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Doctoral Thesis
DOI
https://doi.org/10.11606/T.11.2020.tde-20200111-132904
Document
Author
Full name
Luciana Veiga Barbosa
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 1998
Supervisor
Title in Portuguese
Citologia de híbridos somáticos de Passiflora spp. obtidos por fusão de protoplastos
Keywords in Portuguese
CITOGENÉTICA VEGETAL
FUSÃO DE PROTOPLASTOS
HIBRIDAÇÃO SOMÁTICA
MARACUJÁ
Abstract in Portuguese
O Brasil é considerado o maior produtor mundial de maracujá, com uma área aproximada de 33.000 ha. No entanto, apresenta baixa produtividade (8 a 10 t/ha) que é motivada principalmente por problemas fitossanitários. Programas de melhoramento genético via hibridação sexual, visando introgredir genes de resistência a doenças presentes em espécies selvagens, têm sido conduzidos, porém, apresentam resultados modestos. Isso se deve ao fato das espécies do gênero Passiflora, além de serem auto-incompatíveis, apresentarem incompatibilidade cruzada, o que limita o uso da hibridação sexual. Uma alternativa para contornar essa barreira é a hibridação somática, via fusão de protoplastos. Dando continuidade à uma linha de pesquisa desenvolvida no Departamento de Genética (ESALQ/USP), esta tese se propôs a apresentar estudos sobre o desenvolvimento vegetativo e reprodutivo de alguns híbridos somáticos obtidos entre a espécie cultivada P. edulis Sims. f. flavicarpa Deg. (E) e, espécies portadoras de genes de resistência a doenças, P. alata (Al), P. amethystina (Am), P. cincinnata (C) e, P. giberti (G), todas com 2n = 2x = 18 cromossomos. As análises citológicas confirmaram a natureza híbrida para (E + Am) e (E + C), pois as plantas dessas combinações apresentaram 2n = 4x = 36 cromossomos. Alterações meióticas como a presença de cromossomos e cromátides atrasadas, cromossomos com ascensão precoce e pontes anafásicas foram observadas. Os híbridos (E + Am) apresentaram configurações do tipo univalentes, bivalentes e tetravalentes, indicando a ocorrência de crossing-over entre cromossomos homeólogos. Todas as plantas híbridas apresentaram elevados valores de viabilidade do grão de pólen, acima de 70%. Os híbridos (E+ C) mostraram, igualmente, irregularidades meióticas e configurações do tipo univalentes e tetravalentes, indicando também a ocorrência de pareamento homeólogo. Entretanto, cerca de 70% das células apresentaram 18 bivalentes, o que explica os altos valores de viabilidade do grão de pólen observados. Os híbridos (E + AI) e (E + G) mostraram 2n = 2x = 18 cromossomos, foram fenotipicamente semelhantes aos parentais selvagens, com meiose regular e elevada viabilidade do grão de pólen. Nesse caso, provavelmente, ocorreu
Title in English
Not avaliable
Abstract in English
Brazil is considered the world's greatest passionfruit producer, with approximately 33,000 ha of area. Howerver, the yield is low (8 to 10 t/ha), which is mainly due to phytosanitary problems. Breeding programs, via sexual hybridization, aiming at introgressing resistance genes from wild species, have been conducted, but with modest results. This is caused by self-incompatibility and cross-incompatibility of the species from Passiflora genus, which impairs the utilization of sexual hybridization. An alternative to supars this barrier is somatic hybridization, via protoplast fusion. Following a research line developed at Genetic Department (ESALQ/USP - Piracicaba/SP), this thesis work proposes to present studies on vegetative and reproductive development of somatic hybrids between the commercial species P. edulis Sims f. flavicarpa Deg. (E) and wild species carrying disease resistance genes, P. alata (AL), P. cincinnata (C), P. giberti (G) and P. amethystina (Am), all with 2n = 2x = 18 chromosomes. Cytological analyses confirmed the hybrid nature of (E + Am) and (E + C), as hybrids plants from these combinations showed 2n = 4x = 36 chromosomes. Meiotic alterations with presence of laggard chromosomes and chromatids, early segregating chromosome and anaphase bridges were observed. Toe hybrids (E + Am) showed univalent, bivalent and quadrivalent kinds of configurations, showing the occurrence of crossing-over between homoeologous chromosome. All hybrids had high polen viability values, up to 70 %. Somatic hybrids (E + C) showed equally meiotic irregularities and univalents or quadrivalents configuration, also indicating occurence of homoelogous pairing. However, around 70 % of the cells showed 18 bivalents, which explains the high polen viability values. Somatic hybrids (E + AI) and (E + G) showed 2n = 2x = 18 chromosomes, there were phenotipically similar to wild type parents and presented regular meiosis with nine bivalents formation and high polen viability. In this case, commercial parent chromosome elimination has likely occurred. Poliploid effect on lower epidermis cells of (E + Am) and (E + C) hybrids plants was studied. As the ploidy level increased in the plants, a greater surface area and smaller stomata number were observed
 
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Publishing Date
2020-01-11
 
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