Carlos Alberto Lopes

Differential resistance of tomato cultigens to biovars I and III of Pseudomonas solanacearum

The reaction of six tomato cultigens (Yoshimatsu 4-11, Rotam-4, Rodade, Hawaii 7998, CL 1131-0-0-13-0-6, and Irat L3) to Pseudomonas solanacearum biovars I and III was evaluated in a greenhouse trial. Seedlings were root-inoculated with 11 strains of biovar I and nine strains of biovar III. The plants were individually scored 15 days after inoculation for wilt severity on a scale from 1 (no symptoms) to 5 (dead plant). Cluster analysis grouped strains of biovar III in a lower virulent cluster than those of biovar I. Yoshimatsu 4-11, Rotam-4, and Rodade had specific resistance to biovar III but not to biovar 1

Neon-S, novo meio para detecção de Sclerotinia sclerotiorum em sementes

Neon medium, originally proposed to verify the viability of sclerotia of Sclerotinia sclerotiorum, suffered modification aiming to detect the pathogen on seeds. A wide-ranged antibiotic and a form of 2,4-D acid that could withstand sterilization were incorporated in the new medium. The ideal concentration of blue bromophenol and the best light and temperature conditions for incubation of seeds on this medium were verified. All ingredients of the new medium were added before sterilization and pH adjustment was unnecessary. This medium, named Neon-S, was compared to the methods recommended for the detection pathogens on seeds by the Brazilian Ministry of Agriculture. Compared to the filter paper test and the germination paper test, the method was faster and more efficient, by reducing the detection time of the pathogen from 37 days to 12 days.

Intensidade do mofo-branco do feijoeiro em plantio convencional e direto sob diferentes lâminas d'água

A gradient of water depths, obtained with the line source irrigation system, and two bean (Phaseolus vulgaris) cultivars, under the conventional and the no-tillage cropping systems, demonstrated increases in white mold intensity caused by Sclerotinia sclerotiorum and sclerotium production with larger water depths. With an initial inoculum concentration of 0.2 sclerotia/kg of soil, the percentage of infected plants varied from 0 to 100% (1998) and from 0 to 12% (1999). A higher and more severe incidence of white mold was verified in plots planted with the cultivar of more prostrate habit, in the conventional cropping system. In both years, disease intensity, production of sclerotia and development of apothecia were lower in the no-tillage cropping system. Finally, in both experiments, about four times more sclerotia was present in the residue of grain collected from conventional tillage plots, than in the no-tillage plots, showing that the production of inoculum for the next crop is much larger in the former than in the latter. This is especially relevant, considering the importance of initial inoculum for monocyclic diseases, such as in the case of white mold, with direct implications for the sustainability of winter bean production in the dry season in Brazil.

Diversity of Brazilian biovar 2 strains of Ralstonia solanacearum

Ralstonia solanacearum is responsible for bacterial wilt disease. Specific and accurate identification of this pathogen is essential for protection of susceptible crops as well as breeding resistant varieties. Historically, R. solanacearum has been classified into biovars based on the use of sugar and alcohol as carbon sources, into races based on its ability to infect different hosts, more recently into phylotypes based on the intergenic transcribed sequence of the ribosomal RNA genes 16S and 23S and into sequevars based on the endoglucanase gene (egl) sequence. Race 3 biovar 2 (R3Bv2) is widespread in South and Central America, and in Brazil it is present in all potato-producing regions as the most prevalent strain. In this study, we classified 53 Brazilian R. solanacearum biovar 2 (Bv2) strains by traditional and molecular methods. PCR with specific primers confirmed all 53 bacterial strains as belonging to the R. solanacearum species complex, and all were classified as biovar 2A or 2T based on acidification of sugars and alcohols. Multiplex phylotype PCR assigned all strains to phylotype II. Phylogenetic analysis of egl sequences showed that most Bv2 strains from Brazil analyzed in this study did not cluster with known sequevars and are less clonal than the R3Bv2 strains reported for other countries. This is the first study to address the diversity of a collection of Brazilian R. solanacearum strains using the phylotype and sequevar classification scheme.

Uma análise do efeito do aquecimento global na produção de batata no Brasil

ABSTRACT An analysis of the potato production in Brazil upon global warming The future of the potato production in Brazil is discussed upon prediction of temperature rise due to global warming. A literature review was carried out on the effects of high temperatures on the potato plant metabolism, and their consequences upon vegetative development and yield. Although higher emphasis was devoted to the climate effect on food production, the risk of genetic erosion by disappearance of wild species is stressed, with consequences to the future of plant breeding. Based on this information and on climate data from the main growing regions published on Brazilian documents, we carried out a prospective analysis of the potato production in Brazil. For that, a temperature rise of up to 5oC was considered to the end of the century, and the range of 10oC to 25oC as the optimum for potato growth, according to specialized literature. For the study, six counties, representative of the main growing regions, were selected: Sao Joaquim, Santa Catarina State; Guarapuava, Parana State; Cristalina, Goias State; Mucuge, Bahia State; Vargem Grande do Sul, Sao Paulo State and Araxa, Minas Gerais State. For cooler counties, such as Sao Joaquim, major drawbacks on potato production are not expected, even though adjustments in planting season should be required. However, cropping on those counties subject to high temperatures which today allow potato production all year round, like Mucuge, and Cristalina, is expected to be restricted to few months of the year. The aim of this article was to alert, not alarm, the Brazilian potato chain in order to promote the management changes to preserve the crop in case the expected temperature rise comes true. In addition, the role of plant breeding to counteract the negative effects of high temperature is discussed.

Eficácia relativa de porta-enxertos comerciais de tomateiro no controle da murcha-bacteriana

A murcha-bacteriana ( Ralstonia solanacearum ) e uma das principais doencas das solanaceas em climas tropicais. Historicamente limitante a producao de tomate na Regiao Norte do Brasil, passou a ser uma seria ameaca ao tomateiro tambem nas Regioes Sul e Sudeste apos a expansao do cultivo protegido. Embora fontes de resistencia a doenca tenham sido identificadas em germoplasma de tomateiro, cultivares comerciais resistentes ainda nao estao disponiveis no mercado. O uso de porta-enxerto comerciais de tomate tem se popularizado pelo fato de reduzir o problema de incompatibilidade associada ao uso de especies/generos diferentes. O objetivo deste trabalho foi avaliar, em casa de vegetacao, os niveis de resistencia a murcha-bacteriana dos principais porta-enxertos comerciais de tomateiro, levando em conta a variabilidade patogenica de um conjunto de isolados de R. solanacearum . Foi observada uma clara distincao na incidencia da doenca entre os genotipos, porem a reacao foi do tipo isolado-dependente. Os porta-enxertos mais resistentes foram os hibridos ‘Muralha’ e ‘Guardiao’, que nao diferiram, para a maioria dos isolados, da linhagem ‘Hawaii 7996’ (padrao internacional de resistencia) e apresentaram comportamento superior em relacao aos hibridos ‘Magnet’ e ‘Protetor’. Entretanto, todos os porta-enxertos avaliados sucumbiram a alta virulencia do isolado ‘CNPH 488’ (Raca 1 / Biovar 2, coletado no Estado do Parana), que provocou a morte da totalidade das plantas. Quando avaliados em solo artificialmente infestado, com menor pressao de inoculo, ‘Guardiao’ e ‘Muralha’ apresentaram, novamente, um desempenho significativamente superior aos de outros porta-enxertos. Nossos resultados reforcam que, em condicoes ambientais favoraveis e/ou na presenca de isolados muito virulentos, dificilmente o sistema de enxertia de tomateiro em tomateiro per se protegera adequadamente a planta enxertada da murcha-bacteriana. Tal cenario exige medidas complementares e antecipadas de controle que visem a reduzir a populacao de R. solanacearum no solo ou escolha de ambiente menos propicio a sua multiplicacao.

Diversidade patogênica e molecular de Ralstonia solanacearum da região amazônica brasileira

Pathogenic and molecular diversity of Ralstonia solanacearum isolates from the Brazilian Amazon The diversity among 70 isolates of Ralstonia solanacearum collected from tomato and other hosts in the Brazilian Amazon was evaluated. Firstly, the isolates were identified at the biovar level and their virulence assessed by inoculating seedlings of tomato, sweet pepper and Amazon chicory (Eryngium foetidum). Fifty-three isolates were identified as biovar 1, four as biovar N2 and 13 as biovar 3, therefore confirming the prevalence of biovar 1 associated with tomato in the North Region of Brazil. Cluster analysis of the isolates allowed their separation into different virulence classes. On tomato, 44.3% of them were highly virulent, 37.1% were moderately virulent and 18.6% were weakly virulent. On peppers, 20% of the isolates were highly virulent, 27.1% moderately virulent and 52.9% were weakly virulent. When inoculated on Amazon chicory, only the chicory isolate caused wilt, thus revealing an uncommon specificity for R. solanacearum. Fortysix isolates from tomato and 18 from ten other hosts, collected in flooded and non-flooded areas, were then compared by BOX-PCR. Genomic fingerprints were highly polymorphic. Five groups were identified, without any clear-cut correlations among them with host of origin, biovar, ecosystem or geographic origin. The isolate obtained from Eryngium foetidum was the most divergent, with only 6.4% similarity to the other isolates. The tomato isolates were separated into three groups. All four biovar N2 isolates were grouped together and separated from the isolates representing the other biovars present in the Amazon region. Additional keywords: bacterial wilt, Lycopersicon esculentum, repetitive DNA, rep-PCR.

Powdery mildew of Allium species caused by Oidiopsis taurica in Brazil

Oidiopsis taurica Salmon (Syn. Oidiopsis sicula Scalia) was identified as the causal agent of a powdery mildew disease occurring on distinct Allium species in Brazil. This disease was initially observed in plastic house and field-grown garlic (Allium sativum) and leek (A. porrum) accessions in Brasilia (Federal District) and in field-grown and greenhouse onion (A. cepa) cultivars in Belem do Sao Francisco (Pernambuco State) and Brasilia, respectively. Typical symptoms consisted of chlorotic areas on the leaf surface corresponding to a fungal colony. These lesions turned to a brownish color with the progress of the disease. Fungi morphology was similar to that described for O. taurica. Endophytic mycelium emerging through estomata, light pale conidia were dimorphic (lanceolate primary conidia and somewhat cylindrical secondary conidia), fibrosin bodies were absent, conidia formed predominantly single (not in chains), and appressoria were non-lobed. Its sexual stage, Leveillula taurica (Lev.) Arnaud, was not observed. Inoculations were performed with the O. taurica isolates from distinct Allium hosts. These isolates were also pathogenic to sweet pepper and tomato, indicating an apparent absence of host specialization. One bunching onion (A. fistulosum) accessions was not infected by O. taurica suggesting that this species might carry useful resistance alleles to this pathogen. This is the first formal report of a powdery mildew disease on species of the genus Allium in Brazil. This disease might become important on these vegetable crops especially in hot and dry areas such as those in the Central and Northeast regions of Brazil.

BRS Ana: cultivar de batata de duplo propósito

The genotype BRS Ana is a new potato cultivar adequate for French fries, with potential for processing into frozen French fries and flakes, released in 2007. It was developed by the Embrapa Potato Breeding Program (Embrapa Temperate Agriculture, Pelotas-RS; Embrapa Transference of Technology, Office of Canoinhas-SC; and Embrapa Vegetables, Brasilia-DF), based on tuber appearance and yield, specific gravity and French fries quality. Tubers are red-skinned, lightly rough, oval shaped with shallow eyes. The pulp is white. Cultivar BRS Ana has high yield potential. In the subtropical ecosystem, cultivar BRS Ana showed higher yield (31.2 t ha-1) than the most used cultivars in Brazil when grown in autumn, and did not differ from them in the spring. In the tropical ecosystem, under irrigation, BRS Ana did not differ from both control cultivars. It produced higher percentage of marketable tubers (55.6%) and average tuber weight (108.4 g) than the controls in the fall crop of subtropical ecosystem. In both ecosystems, cultivar BRS Ana presented high specific gravity (1.086) and dry matter content (19.7%). The sensorial analysis showed that cultivar BRS Ana is adequate for home made French fries as well as for industrial processing. It is moderately susceptible to late blight (Phytophthora infestans) and presents good resistance to early blight (Alternaria solani). The reaction to the tuber soft rot (Pectobacterium sp.) is similar to the most used cultivars. It has low seed degeneration conferred by moderate resistance to PVY and low incidence of PLRV. Susceptibility to tuber physiological disorders has not been observed. It seems that BRS Ana has lower fertilizer and water requirements than the most planted cultivars, meaning reduction of crop cost and risk. In the subtropical ecosystem, tuberization starts later in spring, therefore BRS Ana should be planted earlier in the season.

Efeito da solarização e biofumigação na incidência da murcha bacteriana em tomateiro no campo

Effect of soil solarization and biofumigation on tomato bacterial wilt incidence. Soilborne plant pathogens cause heavy losses to many vegetable crops. Solarization and organic residues amendments have been evaluated as disease control strategies with good perspectives for aplication in integrated management. Field experiments were carried out at Embrapa Hortalicas, Brasilia-DF, to evaluate the effects of amending soil with organic residues (biofumigation) and solarization on the incidence of bacterial wilt (Ralstonia solanacearum) on tomato, on soil chemical characteristics, and weed control. Amendments with brassica residues (2%), chicken litter residues (2%), methyl bromide treatments and no soil treatment, with or without soil solarization were evaluated. After solarization and biofumigation, soil samples were collected for chemical analysis and weed seed bank evaluation. The tomato seedlings were transplanted after two months of soil solarization. Soil solarization reduced soil pH and levels of B and Zn. Organic amendments increased levels of Ca, K and Na and reduced levels of Al. Soil solarization reduced the number of weed seeds in the soil, mainly monocotyledons. Methyl bromide treatments and chicken litter amendments significantly reduced bacterial wilt incidence and disease progress.