Carlos Hidemi Uesugi

Caracterização morfocultural e molecular de isolados de Colletotrichum gloeosporioides patogênicos ao mamoeiro

Twenty-nine monoconidial cultures of Colletotrichum isolated from papaya (Carica papaya) petioles and fruits were characterized by conidial and appressoria morphology, colony color, growth rate, sensitivity to benomyl, presence of setae, presence of the teleomorph, PCR with taxon-specific primers and analysis of PCR-RFLP of the ITS region. The 29 isolates from papaya were identified as C. gloeosporioides, based mainly on conidial and appressoria morphology, with most isolates producing cylindrical and/or obclavate conidia and entirely or weakly lobed appressoria, in contrast with the strawberry (Fragaria x ananassa) isolate of C. acutatum, which produced fusiform conidia and circular appressoria with entire edges. Presence of setae, teleomorphic stage, colony color, sensitivity to benomyl and growth rate were variable among isolates and influenced by the culture medium. All papaya isolates and four isolates (C. gloeosporioides and C. acutatum) from other hosts, mango (Mangifera indica), strawberry and apple (Malus domestica), were pathogenic to papaya fruits cv. Sunrise Solo, producing similar symptoms, but with variability in aggressiveness. PCR with C. gloeosporioides-specific primer, CgInt, confirmed the identity of four papaya isolates. Two other isolates reacted with C. acutatum-specific primer, CaInt2. The majority of papaya isolates (23), however, did not react with any of the primers tested. In contrast, RFLP analysis of the amplified ITS region with RsaI, generated distinct patterns that could differentiate between the two species, C. gloeosporioides and C. acutatum, and showed uniformity among papaya isolates.

Colonização de raízes de plantas daninhas cultivadas in vitro e em vasos por Ralstonia solanacearum, biovares 1, 2 e 3

The colonization of weed roots by strains of biovars 1, 2 and 3 of Ralstonia solanacearum was evaluated in vitro and in greenhouse conditions. In vitro, seed dormancy was broken, disinfested and sown in modified Murashige & Skoog (MS) culture medium in test tubes. The bacteria were inoculated by transferring a portion of the mass on the MS medium adjacent to the seedlings. Root colonization was evaluated visually, according to the concentration of bacteria around and along the length of the roots and compared with a diagram scale with scores ranging from 1 to 4. The area under the curve of root colonization (AUCRC) was calculated and analyzed. In the greenhouse, populations of six variants of the same biovars were quantified from the roots of the weeds. Plants were inoculated without wounding the roots, by pouring 100 ml of bacterial suspension (108 cfu/ml) per pot. Evaluation was done 35 days after inoculation, by plating diluted root extracts and counting the colonies. In the plants species studied, different symptoms and root colonization levels by the bacteria were observed. Although the two methods yielded similar results, the in vitro technique is promising as an auxiliary method of evaluation for root colonization of large numbers of botanic species by different strains of R. solanacearum.

Control of Post-harvest Anthracnose Infection in Guava (Psidium guajava) Fruits with Phosphites, Calcium Chloride, Acetyl Salicylic Acid, Hot Water, and 1-MCP

The control of anthracnose (Colletotrichum simmondsii) during the post-harvest stage in guava fruits (Psidium guajava L.) was performed by the application of phosphites [phosphite-K (40% P2O5 and 30% K2O) and phosphite-Ca (10.7% P2O5, 3.89% Ca, and 0.5% B)] including the Carbendazim as reference, calcium chloride (CaCl2), acetyl salicylic acid (ASA), hot water (HW), and 1-methylcyclopropene (1-MCP). These treatments were applied individually or in combination each other with two or three compounds. The evaluated parameters were diameter of anthracnose lesion (DL), number of lesions (NL), and fruit quality (fresh weight loss, pH, total soluble solids, and titrable acidity]. The fruits were disinfested, inoculated, and maintained in an incubator containing fluorescent lights at 75 µmol·m-2·s-1 (25°C, 12h photoperiod) for 5 days and were then analyzed. The results showed that the DL and the NL were reduced following treatments, and that the HW (47°C for 20 min) was the strongest and the 1-MCP treatment was the least effective. The physico-chemical characteristics of fruits were affected by some treatments without compromising fruit quality. The combination of treatments was also able to alleviate the anthracnose effect on fruits compared to individual treatments and the control without affect the fruit quality. The combinations which included the HW treatment showed the best performance to control this disease, particularly when combined with the 1-MCP and phosphite.

Desempenho agronômico de maracujazeiros tratados com produtos alternativos e fertilizantes foliares

ABSTRACT – Induced resistance is an alternative method to control of plants diseases. However, there are few studies relating the effect of these products and methods to the plants yield, and to the physical and chemical fruit characteristics. This study was carried out to evaluate diseases severity, fruits physical and chemical characteristics, and yield of passion fruits plants treated with alternative products and foliar fertilizers. Cloned plants of passion fruit cultivar ‘BRS Gigante Amarelo’ were sprayed at each fifteen days, during one year with water (control), Cuprozeb ® (standard fungicide), acibenzolar-S-metil - ASM, Agro-mos ® , potassium phosphite, fosetyl-Al, gypsun and CPAC-GE (product in test). Experimental design was randomized blocks with four repetitions and twenty fruits per repetition. For the yield analysis were utilized four repetitions and six plants per plot. Harvestings of fruits were made from November, 2008 to April, 2009. For analyzing the disease severities was utilized a diagrammatical grade scale. All products were efficient in reducing the severity of woodiness virus, fruit-scab and bacteriosis, excepting the Cuprozeb

Sensitivity to copper in Xanthomonas campestris pv. viticola

O cancro bacteriano, causado por Xanthomonas campestris pv. viticola, afeta o cultivo irrigado de videira no Vale do Submedio Sao Francisco, nos estados de Pernambuco e Bahia. O manejo da doenca tem sido realizado atraves de um conjunto de praticas que inclui a aplicacao de cupricos. Este tem sido o unico metodo de controle quimico disponivel e o mais utilizado nas areas de ocorrencia da doenca. O objetivo deste estudo foi avaliar a sensibilidade ao cobre de estirpes de X. campestris pv. viticola coletadas em diferentes localidades, entre os anos de 1998 a 2006. Detectou-se variabilidade na sensibilidade ao oxicloreto de cobre e ao sulfato de cobre entre as 21 estirpes testadas. A concentracao minima inibitoria variou entre 10 e 60 µg/mL Cu2+, para os dois produtos. De forma geral, observouse uma evolucao no crescimento da tolerância ao cobre ao longo dos anos, com as estirpes brasileiras apresentando maior tolerância que a estirpe-tipo, coletada em 1972 na India. As diferencas observadas em sensibilidade ao cobre entre as estirpes de X. campestris pv. viticola podem levar, com o uso continuo de compostos cupricos na regiao, a selecao e dominância das estirpes mais tolerantes na populacao bacteriana.

Tratamentos térmico e químico de sementes de feijoeiro: eficiência na erradicação de Curtobacterium flaccumfaciens pv. flaccumfaciens e efeitos na qualidade fisiológica das sementes

The effect of thermo and chemotherapy on the eradication of Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) and on the physiological quality of seeds of common bean (Phaseolus vulgaris) cv. Perola were tested. Soaking times (30 min, 1 and 2 h) in water and in AGRIMAICIN 500 solutions (copper sulphate, 500 g + oxytetracyclin, 30 g/kg of the product) in concentrations of 5 and 10 g/L of water; dry heat (60 and 70 oC for 1, 2, 3, 6 and 12 h); and heat of 60 oC/3 h on previously soaked seeds for 30 min, 1 and 2 h were tested. The vigor of seeds soaked in water for more than 1 h was affected. Soaking the seeds (30 min, 1 and 2 h) in solution with 10 g of AGRIMAICIN 500/L of water affected the length of the rootlet and the stem, whereas germination was affected only with 2 h. The treatment eliminated the bacterium from naturally infected seeds; however it was not effective in inoculated seeds (108 ufc/mL). Dry heat (60 and 70 oC) for more than 3 h reduced significantly the vigor of the seeds and did not eliminate the bacterium. Soaking the seeds for 30 min and 1 h + 60 oC/3 h affected the length of the stem and rootlet but did not eliminate the bacterium. Two hours of soaking the seeds in water ± 60 oC/3 h reduced significantly the germination and the vigor; it also reduced significantly the Cff in inoculated seeds, whereas it eliminated the bacterium in naturally infected ones.

Colonização radicular de plantas cultivadas por Ralstonia solanacearum biovares 1, 2 e 3

Bacterial wilt caused by Ralstonia solanacearum is considered the main plant disease of bacterial origin in the world, where hundreds of plant species in more than 50 botanical families are host plants. Root colonization of lettuce (Lactuca sativa), rice (Oryza sativa), spring onion (Allium fistulosum), pea (Pisum sativum), cucumber (Cucumis sativus), and soybean (Glycine max) by six isolates of Ralstonia solanacearum (Rs) biovars 1, 2 and 3 was evaluated under greenhouse conditions. Bacterial strains resistant to streptomycin, rifampicin and chloranfenicol were used. Root colonization was evaluated 45 days after inoculation by counting bacteria in root extracts of culture media with antibiotics. Pea plants hosted all six isolates, but only the isolate biovar 3 was pathogenic to this species. High populations of four isolates of the three biovars were found on soybean, and cucumber hosted high population of only two isolates (biovars 1 and 3). Pea was a non-susceptible host for Rs, except for one pathogenic isolate. Rice hosted very low populations of all isolates, while lettuce and spring onion did not host any isolates. These results showed the ability of Rs to colonize and survive on different plant roots as rhizobacteria.

Virulência de estirpes (biovar 1 e 2T) de Ralstonia solanaceraum a Eucalyptus spp.

The bacterial wilt of Eucalyptus (Ralstonia solanacearum Race 3 biovar 2T) was reported in field of Eucalyptus hybrid urograndis. The objective of this research was to evaluate the virulence of two R. solanacearum strains to 17 Eucalyptus species, using the seed microbiolization method for pathogen inoculation. The results of the statistical analyses showed that virulence varied between the two R. solanacearum strains. The R3bv2T virulence was higher than the one in R1bv1 in the following Eucalyptus species: urograndis, E. urophylla, E. grandis x E. camaldulensis, E. grandis, E. microcorys, E. deanei, and E. phaeotricha. The virulence of the R1bv1 strain was higher only in E. pellita. Among species of Eucalyptus the following ones were more susceptibles: to R3bv2T strain - urograndis, E. grandis and E. paniculata, and to R1bv1 strain - E. cloeziana, E. paniculata, E. botryoides, E. pellita, E. propinqua and E. resinifera.

Ocorrência de murcha bacteriana em helicônias e musácea ornamental no Distrito Federal

Plantas de Heliconia spp. e Musa spp. apresentando murcha foram observadas em plantio comercial no Distrito Federal. Testes laboratoriais e de inoculacao confirmaram como sendo a bacteria Ralstonia solanacearum biovar 1 raca 2 responsavel pela doenca. Este e o primeiro relato da presenca da bacteria em heliconia e musacea ornamental na regiao.

Bactérias extremófilas facultativas melhorando a germinabilidade de sementes de Eucalyptus urophylla S.T. blake

In this study the effect of seed microbiolization with facultative extremophile bacteria (Bacillus sp. and Enterobacter sp.), isolated in previous work, from extreme conditions of pH and NaCl and able to increase eucalyptus phytomass, on seed germinability of Eucalyptus urophylla S.T. Blake was evaluated. Mean germination time, speed of germination and coefficient of speed germination were measured to evaluate germinability. The experiment was conducted in a completely randomized design including 11 treatments (five strains of Bacillus sp., five of Enterobacter sp. and one control without bacteria), formed by 8 replicates with 25 seeds each. The results showed that Bacillus sp. strains UnB 1366 and UnB 1374 significantly reduced the lower mean germination time and higher coefficients and speed of germination in relation to the other strains.