Novel species of fungi described in the present study include the following from Malaysia: Castanediella eucalypti from Eucalyptus pellita, Codinaea acacia from Acacia mangium, Emarcea eucalyptigena from Eucalyptus brassiana, Myrtapenidiella eucalyptorum from Eucalyptus pellita, Pilidiella eucalyptigena from Eucalyptus brassiana and Strelitziana malaysiana from Acacia mangium. Furthermore, Stachybotrys sansevieriicola is described from Sansevieria ehrenbergii (Tanzania), Phacidium grevilleae from Grevillea robusta (Uganda), Graphium jumulu from Adansonia gregorii and Ophiostoma eucalyptigena from Eucalyptus marginata (Australia), Pleurophoma ossicola from bone and Plectosphaerella populi from Populus nigra (Germany), Colletotrichum neosansevieriae from Sansevieria trifasciata, Elsinoë othonnae from Othonna quinquedentata and Zeloasperisporium cliviae (Zeloasperisporiaceae fam. nov.) from Clivia sp. (South Africa), Neodevriesia pakbiae, Phaeophleospora hymenocallidis and Phaeophleospora hymenocallidicola on leaves of a fern (Thailand), Melanconium elaeidicola from Elaeis guineensis (Indonesia), Hormonema viticola from Vitis vinifera (Canary Islands), Chlorophyllum pseudoglobossum from a grassland (India), Triadelphia disseminata from an immunocompromised patient (Saudi Arabia), Colletotrichum abscissum from Citrus (Brazil), Polyschema sclerotigenum and Phialemonium limoniforme from human patients (USA), Cadophora vitícola from Vitis vinifera (Spain), Entoloma flavovelutinum and Bolbitius aurantiorugosus from soil (Vietnam), Rhizopogon granuloflavus from soil (Cape Verde Islands), Tulasnella eremophila from Euphorbia officinarum subsp. echinus (Morocco), Verrucostoma martinicensis from Danaea elliptica (French West Indies), Metschnikowia colchici from Colchicum autumnale (Bulgaria), Thelebolus microcarpus from soil (Argentina) and Ceratocystis adelpha from Theobroma cacao (Ecuador). Myrmecridium iridis (Myrmecridiales ord. nov., Myrmecridiaceae fam. nov.) is also described from Iris sp. (The Netherlands). Novel genera include (Ascomycetes): Budhanggurabania from Cynodon dactylon (Australia), Soloacrosporiella, Xenocamarosporium, Neostrelitziana and Castanediella from Acacia mangium and Sabahriopsis from Eucalyptus brassiana (Malaysia), Readerielliopsis from basidiomata of Fuscoporia wahlbergii (French Guyana), Neoplatysporoides from Aloe ferox (Tanzania), Wojnowiciella, Chrysofolia and Neoeriomycopsis from Eucalyptus (Colombia), Neophaeomoniella from Eucalyptus globulus (USA), Pseudophaeomoniella from Olea europaea (Italy), Paraphaeomoniella from Encephalartos altensteinii, Aequabiliella, Celerioriella and Minutiella from Prunus (South Africa). Tephrocybella (Basidiomycetes) represents a novel genus from wood (Italy). Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

Phenolic secondary metabolites are often thought to protect plants against attack by microbes, but their role in defense against pathogen infection in woody plants has not been investigated comprehensively. We studied the biosynthesis, occurrence, and antifungal activity of flavan-3-ols in black poplar (Populus nigra), which include both monomers, such as catechin, and oligomers, known as proanthocyanidins (PAs). We identified and biochemically characterized three leucoanthocyanidin reductases and two anthocyanidin reductases from P. nigra involved in catalyzing the last steps of flavan-3-ol biosynthesis, leading to the formation of catechin [2,3-trans-(+)-flavan-3-ol] and epicatechin [2,3-cis-(2)-flavan-3-ol], respectively. Poplar trees that were inoculated with the biotrophic rust fungus (Melampsora larici-populina) accumulated higher amounts of catechin and PAs than uninfected trees. The de novo-synthesized catechin and PAs in the rust-infected poplar leaves accumulated significantly at the site of fungal infection in the lower epidermis. In planta concentrations of these compounds strongly inhibited rust spore germination and reduced hyphal growth. Poplar genotypes with constitutively higher levels of catechin and PAs as well as hybrid aspen (Populus tremula 3 Populus alba) overexpressing the MYB134 transcription factor were more resistant to rust infection. Silencing PnMYB134, on the other hand, decreased flavan-3-ol biosynthesis and increased susceptibility to rust infection. Taken together, our data indicate that catechin and PAs are effective antifungal defenses in poplar against foliar rust infection.

Poplar trees synthesize flavan-3-ols (catechin and proanthocyanidins) as a defense against foliar rust fungi, but the regulation of this defense response is poorly understood. Here, we investigated the role of hormones in regulating flavan-3-ol accumulation in poplar during rust infection. We profiled levels of defense hormones, signaling genes, and flavan-3-ol metabolites in black poplar leaves at different stages of rust infection. Hormone levels were manipulated by external sprays, genetic engineering, and drought to reveal their role in rust fungal defenses. Levels of salicylic acid (SA), jasmonic acid, and abscisic acid increased in rust-infected leaves and activated downstream signaling, with SA levels correlating closely with those of flavan-3-ols. Pretreatment with the SA analog benzothiadiazole increased flavan-3-ol accumulation by activating the MYB-bHLH-WD40 complex and reduced rust proliferation. Furthermore, transgenic poplar lines overproducing SA exhibited higher amounts of flavan-3-ols constitutively via the same transcriptional activation mechanism. These findings suggest a strong association among SA, flavan-3-ol biosynthesis, and rust resistance in poplars. Abscisic acid also promoted poplar defense against rust infection, but likely through stomatal immunity independent of flavan-3-ols. Jasmonic acid did not confer any apparent defense responses to the fungal pathogen. We conclude that SA activates flavan-3-ol biosynthesis in poplar against rust infection.

Brassicales plants produce glucosinolates and myrosinases that generate toxic isothiocyanates conferring broad resistance against pathogens and herbivorous insects. Nevertheless, some cosmopolitan fungal pathogens, such as the necrotrophic white mold Sclerotinia sclerotiorum, are able to infect many plant hosts including glucosinolate producers. Here, we show that S. sclerotiorum infection activates the glucosinolate-myrosinase system, and isothiocyanates contribute to resistance against this fungus. S. sclerotiorum metabolizes isothiocyanates via two independent pathways: conjugation to glutathione and, more effectively, hydrolysis to amines. The latter pathway features an isothiocyanate hydrolase that is homologous to a previously characterized bacterial enzyme, and converts isothiocyanate into products that are not toxic to the fungus. The isothiocyanate hydrolase promotes fungal growth in the presence of the toxins, and contributes to the virulence of S. sclerotiorum on glucosinolate-producing plants.

-Acyl sugars (-AS) are abundant trichome-specific metabolites that function as indirect defenses against herbivores of the wild tobacco ; whether they also function as generalized direct defenses against herbivores and pathogens remains unknown. We characterized natural variation inAS among 26 accessions and examined their influence on two native fungal pathogens, U4 and sp. U10, and the specialist herbivore At least 15 differentAS structures belonging to three classes were found in leaves. A 3-fold quantitative variation in total leafAS was found among the natural accessions. Experiments with natural accessions and crosses between high- and low-AS accessions revealed that total AS levels were associated with resistance against herbivores and pathogens. RemovingAS from the leaf surface increased growth rate and plant fungal susceptibility.-AS supplementation in artificial diets and germination medium reduced growth and fungal spore germination, respectively. Finally, silencing the expression of a putative branched-chain α-ketoacid dehydrogenase E1 β-subunit-encoding gene () in the trichomes reduced total leaf AS by 20% to 30% and increased susceptibility to pathogens. We conclude that AS function as direct defenses to protect plants from attack by both native pathogenic fungi and a specialist herbivore and infer that their diversification is likely shaped by the functional interactions among these biotic stresses.

Conifer forests worldwide are becoming increasingly vulnerable to attacks by bark beetles and their fungal associates due to the effects of global warming. Attack by the bark beetle Ips typographus and the blue-stain fungus it vectors ( Endoconidiophora polonica ) on Norway spruce ( Picea abies ) is well known to induce increased production of terpene oleoresin and polyphenolic compounds. However, it is not clear whether specific compounds are important in resisting attack. In this study, we observed a significant increase in dihydroflavonol and flavan-3-ol content after inoculating Norway spruce with the bark beetle vectored fungus. A bioassay revealed that the dihydroflavonol taxifolin and the flavan-3-ol catechin negatively affected both I. typographus and E. polonica . The biosynthesis of flavan-3-ols is well studied in Norway spruce, but little is known about dihydroflavonol formation in this species. A flavanone-3-hydroxylase (F3H) was identified that catalyzed the conversion of eriodictyol to taxifolin and was highly expressed after E. polonica infection. Down-regulating F3H gene expression by RNA interference in transgenic Norway spruce resulted in significantly lower levels of both dihydroflavonols and flavan-3-ols. Therefore F3H plays a key role in the biosynthesis of defense compounds in Norway spruce that act against the bark beetle-fungus complex. This enzyme forms a defensive product, taxifolin, which is also a metabolic precursor of another defensive product, catechin, which in turn synergizes the toxicity of taxifolin to the bark beetle associated fungus.

Summary Strigolactones (SLs) are carotenoid‐derived plant hormones that also act in the rhizosphere to stimulate germination of root‐parasitic plants and enhance plant symbiosis with beneficial microbes. Here, the role of SLs was investigated in the interaction of rice (Oryza sativa) roots with the root‐knot nematode Meloidogyne graminicola. Genetic approaches and chemical sprays were used to manipulate SL signaling in rice before infection with M. graminicola. Then, nematode performance was evaluated and plant defense hormones were quantified. Meloidogyne graminicola infection induced SL biosynthesis and signaling and suppressed jasmonic acid (JA)‐based defense in rice roots, suggesting a potential role of SLs during nematode infection. Whereas the application of a low dose of the SL analogue GR24 increased nematode infection and decreased jasmonate accumulation, the SL biosynthesis and signaling d mutants were less susceptible to M. graminicola, and constitutively accumulated JA and JA‐isoleucine compared with wild‐type plants. Spraying with 0.1 μM GR24 restored nematode susceptibility in SL‐biosynthesis mutants but not in the signaling mutant. Furthermore, foliar application of the SL biosynthesis inhibitor TIS108 impeded nematode infection and increased jasmonate levels in rice roots. In conclusion, SL signaling in rice suppresses jasmonate accumulation and promotes root‐knot nematode infection.

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