First Report of Grovesinia moricola Causing Zonate Leaf Spot on Hernandia nymphaeifolia in Taiwan.

Hernandia nymphaeifolia (C. Presl) Kubitzki, a native tree of Taiwan, is a sea drift plant (Yang and Lu 1996). It is a salt- and wind-tolerant tree (Bezona et al. 2009) and was selected for the afforestation of badlands in coastal areas of Taiwan. In December 2022, all H. nymphaeifolia seedlings at a nursery in Wu-Lai, Taiwan were diseased and wilted with a similar progression. The initial symptom was small zonate white or gray lesions with water-soaked periphery on leaves. Then, expansion and fusion of leaf spots which caused leaf blight and defoliation were observed. Seedlings eventually wilted. Sporophores found on the host were generally hypophyllous, solitary, erect, and easily detachable. The upper portion of the sporophore was considered an individual conidium and consisted of a pyramidal head that was fusiform to ventricose, 206.3 to 501.8 µm (average: 378.0 ± 75.3 µm) long, and 63.6 to 104.5 µm (average: 85.0 ± 16.2 µm) wide at the broadest point (n=30). Branches within the pyramidal head were short, compact, and di- or trichotomously branched. The central stipe was hyaline, broad, septate, tapering toward an acute apex, and sometimes constricted at the basal septum. Sclerotia were gray or black, spherical, and 1.0 to 2.5 mm (n=10) in diameter and observed on older lesions. The fungus was isolated from infected tissue and sporophores and maintained on potato dextrose agar (PDA) at 20°C in darkness. Sclerotia were produced on PDA after 4 to 5 weeks and were irregular or spherical, but no sporophore was developed. The fungus was identified as Grovesinia moricola (I. Hino) Redhead based on morphological characteristics (Tomoko et al. 2006). Three DNA samples was obtained from the cultures isolated from the diseased leaf, sporophores and sclerotia. They were then amplified by PCR with primers for the internal transcribed spacer region (ITS; primers ITS5/ITS4) and the large subunit nuclear ribosomal RNA gene (LSU; primers LR0R/LR5) (Cho et al. 2017), and then sequenced respectively. The sequences were deposited into GenBank with accession nos. PP727191 to PP727193 and PP748518 to PP748520. BLAST analysis of the three isolates showed 100% identity to the sequences of G. moricola from Taiwan (OP550202, OP550203) for the ITS region and 99.9% identity to the sequence of G. moricola from the USA (MW013804) for the LSU rRNA gene. The specimens (FS2022-140) and the culture (Asco-0109) in this study were deposited into the herbarium of Taiwan Forestry Research Institute in Taiwan. Koch's postulates were performed by inoculating four 8-month-old, asymptomatic, potted H. nymphaeifolia plants; every plant was inoculated with sporophores from infected leaves on the upper surface of each of five leaves. Four uninoculated plants were kept in separate pots and served as controls. All plants were covered with transparent plastic bags individually and incubated in a growth chamber at 18 to 20°C with 8 h of light. Similar leaf spots and sporophores were observed after 2 to 4 days and 10 days on every inoculated plant but not on uninoculated plants. The pathogen with a similar colony on PDA was reisolated from the leaf spots of the inoculated plants. Molecular identification of the reisolated pathogen by the above method was carried out. The sequences showed 99.9% identity to the sequence of G. moricola, and were deposited into GenBank with accession nos. PQ157896 to PQ157897 (ITS region) and PQ157701 to PQ157702 (LSU rRNA gene). The pathogenicity test was repeated once. G. moricola is known to cause severe defoliation on woody and annual plants, including at least 73 host species and 36 families distributed in the eastern United States and Japan (Trolinger et al. 1978). This is the first report of G. moricola on H. nymphaeifolia in the world. Control of the disease would play an important role in maintaining healthy seedlings for the afforestation in Taiwan.

Phylogeography of the wide-host range panglobal plant pathogen Phytophthora cinnamomi.

Various hypotheses have been proposed regarding the origin of the plant pathogen Phytophthora cinnamomi. P. cinnamomi is a devastating, highly invasive soilborne pathogen associated with epidemics of agricultural, horticultural and forest plantations and native ecosystems worldwide. We conducted a phylogeographic analysis of populations of this pathogen sampled in Asia, Australia, Europe, southern and northern Africa, South America, and North America. Based on genotyping-by-sequencing, we observed the highest genotypic diversity in Taiwan and Vietnam, followed by Australia and South Africa. Mating type ratios were in equal proportions in Asia as expected for a sexual population. Simulations based on the index of association suggest a partially sexual, semi-clonal mode of reproduction for the Taiwanese and Vietnamese populations while populations outside of Asia are clonal. Ancestral area reconstruction provides new evidence supporting Taiwan as the ancestral area, given our sample, indicating that this region might be near or at the centre of origin for this pathogen as speculated previously. The Australian and South African populations appear to be a secondary centre of diversity following migration from Taiwan or Vietnam. Our work also identified two panglobal, clonal lineages PcG1-A2 and PcG2-A2 of A2 mating type found on all continents. Further surveys of natural forests across Southeast Asia are needed to definitively locate the actual centre of origin of this important plant pathogen.

Ophiodiaporthe cyatheae gen. et sp. nov., a diaporthalean pathogen causing a devastating wilt disease of Cyathea lepifera in Taiwan.

The scaly tree fern, Cyathea lepifera, in Taiwan has been devastated by an ascomycetous pathogen in recent years. This fungus resembles species of Diaporthe, but unlike anamorphs of Diaporthe that produce two types of conidia, its anamorph produces one conidium type. It is described herein as Ophiodiaporthe cyatheae gen. et sp. nov. Through pathogenicity tests, O. cyatheae was demonstrated to be the causal agent of the C. lepifera wilt disease. Of interest, sporulating structures of O. cyatheae have not been found on C. lepifera plants but in culture thus far. The mating system is homothallic. Phylogenetic analyses based on combined sequences of nSSU-rDNA, nLSU-rDNA, EF1-α-1 and RPB2 placed O. cyatheae in Diaporthaceae. Combined sequences of EF1-α-2 and TUB indicated that O. cyatheae had its origin within Diaporthe.

Differences in the Proteomic and Metabolomic Response of Quercus suber and Quercus variabilis During the Early Stages of Phytophthora cinnamomi Infection.

Phytophthora cinnamomi Rands is a cosmopolite pathogen of woody plants which during the last couple of centuries has spread all over the world from its center of origin in Southeast Asia. In contrast to Chinese cork oak (Quercus variabilis Blume) forests native to Asia, which are generally healthy despite the presence of the pathogen, the populations of Cork oaks (Quercus suber L.) in Europe have been severely decimated by P. cinnamomi. The present study aims at identifying the differences in the early proteomic and metabolomic response of these two tree species that lead to their differences in susceptibility to P. cinnamomi. By using micropropagated clonal plants, we tried to minimize the plant-to-plant differences in the defense response that is maximized by the high intraspecific genetic variability inherent to the Quercus genus. The evolution on the content of Phytophthora proteins in the roots during the first 36 h after inoculation suggests a slower infection process in Q. variabilis plants. These plants displayed a significant decrease in sugars in the roots, together with a downregulation of proteins related to carbon metabolism. In the leaves, the biggest changes in proteomic profiling were observed 16 h after inoculation, and included increased abundance of peroxidases, superoxide dismutases and glutathione S-transferases in Q. variabilis plants, which probably contributed to decrease its susceptibility to P. cinnamomi.

Tuber elevatireticulatum sp. nov., a new species of whitish truffle from Taiwan.

BACKGROUND: There are estimated 180-220 species of Tuber described in the world, but the diversity of the genus in Taiwan is poorly known, with only two species recorded, i.e., Tuber formosanum and T. furfuraceum. During our survey of hypogenous fungi in Taiwan, a whitish truffle belongs to Puberulum clade was collected from roots of Keteleeria fortunei var. cyclolepis in central Taiwan and appeared to differ from the two recorded species. RESULTS: The whitish truffle is herein described as a new species Tuber elevatireticulatum, which is distinguished from closely resembled Asian whitish truffles species like Tuber thailandicum, T. panzhihuanense, T. latisporum and T. sinopuberulum by the association with Keteleeria host, small light brown ascocarps with a dark brown gleba, dark brownish and elliptical ascospores ornamented with a prominently raised alveolate reticulum. Molecular phylogenetic analyses of both ITS and LSU loci clearly supports T. elevatireticulatum as a new species without any significant incongruence. CONCLUSIONS: The whitish truffle is herein described as a new species T. elevatireticulatum based on the evidence from morphology and DNA sequences. T. elevatireticulatum is the first scientific record of whitish truffle in Taiwan.

Evaluation of dazomet as fumigant for the control of brown root rot disease.

BACKGROUND: Brown root rot disease caused by Phellinus noxius is widespread in approximately 216 tree and plant species in tropical and subtropical countries. No direct means of protection against P. noxius infection have thus far been developed. Therefore, in this field survey, a method was developed for preventing and controlling brown root rot disease using fumigation with dazomet. RESULTS: Tracers were used to monitor the effect of dazomet fumigation. The results from field surveys and phytotoxicity tests showed that dazomet is able to kill P. noxius without any side effects on plants. CONCLUSION: The use of an environmentally friendly agent to control brown root rot disease is needed, and prevention of the disease is more important than treatment. Hence, chemical fumigation with 60 g m(-2) of 98% dazomet may be a possible means of preventing P. noxius incursion in agriculture, gardening and agroforestry.