Mycobiota of Schinus terebinthifolius, Tradescantia fluminensis and Rottboellia cochinchinensis as potential biological control agents

A invasão de plantas exóticas representa uma das maiores ameaças para a biodiversidade do planeta. Muitos países enfrentam situações graves com invasões biológicas promovidas por plantas nativas do Brasil que, depois de introduzidas a partir de seu centro de origem, livres de seus inimigos naturais, passaram a invadir ecossistemas naturais ameaçando a sua integridade e processos ecológicos fundamentais. A utilização das medidas de controle convencionais, utilizadas na agricultura é, nesses casos, contra- indicada ou inviável. O controle biológico clássico pela introdução de inimigos naturais específicos provenientes do centro de origem da planta é a única opção que apresenta exemplos de sucesso duradouro e é reconhecidamente sustentável. Fungos associados a três espécies de plantas invasoras (Rottboellia cochinchinensis capim-camalote, Tradescantia fluminensis trapoeraba branca e Schinus terebinthifolius aroeira) foram estudados no contexto do controle biológico clássico com o propósito de contribuir para a mitigação de invasões nos EUA e Nova Zelândia e os resultados são aqui apresentados. Um hifomiceto foi descoberto atacando R. cochinchinensis no Brasil e sua identidade foi esclarecida como sendo Bipolaris chloridis. Este fungo nunca havia sido antes relatado no Brasil e nem sobre este hospedeiro. Ele se mostrou capaz de atacar outras gramíneas além de R. cochinchinensis, milho e capim de Rhodes (seu hospedeiro originalmente conhecido). As implicações desta descoberta para o controle biológico foram discutidas. Sobre T. fluminensis foram encontrados nove espécies de fungos durante o levantamento: Cercospora apii, Ceratobasidium tradescantiae sp. nov., Colletotrichum falcatum, Kordyana brasiliensis sp.nov., Mycosphaerella tradescantiae sp. nov., Rhizoctonia solani, Sclerotium rolfsii, Septoria paranaensis sp. nov. e Uromyces commelinae. A taxonomia da nova espécie Kordyana brasiliensis foi esclarecida por exames morfológicos e estudos moleculares (com a utilização dos primers NL1 e NL4) e o fungo se mostrou promissor como agente de biocontrole, sendo específico para T. fluminensis (entre 69 espécies testadas de 32 famílias botânicas) e capaz de causar uma doença severa sobre este hospedeiro. Sob condições de infecção natural o fungo apresentou uma incidência de doença na ordem de 70% e causou severidade média de 42% em 200 folhas avaliadas. Os levantamentos da micobiota de S. terebinthifolius, revelaram uma grande diversidade de fungos potencialmente fitopatogênicos. Dentre estes, no presente trabalho, examinou- se com atenção os fungos coletados reconhecidos como pertencentes à família Meliolaceae e também, considerando-se o seu aparente potencialpara o controle biológico,um isolado de Corynespora cassiicola causador de doença severa sobre S. terebinthifolius. Três espécies de fungos causadores de míldio negro (uma doença de pequeno impacto sobre S. terebinthifolius) foram encontradas colonizando S. terebinthifolius em várias regiões do Brasil: Irenopsis schini-terebenthifolii sp. nov, Meliola chilensis e Meliola rhois var. africana. A primeira espécie foi reconhecida como nova e descrita enquanto que as duas demais foram reconhecidas como representando novas associações patógeno-hospedeiro, pois os fungos não eram conhecidos ainda sobre S. terebinthifolius. A morfologia de um hifomiceto associado a manchas e queimas foliares de S. terebinthifolius foi reconhecida como equivalente à dos fungos da espécie C. cassiicola e confirmada por métodos moleculares envolvendo a utilização dos primers ITS1 e ITS4. Além disso, foi realizado um teste de especificidade envolvendo 23 espécies de plantas de diferentes famílias botânicas, inclusive Anacardiaceae, e o patotipo se mostrou especifico a S. terebinthifolius, sendo proposto o seu reconhecimento como C. cassiicola f. sp. schinii e também o seu potencial para utilização como agente de controle biológico para infestações de S. terebinthifolius na Flórida e Havaí (EUA).Invansions of natural ecosystems by exotic plants represent one of the greatest threats to biodiversity. Many countries face serious problems with such biological invasions involving plants that are native from Brazil. After its having been introduced from their center of origin and free from their natural enemies they invade natural ecosystems and threaten the integrity of ecological processes. The conventional control measures used in agriculture, in ssuch cases, are not viable nor recommended. The classical biological control involving the introduction of specific natural enemies from the center of origin of the plant is the only option that provides examples of success and is widely recognized as the sole sustainable alternative. Fungi associated with three weed species (Rottboellia cochinchinensis - Itchgrass, Tradescantia fluminensis - wandering jew and Schinus terebinthifolius - brazilian pepper tree) were studied in the context of biological control with the aim of contributing to the mitigation of invasions in the U.S., New Zealand and Brazil and the results are presented herein. A hyphomycete was discovered attacking R. cochinchinensis and identified as Bipolaris chloridis. This fungus has never been reported before from Brazil nor on this host. This fungus was able to attack other grasses besides R. cochinchinensis, namely corn and rhodes grass (its original host ). The implications of these finding for biological control were discussed. In T. fluminensis, nine species of fungi were collected during the survey: Cercospora apii, Ceratobasidium tradescantiae sp. nov., Colletotrichum falcatum, Kordyana brasiliensis sp. nov., Mycosphaerella tradescantiae sp. nov., Rhizoctonia solani, Sclerotium rolfsii, Septoria paranaensis sp. nov. and Uromyces commelinae. The taxonomy of the new species Kordyana brasiliensis was clarified by examinations of morphological characters and molecular studies (using the primers NL1 and NL4). This fungus was regarded as showing a high potential for use in biocontrol agent. It was specific to T. fluminensis (among 69 species tested from 32 botanical families) and capable of causing severe disease on this host. Under conditions of natural infection bu this fungus an incidence of 70% and a level of 42% of disease severity was reached. Surveys of the mycoflora S. terebinthifolius showed a great diversity of potentially pathogenic fungi among which are fungi belonging to a poorly known group of ascomycetes causing black mildews, the Meliolaceae. Three species were found on this host: Irenopsis schini- terebenthifolii sp. nov., Meliola chilensis and Meliola rhois var. africana. The first species was described as new whereas the other two were new host-pathogen associations. The potential for practical application in biological control of an isolate of Corynespora cassiicola found causing a severe disease on S. terebinthifolius. was investigated. Its identity was confirmed as C. cassiicola by a combination of morphology studies and molecular methods involving the use of primers ITS1 and ITS4. In addition, we performed a specificity test involving 23 species of plants of different botanical families, including several Anacardiaceae. The isolate from S. terebinthifolius was shown to be host- specific and the new forma specialis C. cassiicola f. sp. schinii was proposed. Its potential for use as biological control agent for infestations of S. terebinthifolius in Florida and Hawaii (USA) was regarded as high.Fundação de Amparo à Pesquisa do Estado de Minas Gerai

First record of Botryosphaeria ribis associated with leaf spots on Magnolia aff. candollei in Brazil

A leaf spot disease was observed attacking some Magnolia aff. candollei plants grown in a private garden in the city of Rio de Janeiro, RJ, Brazil. Such leaf spots coalesced and led to extensive blight of foliage. A fungus was clearly associated to the disease symptoms and was identified as Botryosphaeria ribis. Its anamorph, Fusicoccum ribis, was also present, although less abundant than the teleomorph. This is first report of this fungus on this host in Brazil and the first record of any fungal disease on a member of the genus Magnolia in Brazil

Erasing the Past: A New Identity for the Damoclean Pathogen Causing South American Leaf Blight of Rubber

<div><p>Background</p><p>South American leaf blight (SALB) of rubber has been the main constraint to production in its neotropical centre of origin since commercial plantations were first established. The fungal causal agent was identified and described more than a century ago but its precise placement within the Ascomycota still remains uncertain. Indeed, such is the ambiguity surrounding the pathogen that each of the spore morphs would, according to their present classification, be placed in different ascomycete families: the <i>Microcyclus</i> sexual morph in the Planistromellaceae and the two purported asexual morphs - <i>Fusicladium</i> and <i>Aposphaeria</i> – in the Venturiaceae and Lophiostomataceae, respectively. Given the historical importance of the fungus and the ever-menacing threat that it poses to rubber production in the Palaeotropics – and, thus to the rubber industry and to the global economy – its phylogeny, as well as its biology, should be resolved as a matter of urgency.</p><p>Methods and Results</p><p>Here, six genomic regions (LSU rRNA, mtSSU, MCM7, EF-1α, Act and ITS) were used for reconstructing the molecular phylogeny of the SALB fungus based on material collected throughout Brazil. The analyses support the classification of the fungus in the family Mycosphaerellaceae s. str. (Capnodiales, Dothideomycetes) and place it firmly within the clade <i>Pseudocercospora</i> s. str., now accepted as one of the distinct genera within Mycosphaerellaceae. The new combination <i>Pseudocercospora ulei</i> is proposed and the life cycle of the fungus is confirmed, based on both experimental and phylogenetic evidence, with the <i>Aposphaeria</i> morph shown to have a spermatial rather than an infective-dispersal function.</p><p>Conclusions</p><p>Because the phylogeny of the SALB fungus has now been clarified, new insights of its epidemiology and genomics can be gained following comparison with closely-related, better-researched crop pathogens.</p></div

Origin of the <i>Microcyclus ulei</i> isolates used in the phylogenetic study.

1<p>Brazilian states: Acre (AC), Bahia (BA), Espírito Santo (ES), Mato Grosso (MT), Minas Gerais (MG) and Rondônia (RO).</p

Pleomorphic development of the life cycle of <i>Pseudocercospora ulei</i>.

<p>Weighted average based on the score of conidial sporulation intensity and spermogonia and ascostromata density during the leaf development of RO38 rubber clone grown under field conditions. Assessments were made from December 15, 2011 to February 24, 2012 (A); and from September 19 to December 3, 2012 (B).</p

Bayesian analysis showing the phylogenetic relationships of <i>Microcyclus ulei</i> based on the MCM7 sequence alignment.

<p>Bayesian posterior probabilities are given at the nodes and coded according to the colored scale bar. The black line scale bar shows 0.2 expected changes per site. The tree was rooted with <i>Aspergillus niger</i>.</p

Hypothetical life cycle of <i>Pseudocercospora ulei</i>.

<p><b>A</b>. Asexual morph with conidiophores and conidia (Bar =  35µm) and conidiogenous cells with conidia at different stages of conidial formation. Pictures: Lesions to which the asexual morph is associated (left) and close-up of leaf bearing typical lesions (right). <b>B</b>. Spermogonial morph with stroma, spermogonia (Bar =  30 µm) and spermatia (Bar =  7 µm). Pictures: Lesions to which the spermogonial morph is associated (left), and close-up of the same lesions (right). <b>C</b>. Sexual morph with stroma, pseudothecia, asci and ascospores (Bar = 60µm). Pictures: Lesions to which the sexual morph is associated (left), and close-up of stromata (right). Dotted arrows indicate that both ascospores and conidia can infect young leaves.</p