First record of Cylindrocladium pauciramosum on Ceanothus in the UK

Abstract

In August 2002, a sample of Ceanothus was submitted to the Central Science Laboratory by the Plant Health and Seeds Inspectorate with symptoms of wilt and shoot blight. The disease was affecting 10% of 200 containergrown plants at a nursery in East Anglia, eastern England; no recent import connection was found. There were numerous dark brown-to-black diffuse lesions on the stems, with profuse white sporulation on the surface. No sporulation was observed on the leaves, and roots were unaffected.Microscopic examination of the fungus revealed characters typical of the genus Cylindrocladium , primarily due to the presence of a sterile appendage on the conidiophore. Examination of the culture on carnation leaf agar, after 7 days at 25 ° C and 12 h near ultraviolet light, revealed that vesicles were clavate to obpyriform (5-12 m diameter; mean 6·85 µ m) with the widest part below the middle on the majority of occasions (77%). Conidia were hyaline, cylindrical, rounded at both ends, one septate with a range of 44 -58 × 3·5 -4·5 µ m (mean 49·0 × 4·0 µ m). The fungus was identified as Cylindrocladium pauciramosum as described by Schoch et al . (1999). The 5 ′ end of the β -tubulin gene was amplified using primers T1 and Bt2b as described previously (Henricot & Culham, 2002). Comparison of the sequence of the β -tubulin region (accession no. AY880064) with other sequences available in the GenBank database showed it was identical to C. pauciramosum (teleomorph Calonectria pauciramosa ). Koch's postulates were fulfilled by inoculating young plants with a spore suspension (1 × 10 5 conidia mL − 1 ) of the fungus, which was successfully reisolated from the leading edge of infected stems. Control plants did not develop any symptoms. This is the first record of C. pauciramosum in the UK and the first record on Ceanothus . The pathogen has a cosmopolitan distribution and is recorded as affecting other ornamental hosts, but on several occasions has been misidentified as C. scoparium (Schoch et al ., 1999; Henricot & Culham, 2002, Henricot & Beales, 2003 et al ., 1996). In order to analyse the Spanish DED fungal population, 108 isolates were collected from 1992 to 2002 from twigs of DED-affected Ulmus minor trees and stored as described by Brasier (1981). Determination of growth rates at 20 and 33 ° C on malt extract agar, colony morphology, mating type and subspecies were performed as described by Brasier (1981). Reference strains H172, H363 ( O. novo-ulmi ssp. americana ), were used for comparison. Sixteen strains from markedly different isolation origins (La Coruña, Murcia, Navarra or Cáceres) were identified as O. novo-ulmi ssp. novo-ulmi , with a mean in vitro growth rate ( ± SD) of 3·3 ± 1·1 (20 ° C) and 0·0 ± 0·0 mm day − 1 (30 ° C). All the colonies were morphologically typical for O. novo-ulmi ssp. novo-ulmi (powdery and uneven fibrous-striate), and were mating type B. The oldest O. novo-ulmi ssp. novo-ulmi strain was collected in Villadiego, Burgos, in 1994. The identification was checked using RAPD markers (Hoegger ...

Effects of Fungicide Treatments for the Control of Epidemic and Exotic Calonectria Diseases in Italy

“…Effects of fungicides on disease incidence (DI) and mean disease rating (MDR) of leaf spot caused by Calonectria pseudomexicana on bottlebrush under controlled environment conditions" several Calonectria diseases, especially for those caused by C. morganii and C. pauciramosa that represent the majority of disease records reported from ornamental nurseries around the world (2,8,9,15,17,18,20,24,27,28,32,39). Single experiments have previously shown the potential of certain fungicides to reduce incidence and severity of infections caused by C. morganii and C. pauciramosa, well established in Italian nurseries (30,32,39,47), by other more sporadically occurring pathogens, such as C. polizzii (22), and by those exotic in Italian nurseries (C. pseudomexicana, C. tunisiana, and C. Mexicana) recently reported in Tunisia (23).…”