Ivan Paulo Bedendo

Efeito inibitório de extratos vegetais sobre Colletotrichum gloeosporioides - agente causal da podridão de frutos de mamoeiro

To evaluate the effect of plant extracts on the growth and the sporulation of Colletotrichum gloeosporioides, aqueous extracts from garlic, pippermint, castor bean and pepper were obtained and incorporated into potato-dextrose-agar (PDA) at concentrations of 100, 200, 500, 1000, 5000 and 10000 mg/g. Micelial growth and the conidium production were evaluated in these media. All extracts exhibited inhibitory effect at the concentration of 200 mg/g and above. Garlic extracts inhibited micelial growth in the range of 5.3 to 67.6%, it had, however no effect on sporulation. Peppermint, castor bean and pepper extracts promoted micelium inhibition and reduced the conidium production in the range of 41 to 84%, according to the extract concentrations. It was demonstrated that the different extracts have antifungal activities and that they have a potential use as an alternative control in relation to physical or chemical methods.

Detection and identification of the maize bushy stunt phytoplasma in corn plants in Brazil using PCR and RFLP

Plants of corn (Zea mays L.) exhibiting symptoms of stunting and leaf reddening were assayed for the presence of phytoplasma gene sequences through the use of phytoplasma rRNA and ribosomal protein gene and maize bushy stunt (MBS) phytoplasma-specific oligonucleotide primers in polymerase chain reactions (PCR). Polymorphisms in 16S rDNA amplified from diseased plants were those characteristic of phytoplasmas classified in the16S rRNA gene group 16SrI, subgroup IB, of which MBS phytoplasma is a member. Amplification of ribosomal protein (rp) gene sequences in PCR primed by phytoplasma-specific primers confirmed presence of a phytoplasma in the diseased plants. Restriction fragment length polymorphism (RFLP) patterns of the amplified phytoplasma rp gene sequences were similar or identical to those observed for a known strain of MBS phytoplasma. In separate PCR, an MBS-specific oligonucleotide pair primed amplification of a MBS-characteristic DNA from templates derived from the diseased corn. Our data provide the first firm evidence for the presence of maize bushy stunt phytoplasma in corn in Brazil.

Molecular identification of a 16SrIII-B phytoplasma associated with cassava witches’ broom disease

Cassava plants displaying typical symptoms commonly associated with phytoplasmas, such as witches’ broom, general stunt, leaves with chlorosis, deformation, and reduced size, were observed in fields located in the state of São Paulo, Brazil. Molecular analysis using specific primers evidenced that the phytoplasma found in all positive samples was affiliated with group 16SrIII (X-disease group). Based on the virtual RFLP patterns and similarity coefficient calculations, the phytoplasma was classified as a member of the group 16SrIII, subgroup B (16SrIII-B). Phylogenetic analysis showed this phytoplasma as closely related to the reference strain for the subgroup 16SrIII-B. Representatives of 16SrIII-B have been described in several cultivated species in Brazil and cassava is an additional host species for this phytoplasma.

Tomato big bud associated with a phytoplasma belonging to group 16Sr III in Brazil

Abstract Tomato plants displaying foliar chlorosis, shoot proliferation, calyx deformation and reduced leaves, flowers and fruits all symptoms of tomato big bud, were found in a culture at Bragança Paulista region, State of São Paulo, Brazil. Samples were collected and analyzed by electron microscopy, PCR and RFLP to detect and identify the possible phytoplasma associated with diseased plants. Pleomorphic and round corpuscles were observed in the phloem vessels of diseased plants; the presence of phytoplasma was confirmed by PCR using universal primer pairs. PCR assays primed by group-specific primer pairs enabled the identification of the detected phytoplasma as a member of the 16SrIII group. Molecular identification by RFLP using various endonucleases confirmed the classification of this phytoplasma as a representative of the 16SrIII group. Phytoplasmas that are associated with big bud have been classified in different groups. The big bud phytoplasma identified in Brazil belongs to the same group of phytoplasmas associated with tomato big bud in Italy, but it is different from those found in other areas of the world.

Phytoplasma associated with shoot proliferation in begonia

Begonia is a very appreciated genus of ornamental plants, of economic relevancy, having species of flowers and foliage. In commercial croppings, plants exhibiting characteristic symptoms of phytoplasma infection have been observed, such as shoot proliferation, reduced plant, size small leaves and flowers, and phyllody. Leaves were sampled and total DNA was extracted to be used in nested Polymerase Chain Reaction (PCR), in order to detect and identify an expected phytoplasma. The results confirmed consistently the presence of a phytoplasma associated with symptomatic plants through the amplification of a typical genomic fragment of 1.2 kb by using the universal primers R16mF2/mR1 and R16F2n/R2. The use of specific primers R16(III)F2/R1 allowed to identify the phytoplasma detected as a representative of the group 16SrIII. This information is very expressive, because different diseases caused by fungus, bacteria, virus and nematodes have been reported for begonia, however, reports have not been found for begonia diseases associated with phytoplasmas.

A phytoplasma representative of a new subgroup, 16SrXIII-E, associated with Papaya apical curl necrosis

Papaya apical curl necrosis (PACN) has frequently been observed in several Brazilian states. Affected plants exhibit foliar chlorosis, curvature of the apex, shortening of the internodes leading to bunching of the crown leaves, necrosis of the young apical parts, leaf drop, and dieback. Naturally infected plants were sampled and subjected to PCR assays, which confirmed that a phytoplasma was associated with the disease. Sequencing of the 16S rRNA gene, conventional and computer-simulated RFLP analyses, and phylogenetic analysis allowed the determination of the PACN phytoplasma as a representative of a new subgroup, designated 16SrXIII-E. The phytoplasmas of various 16Sr groups, including 16SrI, 16SrII, 16SrX, 16SrXII, and 16SrXVII, are known to be involved in anomalies in papaya plants in several countries. However, the present study reports, for the first time, the occurrence of a 16SrXIII phytoplasma in association with a papaya disease.

Development of Colletotrichum gloeosporioides isolated from green pepper in different culture media, temperatures, and light regimes

Control of anthracnose in green pepper involves the use of resistant varieties and/or fungicides. The selection of varieties and efficient products demands great amounts of conidia as inoculum. It is thus necessary to optimize the production of Colletotrichum gloeosporioides conidia in the laboratory, establishing the best conditions for fungus development. The present study aimed at determining the most favorable culture media, temperature, and light conditions for the production of fungus inoculum. The fungus was isolated from green pepper fruits (Capsicum annuum L.) and transferred to four culture media (PDA, oat, filtered pepper extract, and autoclaved pepper extract), under different temperatures (15, 20, 25, 30, and 35oC) and light conditions (24h dark, and 24h light). Colony growth was evaluated after 7 and 12 days of incubation. No differences were found between the culture media. However, the greatest number of conidia was obtained from colonies grown in oat medium at 25oC. Temperatures of 20 and 25oC were the most favorable for colony growth and sporulation. Higher sporulation was obtained under incubation in constant light. Cultivation of C. gloeosporioides in oat medium, at 25oC, and constant light is recommended.

Abobrinha-de-moita: um novo hospedeiro de fitoplasma do grupo 16SrIII

RESUMO Em um plantio comercial localizado no Vale do Ribeira, no estado de Sao Paulo, foram observadas plantas de abobrinha-de-moita (Cucurbita pepo L.) apresentando superbrotamento de ramos, malformacao da parte aerea e folhas disformes e enrugadas. Atraves de PCR foi demonstrada a presenca de fitoplasma associado aos tecidos doentes. Um fitoplasma do grupo 16SrIII foi identificado por PCR e pela analise de RFLP, conduzida com cinco enzimas de restricao. A presente comunicacao se constitui no primeiro relato da presenca de um fitoplasma do grupo 16SrIII em abobrinha-de-moita no Brasil. Palavras-chaves: Mollicutes, Cucurbitaceae, Cucurbita pepo, RFLP.

Caracterização molecular e patogênica de isolados de Xanthomonas albilineans (Ashby) Dowson, agente causal da escaldadura das folhas da cana-de-açúcar

ABSTRACT Leaf scald is among the five more important diseases in sugarcaneand its occurrence reduces yield and crop longevity. Resistant cultivarshave been used to control the disease, but there is evidences of theoccurrence of variants of the pathogen. In commercial fields locatedin Sao Paulo State, it has been observed that one sugarcane cultivarcan show symptoms in some regions but not in anothers, suggestingthe presence of variants within the pathogen population. Thus, theaim of this study was to investigate the presence of genetic diversityof the bacteria in commercial areas. A total of 50 isolates were obtainedin pure culture from symptomatic plants collected in ‘Piracicaba(SP)’, ‘Jau (SP)’, ‘Ribeirao Preto (SP)’ region and ‘Iturama (MG)’.The isolates were confirmed as X. albilineans by using characteristicssuch as of colony type, serology and PCR with specific primers. Rep-PCR method was used to evaluate genetic diversity using DNA Silva, M.S.; Bedendo, I.P.; Casagrande, M.V. Molecular and pathogenic characterization of isolates of

Efeito da inoculação do fitoplasma do enfezamento sobre o desenvolvimento e produção de híbridos de milho

The effect of the phytoplasma on the development and yield of ten corn (Zea mays) hybrids was evaluated. Ten-day-old plants were experimentally inoculated using ten infective insects of Dalbulus maidis/plant. Infected and healthy plants were compared regarding symptoms and yield components. Infected plants exhibited predominantly reddening of leaves, ear proliferation and stunting of different intensities. Reduction in plant height and kernel yield varied among hybrids. Reductions as high as 35% in plant height, 98% in kernel yield and number of grains/ear, 72% in ear size, 50% in number of lines/ear, and 18% in seed germination occurred in the most susceptible hybrids.