Glomerella cingulata on camellia

Abstract

Glomerella cingulata was shown to be associated with a leaf blotch, canker and dieback of imported camellia plants. It was particularly damaging on hybrids of Camellia saluenensis such as C. x williamsii cv. Donation. Pathogenicity tests, using whole plants and detached leaves of cv. Donation, distinguished between virulent and a virulent strains of the fungus. The virulent strain did not cause severe damage when inoculated into a range of other woody ornamentals. Conversely, Colletotrichum spp., including G. cingulata, isolated from other hosts were not virulent to Camellia cv. Donation. Apart from a loss of virulence associated with a mutation to paleness of colonies in culture, virulent isolates with dark‐grey colony centres were morphologically identical to avirulent isolates from camellia, including tea plant (Camellia sinensis), and to some isolates from other hosts. A form of Colletotrichum acutatum isolated from camellia and readily distinguished from G. cingulata by bright pink colonies and conidial shape was shown to be avirulent on Camellia cv. Donation. It is proposed that the virulent form on ornamental camellia be described as Glomerella cingulata f.sp. camelliae.