Citrus huanglongbing (HLB), associated with Candidatus Liberibacter asiaticus and Ca. L. americanus and transmitted by the Asian psyllid Diaphorina citri, is the most serious disease of citrus worldwide because of crop devastation and difficulty to control. Since 2004, approximately 3 million trees were eliminated in attempts to limit its spread in Brazil. Where HLB becomes endemic, the disease progression in the orchard and the increasing symptom severity throughout the tree canopy can be relatively fast, greatly reducing the economic life of affected orchards because of tree decline and yield reduction. Although the majority of the fruit from symptomatic branches drop before harvest, a significant amount of affected fruit remain attached, are available for harvest, and can affect juice quality. To quantify and compare the effects of HLB on fruit quality of the most important sweet orange cultivars grown in São Paulo State, 4-6 year-old sweet orange trees from 26 blocks (two of 'Valencia Americana', eight of 'Hamlin', four of 'Westin', seven of 'Pera', and five of 'Valencia') were selected prior to harvest. In each block, 14-21 HLB-symptomatic trees were chosen. In each tree, the quality of 20 fruit normal in appearance from asymptomatic branches and 20 symptomatic fruit from symptomatic branches were assessed. In general, compared to normal fruit, the symptomatic fruit were small, light, more acidic, and had lower juice percentage, Brix, total soluble solids per box, total soluble solids per fruit, and Brix/acidity ratio. These effects of fruit quality were less pronounced on early and mid season sweet orange cultivars than on late season cv. Valencia.

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Introduction. Tahiti lime trees grafted on Rangpur lime grown in São Paulo State, Brazil, in subtropical climatic conditions, have a high level of vigor, poor tolerance to Phytophthora spp. and low productivity. Using Poncirus trifoliata var. monstrosa Flying Dragon rootstock which allows one to obtain dwarfed trees and high yields could solve this problem. Materials and methods. In an experiment set up in November 1994 in Brazil, the tree size, fruit production and quality of Tahiti lime grafted on trifoliate orange Flying Dragon were evaluated at four planting spaces: 4 m × 1 m (2 500 trees•ha-1); 4 m × 1.5 m (1 666 trees•ha-1); 4 m × 2 m (1 250 trees•ha-1) and 4 m × 2.5 m (1 000 trees•ha-1), in a randomized block design, with four trees per plot. The cultural practices did not include supplementary irrigation. Results. Trees planted in the 4 m × 1 m planting space had greater canopy diameters (2.75 m) than trees planted with the other planting spaces. Whatever the densities considered, tree height did not differ. Average fruit yield (1998 to 2000) was the greatest on the 4 m × 1 m planting space with 21.6 t•ha-1 , significantly differing from the 4 m × 2.5 m planting space with 13.1 t•ha-1. Fruit quality was affected by the plant planting space, but all the production was commercially acceptable. Discussion. The use of a high density planting of Tahiti lime grafted on P. trifoliata var. Flying Dragon would be of commercial interest, due to greater yields than trees in traditional cropping systems. Brazil / Citrus latifolia / rootstocks / dwarfs / density / yields Performance de la lime Tahiti greffée sur Poncirus trifoliata var. monstrosa Flying Dragon en fonction de quatre densités.

Foi instalado um experimento de seleção de porta-enxertos para a lima-ácida-'Tahiti' (Citrus latifolia Tanaka), em dezembro de 1988, na Estação Experimental de Citricultura de Bebedouro-SP, com o objetivo de conhecer seu comportamento e oferecer novas opções de plantio para as condições ecológicas semelhantes às daquela região. A variedade copa, originária do BAG-Citros do IAC, localizado no Centro de Citricultura Sylvio Moreira, Cordeirópolis-SP, é um clone nucelar de 'Tahiti', denominado IAC-5. Os porta-enxertos, que tiveram a mesma origem, foram: tangerinas-'Sunki' (Citrus sunki Hort. ex Tanaka); 'Cleópatra'(Citrus reshni Hort. ex Tan.); 'Batangas' e 'Oneco' (Citrus reticulata Blanco); trifoliata-EEL (Poncirus trifoliata Raf.); limão-'Cravo' (Citrus limonia Osbeck); limão-'Volkameriano Catania 2' (Citrus volkameriana Tan. & Pasq.); tangelo-'Orlando' (C. reticulata Blanco x Citrus paradisi Macf.); citrumelo-'Swingle' (P. trifoliata Raf. X C.paradisi Macf.); citrange-'Morton' (P. trifoliata Raf. X C. sinensis (L.) Osbeck) e laranja-'Caipira DAC' (C. sinensis (L.) Osbeck). Com relação à produção, avaliada no período de 1991 a 1998, os porta-enxertos de melhor comportamento foram o tangelo-'Orlando', citrange-'Morton' e citrumelo-'Swingle'. As mais baixas produções ocorreram nos porta-enxertos de tangerina e de laranja-'Caipira DAC'. O limão-'Cravo' apresentou produção intermediária e proporcionou curta vida útil às plantas.

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RESUMOA clorose variegada dos citros (CVC) é uma doença que tem promovido sérios prejuízos aos laranjais das regiões Norte e Nordeste do Estado de São Paulo, onde a deficiência hídrica e as altas temperaturas são mais frequentes. Assim, este trabalho objetivou a avaliação do efeito da deficiência hídrica no desenvolvimento de sintomas fisiológicos em laranjeira 'Natal' com CVC. Foram realizadas medidas do potencial da água na folha, transpiração, condutância estomática e assimilação de CO 2 , em laranjeiras em condições naturais e submetidas à irrigação. O delineamento experimental foi em blocos ao acaso com cinco repetições. A condutância estomática, a transpiração diária e o potencial da água na folha foram menores nas plantas com CVC. A assimilação diária de CO 2 foi menor nas laranjeiras com CVC mesmo quando irrigadas. De fato, a irrigação diminuiu o efeito da CVC, porém não impediu o estabelecimento da doença em laranjeiras inoculadas com Xylella fastidiosa. Em relação aos demais tratamentos, as plantas infectadas e mantidas sob condições naturais (sem irrigação) apresentaram maior comprometimento das trocas gasosas, mesmo quando as avaliações fisiológicas foram feitas em período úmido (verão).Palavras-chaves: Citrus sinensis, relações hídricas, trocas gasosas, Xylella fastidiosa. ABSTRACT WATER DEFICIENCY INTENSIFIES PHYSIOLOGICAL SYMPTOMS OF CITRUS VARIEGATED CLOROSIS IN 'NATAL' SWEET ORANGE PLANTSCitrus variegated chlorosis (CVC) is a disease that has caused serious economical losses in citrus grove located in the North and Northeastern regions of São Paulo State, where water deficiency and high temperature occur frequently. Therefore, the aim of this work was to evaluate the influence of water deficiency on the development of physiological symptoms in 'Natal' sweet orange plants with CVC. Measurements of leaf water potential, transpiration, stomatal conductance e CO 2 assimilation were taken in plants under natural conditions and submitted to irrigation. The experimental design was in randomized blocks, with five replications. Stomatal conductance, daily transpiration and leaf water potential were lower in CVC-affected plants. The daily CO 2 assimilation was reduced in CVC-affected plants, even in irrigated ones. In fact, irrigation decreased the negative effects of CVC, however, it did not prevent disease establishment in sweet orange plants inoculated with Xylella fastidiosa. Compared to other treatments, infected plants submitted to natural conditions (without irrigation) exhibited higher constrain of leaf gas exchange, even when measurements were taken during humid period (summer).

1,61 e 3,03 t/ha de matéria seca, respectivamente, considerando plantio apenas na área intercalar de citros (50% da área total). A análise química do material seco revelou a incorporação de volume considerável de N, P 2 O 5 , K 2 O, Ca, Mg, S, B, Cu, Fe, Mn e Zn pelas leguminosas, onde podemos considerar que parte do N é proveniente da fixação simbiótica do N 2 atmosférico pelas leguminosas e o restante e demais nutrientes provenientes do importante processo de reciclagem de nutrientes do solo, que são absorvidos pelas leguminosas das camadas subsuperficiais e incorporados na superfície do solo, onde estarão novamente disponíveis às plantas cítricas. A C. juncea foi a espécie que se destacou como maior produtora de biomassa e incorporadora de nutrientes, seguida pelo C. cajan e C. ensiformis. : 6,55; 1,23; 3,42; 1,78; 1,75; 1,61 and 3,03 t/ha of dry matter, respectively, considering the cultivation only at the middle of the citros orchard (50% of the total area). The chemical analysis of the material, revealed a considerable incorporation of N, P 2 O 5 , K 2 O, Ca, Mg, S, B, Fe, Mn and Zn by leguminous plants, where we consider a parcel of the N comes from the atmospheric symbiotic fixation in the leguminous plants and the remaining and other nutrients comes from the recycling process of nutrients of soil, that are absorbed by the leguminous plants of the sub-superficial and incorporated in surface of the soil, where they will be again available to citrus plants. C. juncea produced the highest amount of biomass and incorporation of nutrients, followed by the C. cajan and C. ensiformis. Termos para indexação: Citrus sinensis, leguminosas, Crotalaria juncea, Crotalaria spectabilis, Cajanus cajan, Mucuna aterrima, Mucuna deeringiana, Dolichos labe-labe, Canavalia ensiformis RECICLYING AND INCORPORATION OF NUTRIENTS TO THE SOIL IN ORCHARD OF 'PERA' ORANGE BY CULTIVATION WITH COVER CROPS ABSTRACT -