Armando Bergamin Filho

Yield loss caused by huanglongbing in different sweet orange cultivars in São Paulo, Brazil

Citrus huanglongbing (HLB) reduces an affected orchard’s economic life. This work aimed to characterize yield loss due to HLB for different sweet orange cultivars and determine the relationship between disease severity and yield. Disease severity and yield were assessed on 949 individual trees distributed in 11 different blocks from sweet orange cultivars Hamlin, Westin, Pera and Valencia. In each block, plants showing a range of HLB severity levels and asymptomatic plants were selected. Total yield (weight of harvested fruit), mean weight of asymptomatic and symptomatic fruit, relative yield (symptomatic tree yield/mean yield of asymptomatic trees from the same block) and relative number of fruits (fruit number from symptomatic tree/mean number of fruits from asymptomatic trees from the same block) were determined. The weight of symptomatic fruit was lower than the weight of asymptomatic fruit, but the weights of asymptomatic and symptomatic fruit were not correlated with disease severity, indicating that the effects of HLB were restricted to symptomatic branches. The relationship of the relative yield with HLB severity can be satisfactorily described by a negative exponential model. The rates of yield decrease as a function of disease severity were similar for all assessed cultivars. A relative yield (up to 19%) was observed even for trees where disease severity was 100%. The strong linear relationship between relative number of fruits per tree and the relative yield per tree suggested that the yield reduction was due primarily to early fruit drop or lack of fruit set on affected branches.

Base científica para a erradicação de plantas sintomáticas e assintomáticas de Huanglongbing (HLB, Greening) visando o controle efetivo da doença

Instituto Agronomico do Parana - IAPAR, 86001-970, Londrina, PR, BrasilAutor para correspondencia: Jose Belasque Junior, e-mail: belasque@fundecitrus.com.br1. IntroducaoHuanglongbing (HLB), ou Greening, e a doenca mais importante e destrutiva da citricultura mundial (Bove, 2006; Gottwald et al., 2007a). Presente de forma endemica nos continentes asiatico e africano ha varias decadas, essa doenca foi recentemente detectada nos dois principais paises produtores de citros, Brasil e Estados Unidos (Colleta Filho et al., 2004; Halbert, 2005; Teixeira et al., 2005). O Brasil detem 30% da producao mundial de laranja e 59% da producao de suco de laranja (Neves et al., 2007). Sao Paulo e Florida dominam a oferta mundial, um caso raro em se tratando de commodities agricolas. O sistema agroindustrial citricola brasileiro movimenta anualmente R

Transgenic Sweet Orange (Citrus sinensis L. Osbeck) Expressing the attacin A Gene for Resistance to Xanthomonas citri subsp. citri

9 bilhoes e gera mais de 400 mil empregos diretos e indiretos. Pelos danos que causa e pela dificuldade do seu manejo, o HLB coloca em risco esse importante setor do agronegocio brasileiro. Ha necessidade de acoes conjuntas urgentes envolvendo citricultores, industrias processadoras e os governos federal e estaduais. Em 17 de Outubro de 2008 entrou em vigor a Instrucao Normativa n

Injuries caused by citrus leafminer (Phyllocnistis citrella) exacerbate citrus canker (Xanthomonas axonopodis pv. citri) infection

Genetic transformation with genes that code for antimicrobial peptides has been an important strategy used to control bacterial diseases in fruit crops, including apples, pears, and citrus. Asian citrus canker (ACC) caused by Xanthomonas citri subsp. citri Schaad et al. (Xcc) is a very destructive disease, which affects the citrus industry in most citrus-producing areas of the world. Here, we report the production of genetically transformed Natal, Pera, and Valencia sweet orange cultivars (Citrus sinensis L. Osbeck) with the insect-derived attacin A (attA) gene and the evaluation of the transgenic plants for resistance to Xcc. Agrobacterium tumefaciens Smith and Towns-mediated genetic transformation experiments involving these cultivars led to the regeneration of 23 different lines. Genetically transformed plants were identified by polymerase chain reaction, and transgene integration was confirmed by Southern blot analyses. Transcription of attA gene was detected by Northern blot analysis in all plants, except for one Natal sweet orange transformation event. Transgenic lines were multiplied by grafting onto Rangpur lime rootstock plants (Citrus limonia Osbeck) and spray-inoculated with an Xcc suspension (106xa0cfuxa0mL−1). Experiments were repeated three times in a completely randomized design with seven to ten replicates. Disease severity was determined in all transgenic lines and in the control (non-transgenic) plants 30xa0days after inoculation. Four transgenic lines of Valencia sweet orange showed a significant reduction in disease severity caused by Xcc. These reductions ranged from 58.3% to 77.8%, corresponding to only 0.16–0.30% of leaf diseased area as opposed to 0.72% on control plants. One transgenic line of Natal sweet orange was significantly more resistant to Xcc, with a reduction of 45.2% comparing to the control plants, with only 0.14% of leaf diseased area. Genetically transformed Pera sweet orange plants expressing attA gene did not show a significant enhanced resistance to Xcc, probably due to its genetic background, which is naturally more resistant to this pathogen. The potential effect of attacin A antimicrobial peptide to control ACC may be related to the genetic background of each sweet orange cultivar regarding their natural resistance to the pathogen.

Natural infection of Nicandra physaloides by Tomato severe rugose virus in Brazil.

After the introduction of citrus leafminer in Sao Paulo State, an increase in the number of new plants infected with citrus canker has been observed. The interaction between these two organisms is known, but there is no information about how the leafminer damage intensifies citrus canker incidence and severity. The objectives of this paper were to evaluate the effects of leafminer damage in citrus canker infection and its influence on the monocyclic components of the disease on Citrus limonia. Higher incidence of diseased plants, AUDPC (area under the disease progress curve), disease severity and shorter incubation periods were observed in plants inoculated after insect infestation. These factors explain the association found between the higher citrus canker intensity and the damage caused by the insect and show, albeit partially, the consequences of these changes in the spread of the pathogen under natural conditions of infection.

Dinâmica Temporal da Clorose Variegada dos Citros em Três Regiões do Estado de São Paulo

Nicandra physaloides, a common weed in South America, was found to be infected by an isolate of Tomato severe rugose virus (ToSRV), a bipartite begomovirus. The plants developed severe yellow rugose mosaic and were collected in São Paulo State, Brazil. This isolate of ToSRV was transmitted by Bemisia tabaci B biotype from infected plants of N. physaloides to healthy plants of N. physaloides and tomato in a glasshouse. This is the first report of natural infection of N. physaloides by ToSRV in Brazil.

Doenças com período de incubação variável em função da fenologia do hospedeiro

CVC is considered the most important disease of brazilian citrus industry but many aspects of its epidemiology are still unknown. This work aimed to characterize the spatial pattern of CVC affected trees in three regions (Northwest, Center and South) of Sao Paulo state, Brazil. Three orchards of Pera sweet orange (Citrus sinensis) grafted on Rangpur lime (Citrus limonia) were evaluated twice a month by visual assessments from July 1998 to December 2000. For each evaluation all plants were inspected and assigned as diseased or healthy and cumulative maps were produced. The following analyses were performed: ordinary runs, isopath areas, Taylor law, dispersion index and foci structure and dynamics analysis. Ordinary runs indicated a trend to randomness. Isopath areas analysis showed few compact foci and a trend to uniform incidence in all areas. The other analysis showed few if any differences between regions and results that could classify CVC pattern as slightly aggregated.

Prováveis consequências do abrandamento da metodologia de erradicação do cancro cítrico no Estado de São Paulo

Um periodo de incubacao de cinco dias significa, no contexto da epidemiologia de doencas de plantas, que as infeccoes que deram origem aos sintomas visualizados no tempo t ocorreram no tempo t-5. Ha um grupo de doencas, no entanto, que se comporta de modo diferente, isto e, o momento da infeccao nao pode ser inferido a partir da visualizacao dos sintomas. Esse grupo de doencas pode ser dividido, para fins didaticos, em funcao do orgao da planta que exibe os sintomas: (i) brotacoes jovens; (ii) perfilhos jovens; (iii) frutos recem-amadurecidos. Nesses tres subgrupos, a expressao dos sintomas e funcao do estadio fenologico do orgao afetado e tem pouca relacao com o momento da infeccao. Para essas doencas, maior enfase e recomendada para estudos que visem a identificacao da epoca mais provavel de ocorrencia da infeccao, em detrimento do simples acompanhamento da expressao dos sintomas. Exemplos sao apresentados para cada subgrupo e o modelo de crescimento monomolecular e sugerido como o que melhor descreve o progresso da doenca em funcao do tempo para o grupo como um todo.

Incidência e severidade de cancro cítrico em laranja 'Pêra Rio' sob condições de controle químico e proteção com quebra-vento

Recentemente a Secretaria de Agricultura e Abastecimento do estado de Sao Paulo abrandou os criterios relacionados a erradicacao do cancro citrico. Em abril de 2009 mais de 99,8% dos talhoes comerciais de laranjeiras doces estavam livres da doenca em Sao Paulo. Abrandar a metodologia de erradicacao significa comprometer esse elevado nivel de sanidade dos pomares e a competitividade da citricultura, com reflexos negativos financeiros e ambientais. Diante desses fatos sugere-se: a) que a erradicacao da doenca volte a ser feita como anteriormente utilizada; ou b) a adocao de uma nova metodologia de erradicacao, mais efetiva na supressao da doenca, quando em novos levantamentos amostrais de cancro citrico em Sao Paulo forem encontradas incidencias de talhoes comerciais com a doenca superiores a 0,36%. Essa incidencia foi calculada comparando-se pelo teste de Duncan (P<0,05) os levantamentos amostrais de cancro citrico realizados de 1999 a 2009. A diferenca minima significativa encontrada foi de 0,28. A menor incidencia do cancro citrico em Sao Paulo foi de 0,08%, observada em 2001. Dessa forma, como alternativa, propoe-se a adocao de uma metodologia mais drastica de erradicacao do cancro citrico quando em um novo levantamento amostral for detectado mais que 0,36% de talhoes comerciais com cancro citrico.

Alterações na fotossíntese e na transpiração de folhas de milho infetadas por Phaeosphaeria maydis

The objective of this work was to study citrus canker incidence and severity under natural conditions in an orchard of Pera Rio sweet orange planted in Ourizona county, northwest of Parana State, Brazil. Chemical control, by using copper sprays, and windbreak protection were evaluated to reduce citrus canker incidence and severity on leaves. Levels of disease incidence were determined monthly by rating diseased leaves. Severity was evaluated monthly by using specific diagrammatic scales. Levels of severity were calculated considering just the diseased leaves assessed. Data were plotted on temporal progress curves and analyzed regarding the standardized area under disease progress curve (AUDPC*). The coefficient of determination (R2) between incidence and severity levels was also determined. Whereas copper sprays significantly reduced citrus canker on leaves, windbreak did not contribute significantly to disease control. After 29 assessments, plants submitted to frequent copper sprays showed AUDPC* values for citrus canker incidence 43.5% lower than those observed on plants not protected with chemical sprays. The same result was observed for citrus canker severity. After 18 assessments, plants sprayed with copper showed AUDPC* values for severity 37.1% lower than for check plants. In both years, the values of R2 between incidence and severity levels were higher than 0.80 (p<0.01).