Rose Mary Pio

Resistance and susceptibility of mandarins and their hybrids to Alternaria alternata

Caused by Alternaria alternata, Alternaria brown spot (ABS) is a major fungal disease of mandarins in Brazil, causing serious losses in commercial orchards of Ponkan tangerine (Citrus reticulata Blanco) and Murcott tangor [C. sinensis (L.) Osbeck × C. reticulata Blanco]. The response of 31 accessions/genotypes of mandarins and their hybrids to A. alternata, was evaluated in Sao Paulo state, Brazil. The incidence and severity of the disease in fruit were evaluated in the field, using diagrammatic scale, four times during 2008 and 2009. Based on these data, the area under the disease progress curve (AUDPC) was calculated. In parallel, in vivo and in vitro inoculations with A. alternata were made on leaves to confirm field results. Resistance and susceptibility was evaluated in controlled experiments by counting the number of lesions per leaf using a diagrammatic scale. Most of the genotypes were symptomatic after inoculation with A. alternata with disease most severe on the hybrids Nova, Africa do Sul, Ponkan and Murcott. Cultivars like Cravo, Nules and Ortanique that have excellent fruit quality and had lower AUDPCs, whereas Fremont and Thomas were highly resistant to the fungus and did not show any symptoms in the field or in controlled inoculations. The attractiveness and pronounced flavor of Fremont and Thomas fruit make them new options for the citriculture.

Resposta de diferentes genótipos de tangerinas e seus híbridos à inoculação in vitro e in vivo de Alternaria alternata

ABSTRACT - The confirmation of a new disease in the Brazilian tangerine orchards, the alternaria brown spot, has been concerning citrus growers because of the serious damages to commercial crops of susceptible varieties, such as Ponkan tangerine and Murcott tangor. In this research, in vitro and in vivo inoculations of Alternaria alternata fungus were held in 54 different varieties of the tangerine group selected from the Citrus Germoplasm Bank of the Citros Center APTA Sylvio Moreira, from the Instituto Agronomico, in Cordeiropolis, State of Sao Paulo, Brazil, aiming to find varieties with more resistance. First, a pathogenicity test with ten different A. alternata isolates was made to select the most aggressive one. After this, inoculations in detached leaves and seedlings were held and, approximately two (in vitro) and three (in vivo) days after, the number of lesions in each leaf was counted, and the disease severity estimated with diagrammatic scale help (in vivo). More than a half of varieties showed symptoms of the disease, however with different levels of susceptibility. Varieties like South African tangerine and Orlando tangelo were the most susceptible; on the other hand the satsumas and willow leaf group and some tangerines, showed resistance, indicating new options to the Brazilian citriculture.Index terms: brown spot, Citrus reticulata, varietal resistance.

Morphological characterization of six citrus varieties with ornamental potential

Brazil is the greatest citrus producer in the world, but the cultivation of citrus plants for ornamental purposes is insignificant and the research on this subject is still rare. Citrus plants are impressive for landscaping especially because of their fruits, which have different sizes, shapes and colors, and that, in general, are in natura edible. The objective of this work was to characterize, for landscaping use, six varieties of citrus with ornamental potential: Buddhas Hand citron, Nagami kumquat, Cipo orange, Imperial orange, Faustrine lemon and Venezuela mandarin, cultivated at the germplasm collection of the Centro APTA Citros Sylvio Moreira, of the Instituto Agronomico, located in Cordeiropolis, Sao Paulo State, Brazil. For each variety, 30 leaves, 30 flowers and 30 fruits, all mature, were collected for analysis of their morphological characteristics. The characteristics of the trees were also evaluated. The experimental design was randomized, and each variety was described by the mean value of the 30 measurements of each variable. There were prominent morphological differences amongst the six varieties, and all of them showed landscaping value.

Influência da polinização com variedades de laranja-doce sobre o número de sementes de tangelo Nova

The objective of this work was to study the pollination influence on Nova tangelo seed production. The experiment was carried out in the Polo de Desenvolvimento Tecnologico dos Agronegocios do Sudoeste Paulista/DDD, Capao Bonito, SP, Brazil, during 2004/2005 crop. Nine years old flowers of Nova tangelo plants were treated as follows: 1. Valencia sweet orange pollination; 2. Natal sweet orange pollination; 3. Pera sweet orange pollination; 4. emasculated flower isolation; 5. complete flower isolation and 6. Check (free flower). In May 2005, the fruits were harvested. The highest harvested fruits percentage was obtained in Pera sweet orange treatment (42%). No fruits were obtained in treatments 4 and 5, suggesting that this tangelo did not develop partenocarpic fruits in this study conditions. In cross-pollination treatments was observed between 20 and 23 seeds in the fruits, which shows an evident pollination influence on fruit characteristic. No significant differences were noticed in fruit quality.

Identificação de espécies de citros mediante polimorfismo enzimático

Estudou-se, mediante polimorfismo enzimatico em gel de poliacrilamida, a variabilidade genetica das especies de laranja-doce (Citrus sinensis); laranja-azeda (C. aurantium); tangerinas clementina (C. clementina), sunki (C. sunki), cleopatra (C. reshni) e ponca (C. rsticulata); lima-da-persia (C. limettioides); limao-galego (C. aurantifolia); limao-cravo (C. limonia) e trifoliata (Poncirus trifoliata). Extratos de folhas foram analisados para as isoenzimas de malato deidrogenase (MDH), enzima malica (ME), leucino amino peptidase (LAP), glutamato oxaloacetato transaminase (GOT), fosfoglucoisomerase (PGI), fosfoglucomutase (PGM) e isocitrato deidrogenase (IDH). Verificou-se grande variabilidade genetica interespecifica, porem nenhuma entre os cultivares de laranja-doce. Foram encontradas algumas aloenzimas, alem das referidas pela literatura em gel de amido, como aquelas de uma regiao proxima ao loco conhecido por Pgm-1, responsavel por proteinas monomericas. Este sistema, denominado PGM, revelou a maior diferenciacao entre as especies, tendo apresentado duas regioes distintas com 9 alelos. No sistema MDH, foram considerados dois locas codificando para proteinas dimericas com 7 alelos; no ME, um loco com 3 alelos; no LAP, possivelmente dois locos responsaveis por proteinas monomericas com 4 alelos; no GOT, dois focos com 7 alelos; no PGI, um loco com 3 alelos e no IDH, um loco com 4 alelos.

Comportamento de catorze porta-enxertos para o limão eureka km 47 na região de Araraquara-SP

Fourteen rootstocks were compared in a trial started in 1991, for Eureka lemon cv. km 47, nucellar clone, in Araraquara, Brazil. The rootstocks tested were Orlando and Seminole tangelos (C. reticulata Blanco x C. paradisi Macfad.), Cleopatra mandarin (C. reshni hort. ex Tanaka), Sunki mandarin [C. sunki (Hayata) hort. ex Tanaka], Rangpur Lime (C. limonia Osbeck), Rough Lemon cv. African (C. jambhiri Lush.), and Volkamerican cv Catania 2 (C. volkameriana V. Ten. & Pasq.), sweet orange [C. sinensis (L.) Osbeck] cv. Caipira DAC, sour orange (C. aurantium L.), Poncirus trifoliata (L.) Raf. cv. EEL, P. trifoliata (L.) Raf. cv. Kryder 8-5, Morton citrange [P. trifoliata (L.) Raf. x C. sinensis (L.) Osbeck], C. karna Raf. and C. pennivesiculata (Lush.) Tanaka. Yield was measured by weight of fruits per tree, for a period of five years (1998-2002). The best yielding rootstocks were C. pennivesiculata and Cleopatra mandarin (> 220 kg/tree). Citrus karna, both tangelos, both trifoliates and sweet orange cv. Caipira DAC presented the lowest fruit yields (<180 kg/tree). Fruit quality and percentage of trees affected by gummosis were also studied. No significant variation was observed for fruit quality characteristics for trees on different rootstocks, while trees on C. penivesiculata and sour orange were resistant to gummosis infection.

Florescimento e frutificação em bambu

In February 1977 the flowering and seeding of bamboo specie Melocanna baccifera Kurz was observed at the Campinas Experimental Station. The morphological and botanical characteristics observed showed that the material belongs to the above mentioned specie.