First Report of Brown Spot Needle Blight on Pinus thunbergii Parl. Caused by Aureobasidium pullulans in China

Pinus thunbergii Parl., known as black pine, is widely distributed all over China. This pine variety can prevent soil desertification and promote soil conservation and is excellent for constructing fast-growing forests and shelter belts. The timber of this species can be used for infrastructure construction and furniture production. In August 2020, needle blight symptoms were found on several trees of black pine in Sichuan Province, China. Further surveys showed that these symptoms are common while the disease incidence is less than 30% which indicated the severity of the disease is mild. The tips of old needles first turn grayish green and developed into brown bands ranging from 1 to 2 mm. To determine the pathogen, 20 needle samples with typical symptoms were disinfected with 75% alcohol, and sections of the tissue were cut from joints of diseased and healthy tissues (visually healthy) with a sterilized scalpel, surface sterilized for 45 seconds in 75% alcohol, soaked for 90 seconds in 1.5% NaCIO, rinsed in sterilized water and dried. Small cut tissues were placed on potato dextrose agar (PDA) at 25℃ for 10 days. Pure cultures were obtained by monosporic isolation. The colonies initially appeared white to cream, yeast-like, and later turned to pink and remained at least 10 days. Conidia were hyaline, smooth-walled, single-celled, and ellipsoidal with variable shape and size, 7.5 to 16 × 3.5 to 7 µm (Zalar et al. 2008). DNA was extracted from the mycelium of the isolate by the cetyltriethylammonium bromide (CTAB) method and amplified through polymerase chain reaction (PCR) with the internal transcribed spacer (ITS) region of rDNA and partial β-tubulin genes of a representative isolate (SC05) were amplified using the ITS1/ITS4 and Bt2a/Bt2b primer pairs, respectively(Wu et al. 2017). The sequences submitted to GenBank (Accession Nos. MW228368 for ITS and MW256762 for β-tubulin) showed high similarity with BLAST sequences of Aureobasidium pullulans (ITS, KR704881 [100%]; β-tubulin, MT671934 [99.49%]). For the pathogenicity test, a conidial suspension was prepared with a concentration of 2.0 × 107 conidia/ml. The suspension was sprayed onto 3 annual seedlings’ needles, and the control was sprayed with sterile water. Inoculated and non-inoculated plants were kept in humid chambers in a glasshouse. After 10 days, typical symptoms appeared on inoculated needles, whereas control needles remained symptomless. The fungus, A. pullulans, was reisolated from those lesions, confirming Koch's postulates. No symptoms were observed on control plants. Aureobasidium pullulans, a ubiquitous saprophytic fungus on many fruits and very rarely reported to cause disease on pine needles. Only reported invasion of Ozone‐injured needles in P. strobus (Costonis and Sinclair 1972) and needles damaged by acid rain in P. sylvestris (Ranta 1990). To our knowledge, this is the first report of brown spot needle blight on P. thunbergii caused by A. pullulans in China. The disease represents a threat to pine manufactures and more research on the pathogenesis and management is needed.

Spread of the invasive pathogen Lecanosticta acicola on species of Pinus in Bulgaria

The brown spot needle blight, caused by the fungal pathogen Lecanosticta acicola, has been the most serious and damaging disease on needles of Pinus spp. in recent years. In Bulgaria, the pathogen was reported for the first time in 2017 in a generative plantation of Pinus sylvestris in the region of the State Forestry Ardino, the Eastern Rhodopes. The newly- established invasive pathogen is considered highly adaptable to new hosts and environmental conditions. The life cycle and symptoms of the disease strongly suggest that the new emerging pathogen has the potential to cause severe damages and is a serious threat to naturally distributed species of Pinus in the country. In the period 2018-2019, a spread of L. acicola from the initial outbreak was established throughout stands of P. sylvestris and P. nigra on the territory of Kardzhali District.

First Report of Brown Spot Needle Blight on Pinus thunbergii Caused by Lecanosticta acicola in Korea

Pinus thunbergii Parl., known as black pine, is a pine native to coastal areas of Japan and Korea. Because of its resistance to pollution and salt, it is planted as windbreakers along the coast. In March 2010, needle blight symptoms were found on several trees of black pine in Naju, southern Korea. Further surveys in 2010 and 2011 showed that these symptoms are rather common but disease incidence is less than 1%. Small, circular grayish green spots first appeared on the needles. The spots developed into brown bands reaching 1 to 2 mm long, sometimes with yellow margins. Dark olivaceous to dark grayish stromata were erumpent and conspicuous on the brown lesions in the later stage of disease development. Conidiophores were simple or occasionally branched, 1- to 2-septate, pale brown to olivaceous brown, and smooth walled. Conidia (n = 30) were olivaceous brown to grayish brown, verrucose, thick-walled, mildly curved, allantoid to fusiform, one- to five-septate (mostly three-septate), and 20 to 45 × 3.5 to 5 μm. Morphological characteristics of the fungus were consistent with those of Lecanosticta acicola (Thüm.) Syd. (anamorph of Mycosphaerella dearnessii M.E. Barr), previously known as the causal agent of brown spot needle blight of pines (2,4). The teleomorph was not observed. On potato dextrose agar, single-spore cultures of three isolates were obtained from conidia sporulating on needles. An isolate was preserved at the Korean Agricultural Culture Collection (Accession No. KACC44982). Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA) and the complete internal transcribed spacer (ITS) region of rDNA was amplified and sequenced with the primers ITS1/ITS4. The resulting ITS sequence of 543 bp was deposited in GenBank (Accession No. JQ245448). A GenBank BLAST search produced an exact match for the sequences of M. dearnessii (= L. acicola) on P. mugo Tura from Lithuania (HM367708) and P. radiata D. Don from France (GU214663), with 100% sequence similarity. To conduct a pathogenicity test, a conidial suspension (approx. 2 × 105 conidia/ml) was prepared by harvesting conidia from 5-week-old cultures of KACC44982 and sprayed onto the needles of five 3-year-old healthy seedlings. Five noninoculated seedlings of the same age served as controls. Inoculated and noninoculated plants were kept in humid chambers for 48 h in a glasshouse. After 28 days, typical leaf spot symptoms started to develop on the needles of inoculated plants. The fungus, L. acicola, was reisolated from those lesions, confirming Koch's postulates. No symptoms were observed on control plants. The disease has been previously reported on several species of Pinus in the Americas (1) and recently in China (3), Japan (4), and Europe (2). To our knowledge, this is the first report of the Lecanosticta-Pinus association in Korea. Occurrence of the disease in Korea is a new threat to the health of black pine, especially in nursery plots. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.arsgrin.gov/fungaldatabases/ December 2011. (2) L. Jankovsky et al. Plant Protect. Sci. 45:16, 2009. (3) C. Li et al. J. Nanjing Inst. For. 1986:11, 1986. (4) Y. Suto and D. Ougi. Mycoscience 39:319, 1998.

Records of Brown spot needle blight related to Lecanosticta acicola in the Czech Republic

There are two records of brown spot needle blight caused by <I>L. acicola</I> in the Czech Republic up to date. Disease was first reported on June 2007 in National Nature Reserve (NNR) Červená Blata, South Bohemia. A more recent discovery of <I>L. acicola</I> took place on August 2008 in the NNR Borkovická Blata. The disease was observed on 10-60 year old <I>Pinus rotundata</I>. Both locations with infected trees are situated inside nature conservation sites under strict protection regimes that are located approximately 50 km apart. In both sites, <I>L. acicola</I> occurred simultaneously with <I>Dothistroma septospora</I>, the red band needle blight causal agent on Scots pine (<I>Pinus sylvestris</I>), bog pine (<I>P. rotundata</I>) and their hybrid (<I>P. × digenea</I>). However, infections of both diseases on the same tree have not yet been observed.

Scirrhia acicola. [Descriptions of Fungi and Bacteria].

A description is provided for Scirrhia acicola[Mycosphaerella dearnessii]. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On pines, including Pinus palustris, P. tueda, P. halepensis, P. nigra (and varieties), P. pinaster, P. pinea, P. sylvestris, P. thunbergii, P. ponderosa, P. strobus, P. monticola, P. attenuata, P. caribaea, P. elliottii, P. radiata, P. echinata, P. glabra, P. rigida, P. serotina, P. sondereggii, P. virginiana. DISEASE: Brown spot needle blight (11, 813; 41, 185). GEOGRAPHICAL DISTRIBUTION: Canada (46, 1929); USA (Southern States, Idaho, Iowa, Kansas, Minnesota, Oregon, Wisconsin); USSR (Republic of Georgia) (46, 3231). (CMI Map 482, ed. 1, 1971). TRANSMISSION: By splash-dispersed, airborne conidia from infected foliage on the tree or after the needles have been cast. The role of ascospores in spread of brown spot needle blight is not known; endospores (45, 3229) have also been described. The incubation period has been found by various authors to be 28-65 days (46, 2329), 2-3 months for young foliage of P. palustris (40, 636) and 4-7 months for old foliage of P. tueda (46, 3230). Accounts of the effect of age of foliage on susceptibility also vary (40, 636; 46, 3230).