Rita C. Pereira-Carvalho

An overlooked source of fungal diversity: novel hyphomycete genera on trichomes of cerrado plants.

Eight monotypic hyphomycete genera new to science are described from the trichomes of native plants growing in the cerrado of Brazil: Trichomatoclava cerradensis, Echinoconidiophorum cerradense, Globoconidiopsis cerradensis, Globoconidium cerradense, Helminthosporiomyces cerradensis, Trichomatosphaera [corrected] cerradensis , Phragmoconidium cerradense, and Vesiculohyphomyces cerradensis gens. spp. nov. Two of the new genera were found on hosts belonging in Myrtaceae, and one of each of the following families: Icacinaceae, Malphigiaceae, Fabaceae, Dilleniaceae, Chrysobalanaceae, and Caryocaraceae. These discoveries suggest that the trichomes of neotropical plants are an unexplored source of novel fungal diversity, and merit more attention in biodiversity surveys.

Recessive Resistance Derived from Tomato cv. Tyking-Limits Drastically the Spread of Tomato Yellow Leaf Curl Virus.

The tomato yellow leaf curl disease (TYLCD) causes severe damage to tomato (Solanum lycopersicum L.) crops throughout tropical and subtropical regions of the world. TYLCD is associated with a complex of single-stranded circular DNA plant viruses of the genus Begomovirus (family Geminiviridae) transmitted by the whitefy Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae). The tomato inbred line TX 468-RG is a source of monogenic recessive resistance to begomoviruses derived from the hybrid cv. Tyking F1. A detailed analysis of this germplasm source against tomato yellow leaf curl virus-Israel (TYLCV-IL), a widespread TYLCD-associated virus, showed a significant restriction to systemic virus accumulation even under continuous virus supply. The resistance was effective in limiting the onset of TYLCV-IL in tomato, as significantly lower primary spread of the virus occurred in resistant plants. Also, even if a limited number of resistant plants could result infected, they were less efficient virus sources for secondary spread owing to the impaired TYLCV-IL accumulation. Therefore, the incorporation of this resistance into breeding programs might help TYLCD management by drastically limiting TYLCV-IL spread.

Breeding for Resistance to Viral Diseases

Genetic resistance to viruses and/or their vectors is the most practical and efficient method of disease control. Therefore, significant research effort has been devoted to this field. In fact, great achievements in breeding plants for virus resistance have been made using classical and molecular breeding approaches. The biggest obstacle for these breeding programs is to identify and incorporate, on a large scale, multiple resistance factors in elite genetic materials and anticipate potential problems with emerging viral diseases in association with the challenges that climate change is bringing to food production. The development of dense genetic maps, with molecular markers in strong linkage disequilibrium with virus resistance alleles, has enabled the establishment of marker-assisted selection of superior genotypes and the isolation and cloning of many virus resistance genes. Such studies have been facilitated in some of the species for which complete genome sequences are now available. Moreover, the knowledge about viral genes and genomes has been used in the development of resistant transgenic plants and they have been effective in different pathosystems; paving the way towards a new collection of anti-viral biotech breeding strategies.

Plurispermiopsis: a new capnodiaceous genus from the Brazilian Cerrado

A new ascomycete genus placed in family Capnodiaceae found in the Brazilian Cerrado is described and designated Plurispermiopsis, type species P. cerradensis.

Fluorescence in situ hybridization analysis of endosymbiont genera reveals novel infection patterns in a tomato-infesting Bemisia tabaci population from Brazil

The Bemisia tabaci cryptic species complex harbors a diversified flora of primary and secondary endosymbionts, which plays crucial roles in many aspects of the insect biology. The endosymbiont infection pattern is dependent upon many factors, including host plant and geographic origin. In Brazil, the invasion of B. tabaci Middle East-Asia Minor-1 (MEAM 1) populations was observed in tomato (Solanum lycopersicum L.) fields in the 1990s, which was followed by severe begomovirus epidemics. Here we confirmed the vertical transmission of “Candidatus Portiera” and the localization of secondary endosymbionts in distinct B. tabaci developmental stages. Hamiltonella defensa was detected in bacteriocytes but also scattered in the leg muscles as well as in the male heads. Wolbachia-specific signals were found in eggs, nymphs, male adults, and female gonads in predominant association with bacteriocytes. These results were somewhat surprising since Wolbachia infection is rarely found in MEAM 1 populations from the Old World. Our results reinforce the notion that endosymbiont infection pattern may vary according to the insect population, gender, developmental stage, and geographic origin. This characterization will provide tools to study the endosymbiont function in the transmission ability/efficiency of a complex of tomato-infecting bipartite begomoviruses by B. tabaci under Neotropical conditions.

Complete Genome Sequences of Sweet potato feathery mottle virus and Sweet potato virus G from Brazil

ABSTRACT In Brazil, Potyvirus species in sweet potatoes have been detected mostly by serology. Here, we report the complete genome sequences of two Potyvirus species, Sweet potato feathery mottle virus strain (SPFMV-UNB-01) and Sweet potato virus G strain (SPVG-UNB-01).

New Cercospora species on Jatropha curcas in central Brazil

A new cercosporoid hyphomycete, Cercospora jatrophiphila, herein described and molecularly characterized, was found in Planaltina, DF, Brazil on Jatropha curcas (Euphorbiaceae).