia saplings transplanted into infested soil or stem-inoculated by wounding. Both Phytophthora species were pathogenic and caused root rot and stem cankers. Even though P. palmivora was the only species recovered from roots of naturally infected plants, in pathogenicity tests through infested soil P. nicotianae was more virulent. This is the first report of Phytophthora root and crown rot of a Paulownia species in Europe. Strategies to prevent this emerging disease include the use of healthy nursery plants, choice of well-drained soils for new plantations, and proper irrigation management.
Highlights
The genus Paulownia, formerly in the family Scrophulariaceae and regarded as a member of the mono-generic and mono-phyletic family Paulowniaceae according to the Fourth Angiosperm Phylogeny Group (APG IV) classification system, encompasses deciduous hardwood tree species, very probably native to south-eastern China [1,2]
In 2018, There is little on infectious diseases of paulownias and symptomatic most of those necrotic roots, steminformation bark, and rhizosphere soil were sampled from six distinct reported so far are caused by fungi and oomycetes
Fragments of 2 mm were cut from the growing edge of 7-day-old cultures grown in Petri dishes (15 mm diam.) on V8-juice agar (V8A) at 27 ◦ C in the dark, were placed in a 5 cm diameter Petri dish and flooded with non-sterile soil extract water (200 g soil suspended in 1 L of de-ionized water for 24 h at room temperature and filtered)
Summary
The genus Paulownia, formerly in the family Scrophulariaceae and regarded as a member of the mono-generic and mono-phyletic family Paulowniaceae according to the Fourth Angiosperm Phylogeny Group (APG IV) classification system, encompasses deciduous hardwood tree species, very probably native to south-eastern China [1,2]. Paulownia tomentosa, which has a long life and is cold-tolerant, is the most widespread species It behaves as a pioneer species and has been largely used to reclaim disturbed natural, urban, and industrial sites. A single tree can produce around 20 million seeds, which are winged and can be dispersed by wind up to a distance of about 10 km This Paulownia species with its vigorous growth and the shadowing of its large leaves competes with native vegetation and prevents its regeneration [5]. U.S.A. Paulownia elongata and P. fortunei are more thermophilic, very fast-growing tree species, suitable for biomass and wood production in warmer areas of southern Europe, such as Italy and Spain. Paulownia elongata and P. fortunei are more thermophilic, very fast-growing tree species, suitable for biomass and wood production in warmer areas of southern Europe, such as Italy and Spain They seem less invasive than P. tomentosa [5].
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