Davi Mesquita de Macedo

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

Background 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 Microcyclus sexual morph in the Planistromellaceae and the two purported asexual morphs - Fusicladium and Aposphaeria – 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. Methods and Results 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 Pseudocercospora s. str., now accepted as one of the distinct genera within Mycosphaerellaceae. The new combination Pseudocercospora ulei is proposed and the life cycle of the fungus is confirmed, based on both experimental and phylogenetic evidence, with the Aposphaeria morph shown to have a spermatial rather than an infective-dispersal function. Conclusions 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.

Mycobiota of the weed Tradescantia fluminensis in its native range in Brazil with particular reference to classical biological control

Tradescantia fluminensis [Commelinaceae] (common name wandering Jew or trad), is a native Brazilian herbaceous plant, which has been introduced to be used as an ornamental in many warm areas of the world. In New Zealand and other countries it has become an aggressive invader of natural ecosystems, causing serious environmental disturbances and threatening biodiversity. Surveys of pathogen and insect natural enemies of T. fluminensis were conducted over several years in Brazil to identify potential candidates for use as classical biological control agents in New Zealand. The surveys found seven pathogenic fungi associated with T. fluminensis and related Tradescantia species: Cercospora apii (leaf spot), Rhizoctonia solani (leaf blight), Sclerotium rolfsii (crown rot) and Uromyces commelinae (rust), and three novel species described in this paper: Ceratobasidium tradescantiae sp. nov. (web blight), Colletotrichum riograndense sp. nov. (anthracnose) and Kordyana brasiliensis sp. nov. (white smut-like disease). Observations of damage in the field and expected host-range suggest that K. brasiliensis and U. commelinae have the highest potential for use as classical biological control agents.

Podridão-mole em pós-colheita de batata (Solanum tuberosum) incitada por Pseudomonas viridiflava

A soft rot inducing bacterium was isolated from decaying potato tubers and attempts were made to identify it at species level. Biochemical, biological and staining procedures allowed to identify it as belonging to the species Pseudomonas viridiflava. Additionally, the potential pathogenicity and host range of the identified isolate was checked by artificial inoculation of storage organs of different plants. This paper showed and confirmed that phytobacteria other than Pectobacterium spp are able to induce soft rot and that this fact deserves further investigation as far as crop losses due to prokaryotes are concerned.

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.

Cercospora neomaricae sp. nov. causing leaf spots on Neomarica caerulea

The new species Cercospora neomaricae was found causing leaf spot on Neomarica caerulea (walking iris or apostle plant) and is described. Pathogenicity to N. caerulea was also demonstrated.

Pseudocercospora lonicerigena a leaf spot fungus on the invasive weed Lonicera japonica in Brazil

Lonicera japonica (Japanese honeysuckle), a plant of Asian origin introduced as an ornamental into many countries, has become an invasive weed in some exotic situations, such as in southern Brazil. Classical biological control (CBC) with natural enemies collected in the centre of origin is considered to be the best alternative for sustainable management of L. japonica. In the context of this strategy, previous knowledge of the natural enemies already present in the target area is of great importance in order to avoid un-necessary introductions of CBC agents from the weed’s native range. Recently, examination of populations of L. japonica in localities in the Brazilian states of Rio de Janeiro and Paraná revealed the presence of leaf spots consistently associated with a cercosporoid hyphomycete. A molecular and morphological study of this fungus led to its recognition as Pseudocercospora lonicerigena. There were few differences when the Brazilian isolate was compared with a strain found in North America. This is the first report of this fungus in Brazil. The fungus was isolated in pure culture and inoculation of healthy leaves of L. japonica eventually led to leaf yellowing and necrosis, indicating that P. lonicerigena is not highly pathogenic, as evidenced by the continuing advance of this weed in southern Brazil. Therefore, the introduction of additional co-evolved natural enemies collected in Asia, perhaps piggy-backing on an ongoing project already underway in New Zealand, will be necessary to control this invasive alien weed in Brazil.

Reappraisal and neotypification of Phyllachora feijoae.

Acca sellowiana (Myrtaceae), feijoa (in Brazil, goiaba da serra), is a native southern South America tree that produces edible fruits which, although only occasionally cultivated in South America, became a significant fruit crop in New Zealand. Recently, during surveys for fungal pathogens of feijoa in southern Brazil, several plants were found bearing tar-spot symptoms caused by a species of Phyllachora. A literature search enabled us to identify the fungus as Phyllachora feijoae, a little-known species originally described in the 19th century by H. Rehm and later transferred to the genus Catacauma. The name Catacauma feijoae, although now regarded as a later synonym of P. feijoae is still mistakenly in use (as, for instance, in the Brazilian list of fungi on plants). The type specimen was most probably deposited in the Botanisches Garten und Museum Berlin-Dahlem (B) and lost or destroyed during World War II, and could not be located. The recent recollection of abundant material of this fungus in the vicinity of Pelotas (Rio Grande do Sul, Brazil) allowed its re-examination and neotypification. Phyllachora feijoae is also illustrated here for the first time.

Leaf spot on Clerodendrum x speciosus in Brazil caused by Pseudocercospora clerodendricola sp. nov.

Pseudocercospora clerodendricola sp. nov. is described herein. The fungus was found causing leaf spots in Clerodendrum x speciosum (bleeding heart) and its pathogenicity was demonstrated. Inoculation with culture discs placed on healthy leaves resulted in typical leaf spots appearing 30 days after inoculation.