Since the 1990s, brown root rot caused by Phellinus noxius (Corner) Cunningham has become a major tree disease in Taiwan. This fungal pathogen can infect more than 200 hardwood and softwood tree species, causing gradual to fast decline of the trees. For effective control, we must determine how the pathogen is disseminated and how the new infection center of brown root rot is established. We performed Illumina sequencing and de novo assembly of a single basidiospore isolate Daxi42 and obtained a draft genome of ~40 Mb. By comparing the 12,217 simple sequence repeat (SSR) regions in Daxi42 with the low-coverage Illumina sequencing data for four additional P. noxius isolates, we identified 154 SSR regions with potential polymorphisms. A set of 13 polymorphic SSR markers were then developed and used to analyze 329 P. noxius isolates collected from 73 tree species from urban/agricultural areas in 14 cities/counties all around Taiwan from 1989 to 2012. The results revealed a high proportion (~98%) of distinct multilocus genotypes (MLGs) and that none of the 329 isolates were genome-wide homozygous, which supports a possible predominant outcrossing reproductive mode in P. noxius. The diverse MLGs exist as discrete patches, so brown root rot was most likely caused by multiple clones rather than a single predominant strain. The isolates collected from diseased trees near each other tend to have similar genotype(s), which indicates that P. noxius may spread to adjacent trees via root-to-root contact. Analyses based on Bayesian clustering, F ST statistics, analysis of molecular variance, and isolation by distance all suggest a low degree of population differentiation and little to no barrier to gene flow throughout the P. noxius population in Taiwan. We discuss the involvement of basidiospore dispersal in disease dissemination.
Entomopathogenic fungi have been used for biocontrol of insect pests for many decades. However, the efficacy of such fungi in field trials is often inconsistent, mainly due to environmental stresses, such as UV radiation, temperature extremes, and desiccation. To circumvent these hurdles, metabolic engineering of dihydroxynaphthalene (DHN) melanin biosynthetic genes (polyketide synthase, scytalone dehydratase, and 1,3,8-trihydroxynaphthalene reductase genes) cloned from Alternaria alternata were transformed into the amelanotic entomopathogenic fungus Metarhizium anisopliae via Agrobacterium-mediated transformation. Melanin expression in the transformant of M. anisopliae was verified by spectrophotometric methods, liquid chromatography/mass spectrometry (LC/MS), and confocal microscopy. The transformant, especially under stresses, showed notably enhanced antistress capacity and virulence, in terms of germination and survival rate, infectivity, and reduced median time to death (LT 50 ) in killing diamondback moth (Plutella xylostella) larvae compared with the wild type. The possible mechanisms in enhancing the stress tolerance and virulence, and the significance and potential for engineering melanin biosynthesis genes in other biocontrol agents and crops to improve antistress fitness are discussed.Although chemical pesticides can kill a wide range of insect pests rapidly and cost-effectively, their side effects over time are problematic. The selective pressure from long-term application of chemical pesticides ultimately leads to pesticide resistance, harm to the ecosystem, and residual poisonous effects on humans and animals (9).
Strawberry is a small fruit crop with high economic value. Anthracnose caused by Colletotrichum spp. poses a serious threat to strawberry production, particularly in warm and humid climates, but knowledge of pathogen populations in tropical and subtropical regions is limited. to investigate the diversity of infectious agents causing strawberry anthracnose in taiwan, a disease survey was conducted from 2010 to 2018, and Colletotrichum spp. were identified through morphological characterization and multilocus phylogenetic analysis with internal transcribed spacer, glyceraldehyde 3-phosphate dehydrogenase, chitin synthase, actin, beta-tubulin, calmodulin, and the intergenic region between Apn2 and MAT1-2-1 (ApMAT). Among 52 isolates collected from 24 farms/nurseries in taiwan, a new species, Colletotrichum miaoliense sp. nov. (6% of all isolates), a species not previously known to be associated with strawberry, Colletotrichum karstii (6%), and three known species, Colletotrichum siamense (75%), Colletotrichum fructicola (11%), and Colletotrichum boninense (2%), were identified. The predominant species C. siamense and C. fructicola exhibited higher mycelial growth rates on potato dextrose agar and caused larger lesions on wounded and non-wounded detached strawberry leaves. Colletotrichum boninense, C. karstii, and C. miaoliense only caused lesions on wounded leaves. Understanding the composition and biology of the pathogen population will help in disease management and resistance breeding. Strawberry (Fragaria × ananassa Duch.) is a popular small fruit crop with high economic and nutritive value. Strawberry is in high demand globally. From 2008 to 2018, the annual worldwide cultivation of strawberries increased from approximately 400 to 483 thousand hectares 1. Although strawberries are native to temperate regions, they can also be grown in tropical and subtropical regions (sometimes under high-altitude conditions). The land areas devoted to strawberry cultivation in Colombia,
The order Hymenochaetales of white rot fungi contain some of the most aggressive wood decayers causing tree deaths around the world. Despite their ecological importance and the impact of diseases they cause, little is known about the evolution and transmission patterns of these pathogens. Here, we sequenced and undertook comparative genomic analyses of Hymenochaetales genomes using brown root rot fungus Phellinus noxius, wood-decomposing fungus Phellinus lamaensis, laminated root rot fungus Phellinus sulphurascens and trunk pathogen Porodaedalea pini. Many gene families of lignin-degrading enzymes were identified from these fungi, reflecting their ability as white rot fungi. Comparing against distant fungi highlighted the expansion of 1,3-beta-glucan synthases in P. noxius, which may account for its fast-growing attribute. We identified 13 linkage groups conserved within Agaricomycetes, suggesting the evolution of stable karyotypes. We determined that P. noxius has a bipolar heterothallic mating system, with unusual highly expanded ~60 kb A locus as a result of accumulating gene transposition. We investigated the population genomics of 60 P. noxius isolates across multiple islands of the Asia Pacific region. Whole-genome sequencing showed this multinucleate species contains abundant poly-allelic single nucleotide polymorphisms with atypical allele frequencies. Different patterns of intra-isolate polymorphism reflect mono-/heterokaryotic states which are both prevalent in nature. We have shown two genetically separated lineages with one spanning across many islands despite the geographical barriers. Both populations possess extraordinary genetic diversity and show contrasting evolutionary scenarios. These results provide a framework to further investigate the genetic basis underlying the fitness and virulence of white rot fungi.
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