04574nam a2200757 a 450000100080000000500110000800800410001902200140006010000280007424500810010226000580018330000100024149000560025152023850030765000130269265000230270565000110272865000260273965000220276565000180278765000170280565000220282265000190284465000140286365000190287765000170289665000140291365000230292765000170295065000180296765000090298565000110299465300300300565300110303565300240304665300230307065300240309365300300311765300180314765300270316565300270319265300310321965300270325065300210327765300220329865300260332065300260334665300350337265300340340765300240344165300290346565300240349465300340351870000220355270000200357470000260359470000230362070000200364370000220366370000160368570000170370170000260371870000280374470000180377270000260379016527372016-05-18       2003    bl uuuu     u0uu1 u    #d  a1516-57281 aSOARES FILHO, W. dos S.  aCitrus breeding program at Embrapa Cassava & Fruitsbdevelopment of hybrids.  aCruz das Almas: Embrapa Mandioca e Fruticulturac2003  a39 p.  a(Embrapa Mandioca e Fruticultura. Documentos, 107).  aIn order to obtain new citrus varieties, better adapted to tropical conditions, the Embrapa - National Cassava & Fruits Research Center (CNPMF), as known as Embrapa Cassava & Fruits, has started in September 1988 a hybridization program based on its own Active Germplasm Bank, which shows a great genetic variability, represented for about 700 accesses, comprising several Citrus species and varieties, besides close relative genera, among which are inclused Poncirus, Fortunella, Microcitrus, Eremocitrus and Severinia, among others of smaller importance, under the point of view of genetic improvement. The program was set up due to the relatively low longevity of the citurs orchards, whose life span is around 15 to 18 years in the main producing areas of São Paulo State, that represents about 75% of the Brazilian production, and from 12 to 15 years in the North and Northeast regions of the country. As immediate objectives, the program aims at selection of genotypes, particularly rootstocks, tolerant to drought conditions and aluminum toxicity, resistant to diseases such as Phytophthora root rot and Citrus Tristeza Virus - CTV, and adapted to high density tree population. A multidisciplinary research group is involved in these studies and several research activities are underway,  mainly: a) hybridization, including varieties of high agronomic valoe and/or adaptive potential to grow in abiotic and biotic stresses; b) identification of hybrid embryos and early identification of zygotic seedlings by analysis of foliar morphology, isoenzymes, polymorphic DNA segments and chromosome banding; c) studies concerned to in vitro cultivation of citrus embryos, as well as to the complement of the embryogenesis of zygotic embryos starting from early stages, avoiding or restricting the presence of nucellar embryos, particularly in polyembryonic varieties, used as female parents in artificial hybridizations; d) identification of promising parents regarding to obtaining new hybrid varieties, rootstocks and scions; e) definition of methodologies for early selection of hybrids tolerant to drought and aluminum toxicity, as well as resistant to Phytophthora root rot and CTV; f) establishment of methodologies for early flowering induction, aiming at shortening the pre-reproductive period of selected hybrids; g) development of somatic hybrids by protoplast fusion.  abreeding  achromosome banding  aCitrus  aCitrus tristeza virus  adrought tolerance  ahybridization  apolyembryony  aprotoplast fusion  atissue culture  aAlumínio  aFruta cítrica  aHibridação  aIndução  aMarcador Molecular  aMelhoramento  aPoliembrionia  aSeca  aVírus  aBandeamento cromossômico  aCitros  aCitrus trieza virus  aCultura de tecidos  aCultura dos tecidos  aEarly flowering induction  aFlorescimento  aFusão de protoplastos  aGomose de Phytophthora  aIndução de florescimento  aMarcadores moleculares  aMolecular makers  aMolecular markers  aPhutophthora root rot  aPhytophthora root rot  aTolerance to aluminum toxicity  aTolerance to alumium toxicity  aTolerância à seca  aTolerância ao alumínio  aTristeza dos citrus  aVírus da tristeza dos citros1 aVILARINHOS, A. D.1 aALVES, A. A. C.1 aCUNHA SOBRINHO, A. P.1 aOLIVEIRA, A. A. R.1 aSOUZA, A. da S.1 aLEDO, C. A. da S.1 aCRUZ, J. L.1 aSOUZA, L. D.1 aCASTRO NETO, M. T. de1 aGUERRA FILHO, M. dos S.1 aPASSOS, O. S.1 aMEISSNER FILHO, P. E.