Sweet crabapple [Malus coronaria (L.) Mill.], an ornamental treewith a geographic origin in China, has been widely cultivated inKorea as a street or garden tree, because of its beautiful flowers.White rot has occurred since 1990 on the branches, bark, and fruitsof sweet crabapple growing at the campus of Gyeongsang NationalUniversity, Jinju, Korea. Cankers or warts initially appeared asslightly sunken reddish-brown areas on the bark of sweet crabapple.Cankers expanded to 30 cm in length, and branches became weak-ened and eventually died (Fig. 1A). The disease mainly occurred onthe branches, bark, and fruits, but not on the leaves (Fig. 1B −F). Asthe fruits enlarge, a brown decayed area appeared. The decay wasoften characterized by a series of concentric rings, alternating fromblack to brown on the fruit surface (Fig. 1D and E). Eventually, therotted fruits dried out and mummified, sometimes hanging on thetree until the next season (Fig. 1F). Pseudothecia, 50 −120×50−110µm in size, were produced on cankered areas of bark and on mum-mified fruits that had been present on the tree for over a year (Fig.1G). The asci were cylindrical, club- and banana-shaped, and 80 −120×10−12 µm in size (Fig. 1H and I). The ascospores were ovoidand 20 −30×7−12 µm in size (Fig. 1I). Pycnidia, 100 −300×100−350µm in size, produced on the PDA plates under natural light (Fig. 2Aand B). The pycnidiospores were cylindrical oroval and 5 −7×20−30µm (Fig. 2C). For pathogenicity testing, 5-day-old mycelium grownon PDA was artificially inoculated on fruits of sweet crabapple. Thesame fruit rot symptoms were reproduced and the fungus was re-isolated from the symptoms to prove Koch's postulates (Fig. 2D). PCR amplification and sequencing of the complete internaltranscribed spacer (ITS) rDNA was performed using the primersITS1 and ITS4 as described by White et al. (1990). The resulting582-bp sequence has been deposited in GenBank as Accession No.HQ231407. Phylogenetic analysis was performed with MEGA4software using the neighbor-joining method and the Tajima-Neidistance model. The representative isolate showed only one basesubstitution with sequencesfrom Botryosphaera dothidi ea (GQ870285),which infects apple trees (Fig. 3). Mycological measurements,taxonomic characters, pathogenicity, and molecular data coincidedwith those of Botryosphaeria dothidea (Moug.) Ces. & De Not.described by Sutton (1990). To our knowledge, this is the first reportof the presence of B. dothidea on sweet crabapple in Korea (TheKorean Society of Plant Pathology, 2009). The representative cul-ture of B. dothidea BD001 has been deposited at National Academyof Agricultural Science (KACC 45481). Recent occurrence of thedisease suggests that B. dothidea is spreading widely and poses aserious threat to the health of sweet crabapple in Korea.
Search from 250 M+ research papersSearch from 250 M+ research papers
Open Access
Dec 21, 2023
A.A Atamas + 2
