ABSTRACT. Bacterial leaf streak caused by Xanthomonas vasicola pv. vasculorum is an emerging disease for corn production around the world. However, information on management of this disease is still limited. This study aimed to determine the in vitro sensibility of X. vasicola pv. vasculorum to different chemicals and to evaluate the control of bacterial leaf streak on corn under greenhouse conditions. In vitro tests were carried out with kasugamycin, copper sulfate, copper oxychloride, copper hydroxide, cuprous oxide, bioactive copper, mancozeb, chlorothalonil, methyl thiophanate, and tebuconazole at the dosages of 1, 5, 10, 20, 50, 100, 200, and 400 μg mL−1. Four strains of X. vasicola pv. vasculorum were included in the study. The minimal inhibitory concentration for kasugamycin ranged from 50 to 200 μg mL-1, whereas to the inorganic copper compounds varied from 5 to 50 μg mL-1 and to the bioactive copper was 100 μg mL-1. Further, mancozeb and tebuconazole inhibited the bacterial growth at the dosage ranging from 5 to 20 μg mL-1 and 50 to 400 μg mL-1, respectively, depending on the X. vasicola pv. vasculorum strain. Chlorothalonil and methyl thiophanate did not inhibit the growth of the bacterium at any tested concentration. The control of bacterial leaf streak under greenhouse conditions was investigated on corn plants of the cultivar IPR 164 at the V3 phenological vegetative stage, sprayed with kasugamycin (3 mL L-1), copper oxychloride (1.5 mL L-1), bioactive copper (1 mL L-1), mancozeb (2 g L-1), tebuconazole (1 mL L-1), and chlorothalonil (2 mL L-1). The corn plants were inoculated with a 108 CFU mL-1 suspension of the RL1 strain of X. vasicola pv. vasculorum. Only copper oxychloride significantly reduced disease severity. However, this copper compound caused phytotoxicity to the corn plants at the tested concentration.

Resumo Estudos sobre porta-enxertos e copas têm grande importância para a produção de citros. O objetivo do estudo foi avaliar o crescimento vegetativo, a produção das plantas e a qualidade dos frutos de laranja ‘Navelina’ enxertadas sobre cinco porta-enxertos na região Norte do Paraná, Brasil. O delineamento experimental foi de blocos ao acaso, com seis repetições, duas plantas por parcela e cinco tratamentos: limão ‘Cravo’; tangerina ‘Cleópatra’; tangerina ‘Sunki’, citrumelo ‘Swingle’ e citrange ‘Fepagro C-13’. Foram avaliados crescimento vegetativo,desempenho produtivo das plantas e características físico-químicas dos frutos. A tangerina ‘Sunki’ proporcionou maior volume de copa às plantas de laranja ‘Navelina’, enquanto o citrumelo ‘Swingle’, o citrange ‘Fepagro C-13’ e o limão ‘Cravo’ proporcionaram menor volume. Comparado ao limão ‘Cravo’, o citrumelo ‘Swingle’ proporcionou maior produção acumulada e eficiência produtiva à laranja ‘Navelina’. Todos os porta-enxertos avaliados induziram boa qualidade físico-química aos frutos de laranja ‘Navelina’.

Abstract Studies on rootstocks and scions are of major importance for citrus crop production. The goal of this study was to evaluate vegetative growth, yield performance, and fruit quality of ‘Navelina’ sweet orange trees grafted on five different rootstocks in Northern Parana state, Brazil. The experimental design was completely randomized blocks, with six replications, two plants per plot, and five treatments: ‘Rangpur’ lime; ‘Cleopatra’ mandarin, ‘Sunki’ mandarin; ‘Swingle’ citrumelo; and ‘Fepagro C-13’ citrange. Tree vegetative growth, yield performance, and fruit physical-chemical characteristics were analyzed. ‘Sunki’ mandarin provided the largest canopy volume for ‘Navelina’ sweet orange trees, whereas ‘Swingle’ citrumelo, ‘Fepagro C-13’ citrange, and ‘Rangpur’ lime provided a smaller volume for tree canopy. Compared to Rangpur lime, ‘Swingle’ citrumelo provided higher accumulated yield and production efficiency for ‘Navelina’ sweet orange trees. All rootstocks induced good physical and chemical quality to ‘Navelina’ sweet orange fruits.

RESUMO A laranjeira Pêra, principal cultivar de citros no Brasil, apresenta alta suscetibilidade ao Citrus tristeza virus (CTV), agente causal da tristeza dos citros. No presente estudo foi avaliada a severidade de tristeza dos citros e a sua relação com o desempenho agronômico de sete cultivares e seis seleções de laranjeira Pêra, em experimentos implantados em áreas localizadas nas regiões Norte e Noroeste do estado do Paraná. A avaliação da tristeza dos citros foi realizada com base na severidade dos sintomas de caneluras. O desenvolvimento vegetativo das plantas cítricas foi avaliado nas quatro localidades em 2012, enquanto que a produção foi avaliada em experimentos em duas localidades, para as safras de 2011, 2012 e 2013. A cultivar IPR 153 (Bianchi) apresentou o melhor comportamento em relação à severidade de caneluras nas quatro localidades. A Seleção 27 está entre aqueles com os melhores índices de vigor vegetativo, e também apresentou as maiores produções, acompanhada da cultivar Vimusa e Seleção 12. Além disso, a severidade dos sintomas de caneluras apresentou correlação significativamente negativa com o desenvolvimento vegetativo e a produtividade das plantas. Cabe salientar que as condições ambientais provavelmente tiveram implicações significativas na expressão dos sintomas de tristeza e consequentemente no desempenho agronômico das cultivares e seleções de laranjeira Pêra nas regiões Norte e Noroeste do estado do Paraná.

ABSTRACT ‘Pêra’ 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 ‘Pêra’ sweet orange under field conditions in the North and Northwest regions of the State of Paraná, 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 ‘Pêra’ sweet orange in the North and Northwest regions of the State of Paraná.

Mandarins have become increasingly valued as citrus fruits for the fresh market due to the easy peeling, attractive flavor, and health and nutritional properties. Plant growth and yield, and characteristics of fruits of 'Okitsu' Satsuma mandarin (Citrus unshiu Marc.) trees grafted on nine rootstocks were evaluated in Londrina, northern Paraná, Brazil. The rootstocks were: 'Rangpur' lime (Citrus limonia Osb.); 'Cleopatra' (Citrus reshni hort. ex Tanaka) and 'Sunki' mandarins (Citrus sunki hort. ex Tanaka); 'C-13' [Citrus sinensis × Poncirus trifoliata (L.) Raf.] and 'Carrizo' citranges [C. sinensis × P. trifoliata (L.) Raf.]; 'Volkamer' lemon (Citrus volkameriana V. Ten. & Pasq.); trifoliate orange [P. trifoliata (L.) Raf.; 'Caipira DAC' sweet orange [C. sinensis (L.) Osb.] and 'Swingle' citrumelo [Citrus paradisi Macfad. cv. Duncan × P. trifoliata (L.) Raf.]. The highest plant growth was for the trees on 'Cleopatra' mandarin and 'Caipira DAC' sweet orange. In contrast, the smallest size was for the trees on 'Volkamer' lemon and trifoliate orange. The largest difference between the trunk diameter below and above the grafting point was induced by 'Swingle' citrumelo. Trees of 'Okitsu' Satsuma mandarin on 'Swingle' citrumelo presented the highest yield, while 'C-13', 'Carrizo', 'Sunki', and 'Swingle' induced the largest fruit masses. With regard to fruit characteristics, 'Carrizo' and trifoliate orange induced the best ratio and juice content. Based on theoretical values, 'Rangpur' lime and 'Volkamer' lemon induced the lowest yields

Na implantação dos pomares cítricos, é importante o uso de cultivares adaptadas às condições locais, de forma a assegurar boa produtividade. A laranjeira-'Pera' [Citrus sinensis (L.) Osbeck] é a cultivar mais importante da citricultura brasileira. O objetivo deste trabalho foi avaliar três clones de laranjeira-'Pera' do Banco Ativo de Germoplasma de Citros (BAG-Citros) do Instituto Agronômico do Paraná - IAPAR (acessos I-58 'Pera Vacinada 3', I-59 'Pera Vacinada 4' e I-89 'Pera Bianchi') enxertados sobre o limoeiro-'Cravo' (Citrus limonia Osbeck), nas condições edafoclimáticas de Londrina-PR. As plantas cultivadas no espaçamento 7,0 m x 6,0 m foram conduzidas sem irrigação e avaliadas em relação à produção por planta e às características físico-químicas dos frutos. Os clones de laranjeira I-58 'Pera Vacinada 3', I-59 'Pera Vacinada 4' e I-89 'Pera Bianchi' apresentaram em nove safras, produção média anual por planta de 164,10 kg, 133,96 kg e 131,03 kg, respectivamente. Não houve diferença estatística entre os clones para as variáveis estudadas nas 14 safras. A qualidade dos frutos foi a seguinte: para I-58 'Pera Vacinada 3' e I-59 'Pêra Vacinada 4' e I-89 'Pera Bianchi', respectivamente: 159,6 g, 149,9 g e 150,9 g para massa de fruto; sólidos solúveis de 11,16 ºBrix, 10,98 ºBrix e 10,65 ºBrix; acidez titulável de 1,07%, 1,12% e 0,99%; teor de suco de 50,8%, 52,9% e 49,7%; ratio de 10,6; 10,0 e 10,9 e índice tecnológico de 2,31; 2,34 e 2,15 kg de sólidos solúveis por caixa.

The use of adapted cultivars to the local conditions is important when establishing citrus orchards to ensure good yield. The sweet orange 'Pêra' [Citrus sinensis (L.) Osbeck] is the most important cultivar to the Brazilian citriculture. The aim of this study was to evaluate three clones of 'Pêra' orange trees from the Citrus Active Germplasm Bank of the Instituto Agronômico do Paraná - IAPAR ('Pêra Vacinada 3' accession I-58, 'Pêra Vacinada 4' accession I-59 and 'Pêra Bianchi' accession I-89) in the edafoclimatic conditions of Londrina, Paraná, Brazil. The plants were budded on 'Rangpur' lime (Citrus limonia Osbeck), spaced 7.0 m x 6.0 m and maintained without irrigation. The evaluations were based on plant yield and physical-chemical fruit characteristics. The clones of orange tree I-58 'Pêra Vacinada 3', I-59 'Pêra Vacinada 4' and I-89 'Pêra Bianchi' presented annual yield per plant during nine crop seasons of 164.10 kg, 133.96 kg e 131.03 kg, respectively. There was no significant difference among the clones for the variables studied during 14 crop seasons. The fruit quality was as follows for I-58 'Pêra Vacinada 3', I-59 'Pêra Vacinada 4' and I-89 'Pêra Bianchi', respectively: fruit mass of 159.6 g, 149.9 g and 150.9 g; soluble solids of 11.16 ºBrix, 10.98 ºBrix and 10.65 ºBrix; titratable acidity of 1.07%, 1.12% and 0.99%; juice content of 50.8%, 52.9% and 49.7%; ratio of 10.6; 10.0 and 10.9; and technological index of 2.31; 2.34 and 2.15 kg of soluble solids per box.

Xanthomonas axonopodis pv. citri strains that cause disease in citrus were investigated by pulsed field and plasmid profile analysis. For the first method, genomic DNA was digested by the rare-cutting enzymes Xba I and Vsp I. The strains evaluated were collected in seven different States of Brazil and in Argentina, Bolivia, Paraguay and Uruguay. Genetic variability was found among strains of X. axonopodis pv. citri from different geographical areas Argentina, Bolivia and Uruguay, with similarities varying from 0.62 to 0.83. However, the strains collected in Brazil, despite being from different States, have shown a genetic similarity ranging from 0.83 to 1.00. Cluster analysis showed a relationship between genomic similarity and geographical origin of the strains. Plasmids were observed in all strains, with a total of five different plasmids, with sizes between 57.7 and 83.0 kilobases. The 72.6 kb plasmid was the most frequent, present in 15 out of 22 strains, while the 68.1 kb plasmid was observed in two strains only. Although the plasmid diversity detected in the present study was not very great, the X. axonopodis pv. citri strains evaluated showed a considerable degree of diversity with regard to this extrachromosomal genetic element.