Rui Pereira Leite Júnior

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

Detecção de Xylella fastidiosa em germoplasma de cafeeiro

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

Agronomic performance of Pera and related sweet orange accessions naturally infected with Citrus tristeza virus in northern Paraná State, Brazil

The bacterium Xylella fastidiosa has a large host range, including species of 28 different mono and dicotiledoneous plant families. On coffee (Coffea spp.), X. fastidiosa was previously reported only on the species Coffea arabica. Studies were carried out to determine the presence of X. fastidiosa in different species and interspecific hybrids of coffee. The species of coffee included in this study were the following: C. kapakata, C. canephora, C. racemosa, C. arabica, C. dewevrei, C. stenophylla and C. eugenioides. The interespecific hybrids of C. arabica examined were the following: C. arabica x C. dewevrei, C. arabica x C. eugenioides, C. arabica x C. racemosa and C. arabica x C. robusta. Samples were collected from plagiotropic branches of different plants for each species or hybrid. Four replicates were examined for each coffee accession examined. Detection of X. fastidiosa in the samples was determined by DAS-ELISA and indirect immunofluorescence. The bacterium was detected in all seven species and four hybrids of coffee studied. However, the plants did not show any symptom of infection by X. fastidiosa. The species C. arabica showed the highest proportion of positive samples and the largest absorbance values in the DAS-ELISA test. In contrast, the species C. racemosa and C. dewevrei showed the lowest proportion of positive samples for the presence of X. fastidiosa, as well as, the lowest absorbance values in the DAS-ELISA test.

Sensibilidade de Xanthomonas axonopodis pv. citri ao cobre e mancozeb

Despite of the susceptibility to the Citrus tristeza virus (CTV), Pera sweet orange is the most important citrus cultivar in Brazil. The objective of this study was to evaluate the CTV aggressiveness and the relationship with the agronomic performance of 24 accessions of Pera and related sweet oranges. Accessions belonging to the Citrus Germplasm Collection of the Instituto Agronomico do Parana (IAPAR), Londrina, PR, were included in the study. Citrus tristeza disease was rated based on the severity of stem pitting symptoms. Yields were evaluated in the 2010/2011, 2011/2012, and 2012/2013 seasons, and tree growth in 2012. The best performance regarding stem pitting severity was shown by Redonda accession, followed by Ipigua II. Vegetative tree vigor was more evident for Redonda, Tardia CO3, and Guilherme Spagnol accessions. These Pera and related sweet oranges accessions also showed the highest fruit yields, along with Vimusa, Santa Tereza, Ipigua, Ipigua II, D-6, and Paulo Rosa. Vegetative tree vigor, yield and number of fruits were inversely correlated with citrus tristeza disease stem pitting severity. Therefore, the poor agronomic performance of some Pera and related sweet oranges is probably related to the presence of severe CTV complexes infecting these accessions.

Seqüenciamento e Variabilidade do Fragmento Genômico de Xylella fastidiosa Amplificado pelos Iniciadores RST31/33*

Citrus canker, caused by Xanthomonas axonopodis pv. citri (Hasse) Vauterin et al. 1995 (Xac), is one of the most important problems for citrus production around the world. Spraying with copper compounds is a major measure for control of the disease. The objective of this study was to determine the sensitivity of Xac strains from the State of Parana, Brazil, to copper as well as to a mixture of copper with mancozeb. The highest copper concentration where Xac grew was 50 µg/mL. However, 45.5 % of the bacterial strains from orchards with regular sprays of copper compounds grew in the presence of 50 µg/mL of copper. In contrast, only 13.4 % of the strains from citrus orchards that never received copper sprays grew in such a copper concentration . Mixing mancozeb with copper increased the tolerance of Xac to copper. Therefore, the recommendation of mancozeb mixed with copper for control of the citrus canker bacterium should be reviewed.

Citrus tristeza disease severity and agronomic performance of ‘Pêra’ sweet orange cultivars and selections in the North and Northwest regions of the State of Paraná, Brazil

Xylella fastidiosa causes several plant diseases of economic importance such as citrus (Citrus spp.) variegated chlorosis (CVC), Pierces disease of grapevine (Vitis vinifera) and leaf scorch of plum (Prunus salicina) and coffee (Coffea arabica). The nucleotide sequence of the genomic fragment, specific to Xylella fastidosa, amplified by the pair of primers RST 31/33, was determined for 38 isolates from citrus and for isolates from grapevine, coffee and plum in order to assess the level of sequence polymorphism of this fragment among isolates, as well as its genomic identity. Sequence polymorphism was not observed among isolates from citrus, but was detected among isolates from citrus and from grapevine, coffee and plum. The presence of a RsaI restriction site, which distinguishes isolates from citrus and grapevine from plum and other arboreal species, was identified in a North American isolate from plum but not in a Brazilian one.

Severity and genetic diversity of Citrus tristeza virus complexes infecting ‘Pêra Bianchi’ sweet orange in Paraná, Brazil

‘Pera’ sweet orange is the most important citrus cultivar in Brazil, but it is highly susceptible to Citrus tristeza virus (CTV), the causal agent of citrus tristeza disease. In this study, we evaluated the severity of citrus tristeza disease and its relation with the agronomic performance of seven cultivars and six selections of ‘Pera’ sweet orange under field conditions in the North and Northwest regions of the State of Parana, Brazil. The citrus tristeza disease severity was determined based on symptoms of stem pitting. The vegetative growth assessed in trees of all four locations for the 2012 season, and in two field plots for the 2011, 2012 and 2013 harvests, respectively. The cultivar ‘IPR 153’ (Bianchi) had the best performance concerning stem pitting severity, while Selection 27 was among the ones with the highest rate of vegetative growth. Further, Selections 27 and 12, and the cultivar ‘Vimusa’ had the largest fruit yields. Based on correlation analysis, stem pitting symptoms severity was negatively correlated with vegetative growth and fruit yield. Furthermore, environmental conditions may have played an important role in the severity of citrus tristeza disease and consequently on the agronomic performance of the cultivars and selections of ‘Pera’ sweet orange in the North and Northwest regions of the State of Parana.

Low-molecular-weight metabolites produced by Pseudomonas aeruginosa as an alternative to control Huanglongbing in Citrus sinensis cv. Valencia

The aggressiveness and genetic diversity of the Citrus tristeza virus (CTV) infecting sweet orange ‘Pêra Bianchi’ (Citrus sinensis) trees were evaluated under the environmental conditions of the state of Paraná, Brazil. Disease severity was assessed based on stem pitting symptoms in the citrus trees, while genetic diversity was determined by sequencing the virus coat protein (CP) gene. Stem pitting symptoms were less severe in trees maintained under greenhouse conditions and field experimental plots in the municipalities of Paranavaí and Umuarama, where the temperature is higher. In contrast, the most severe stem pitting symptoms were observed in trees from experimental orchards established in colder areas (i.e. municipalities of Arapongas, Cascavel and Londrina), suggesting a temperature effect on symptom development. Analysis of CP sequences indicated intra- and interspecific diversity of the CTV complex for most of the trees included in this study. Recombination analyses of the CP gene also allowed to identify recombinants with parentals related to PIAC-5, a mild isolate, and 1BL-3, found in trees from a field plot in Londrina. The CTV complex infecting ‘Pêra Bianchi’ trees under field conditions showed a high degree of genetic diversity, implying the possibility of multiple infections or even a dynamic rearrangement of the genotypes into different CTV complexes under the environmental conditions of the state of Paraná.

Performance of ‘Cadenera’ orange trees grafted on five rootstocks

Huanglongbing (HLB) is the most destructive disease of citrus worldwide and an efficient management strategy to control it has not yet been established. The potential of pseudomonads to suppress plant pathogens is well known and the secondary metabolites they produce represent new alternatives of compounds to control plant diseases. The main challenge is to find new compounds that show strong antibiotic activity, low toxicity to plants and little or no harm to the environment. The objectives of the present study were to determine the potential of the F4A fraction from Pseudomonas aeruginosa to control HLB and to induce systemic resistance. Low molecular weight compounds with antimicrobial activity were purified with organic solvent, thin layer chromatography (TLC) and normal and reverse phase chromatography. Compounds present in the F4A fraction were mainly obtained by thin-layer chromatography (TLC) and Preparative-High Performance Liquid Chromatography (HPLC-prep). To assess their biological activities, conventional and quantitative polymerase chain reaction were usxed. The F4A was sprayed on citrus trees infected with the causal agent of HLB, ‘Candidatus Liberibacter asiaticus’ under greenhouse conditions. The bacterial titers were reduced and defense genes were induced in leaves of trees treated with F4A, as assed by PCR analysis. The results showed that F4A (pseudomonads secondary metabolites) may provide a useful tool for the management of HLB.

‘JAFFA’ SWEET ORANGE PLANTS GRAFTED ONTO FIVE ROOTSTOCKS

Citriculture is an important alternative for the agribusiness development in the state of Paraná, Brazil. However, the use of a few cultivars of scion and rootstock restricts the harvest period and increases the vulnerability to pests and diseases. This study aimed to evaluate the vegetative growth, production and fruit quality of ‘Cadenera’ orange trees (Citrus sinensis (L.) Osbeck ) grafted on five rootstocks, during nine harvests, under a subtropical environmental condition. The experimental design was randomized blocks with six replications, two plants per plot, and five rootstocks: ‘Rangpur’ lime (C. limonia Osb.), ‘Cleopatra’ (C. reshni hort. ex Tanaka ) and ‘Sunki’ mandarins (C. sunki hort. ex Tanaka (L.) Raf.), ‘Swingle’ citrumelo [C. paradisi Macfad. x Poncirus trifoliata (L.) Raf.], and ‘C-13’ citrange [C. sinensis (L.) Osbeck cv. Pera x P.s trifoliata (L.) Raf.]. Biometric variables, and fruit yield and quality were analyzed. The smallest canopy size was induced by ‘Rangpur’ lime and ‘C 13’ citrange rootstocks. ‘Swingle’ citrumelo and ‘C 13’ citrange provided the highest yields for the ‘Cadenera’ sweet orange trees and were superior to ‘Rangpur’ lime. Trees grafted on ‘C 13’ citrange presented the highest yield and productive efficiency.