First Report of Blight Disease on Buxus Caused by Cylindrocladium buxicola in France

Abstract

Cylindrocladium buxicola Henricot causes twig blight on Buxus spp., severe defoliation, and eventually death of plants, especially in young seedlings (1). The disease was first observed in the United Kingdom and New Zealand in the 1990s and recently, the fungus was detected in other European countries (1). In November 2006, box blight symptoms were observed in a Buxus sempervirens nursery located in the South West of France (La Reole). Since then, more diseased samples from other French sites, including forestry areas and ornamental garden nurseries, have been received, indicating that this disease is spreading. Symptomatic twig samples were sent for lab analysis and dark brown spots were observed on the leaves, sometimes coalescing to cover the entire leaf surface, with black streaks on the stems. Fungal fruiting structures were observed directly on the leaf surface and were examined with a stereomicroscope. Microscopic slides were then prepared by gently pressing a clear adhesive tape onto the surface covered by mycelium and spores, which was further stained with lactic acid and methyl blue. Cylindrical, straight, biseptate, hyaline conidia, 53.8 to 75.3 (64.4) × 4.4 to 5.2 (4.6) μm, were observed, sterile hyphae with terminal vesicles ended with a pointed apex, and conidiophores were penicilliate; all of those characters were consistent with C. buxicola (2). To support the diagnosis, fruiting structures were plated on malt agar media supplemented with 100 ppm of chloramphenicol. The pure culture obtained showed a whitish mycelium with a tan brown center that was in line with the original description of C. buxicola (2). DNA was extracted from the pure culture and the internal transcribed spacer (ITS) region was amplified by PCR using the ITS1-ITS4 primer pair (4). Nucleotide sequence was determined and deposited on GenBank (Accession No. JQ743502). BLAST analysis of the sequence showed 100% identity with all currently available C. buxicola ITS sequences, which confirmed our morphological diagnosis. To our knowledge, this is the first report of C. buxicola (teleomorph Calonectria pseudonaviculata) in France. The occurrence of this disease in France worries the nursery industry since losses can sometimes be dramatic as seen in United Kingdom, where the disease is widespread (3). References: (1) B. Henricot. The Plantsman 9:153, 2006. (2) B. Henricot and A. Culham. Mycologia 94:980, 2002. (3) B. Henricot et al. Plant Pathol. 49:805, 2000. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications, 1990.

Boxwood blight: an ongoing threat to ornamental and native boxwood

“…Subsequent reports of boxwood blight document the progressive spread of the disease across Europe and into Asia over a period of 15 years. Boxwood blight appeared in Germany in 2005, Belgium and France in 2006, Spain and Italy in 2008, Croatia in 2009, and the Czech Republic in 2010 (Brand 2005 ; Cech et al 2010 ; Crepel and Inghelbrecht 2003 ; Pintos Varela et al 2009 ; Saracchi et al 2008 ; Šafránková et al 2012 ; Saurat et al 2012 ). The disease was first identified in Asia in the Republic of Georgia in 2010 and Abkhazia in 2011, where it affected native stands of B. colchica (Gasich et al 2013 ; Gorgiladze et al 2011 ).…”

The forgotten Calonectria collection: Pouring old wine into new bags

“…have chiefly been reported only from South America and the Northern Hemisphere, where they are mostly associated with nursery diseases (Lombard et al., 2010c, Vitale et al., 2013), Cylindrocladium black rot of peanut (Bell and Sobers, 1966, Beute and Rowe, 1973, Hollowell et al., 1998) and box blight of Buxus spp. (Henricot et al., 2000, Crepel and Inghelbrecht, 2003, Brand, 2005, Saracchi et al., 2008, Saurat et al., 2012, Mirabolfathy et al., 2013, Gehesquière et al., 2016). …”

Potential Distribution of Invasive Boxwood Blight Pathogen (Calonectriapseudonaviculata) as Predicted by Process-Based and Correlative Models

“…Many areas with Mediterranean climates, including those in southern Europe and the Pacific coast region of the United States, were included in the potential distribution according to a consensus map of CLIMEX and ensemble correlative model predictions, but Cps has a limited presence in these regions to date. In southern Europe, Cps has been reported on B. sempervirens “Suffruticosa” in nurseries or gardens from only a handful of localities in northwestern Spain [ 114 ], southern France [ 115 ], northern Italy [ 116 ], and Croatia [ 117 ]. The pathogen has seemingly had opportunities to invade southern Europe given its rapid expansion throughout other parts of the continent since the early 2000s [ 8 , 20 ].…”