Morfologia floral, citometria de fluxo e citogenética em Lycopersicon esculentum Mill. acesso BGH 160 / Floral morphology, flow cytometry and cytogenetic in Lycopersicon esculentum Mill. access BGH 160

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Tomato (Lycopersicon esculentum Mill.) is the second most cultivated vegetable in the world. In Latin America the largest producer is Brazil, with a total area of 58,5 thousand hectares and production of 3,3 thousand tons. Part of the increase in production has been attributed to investments in breeding programs and to innovations generated by biotechnical processes. In this context cytogenetical and cytometrycal studies can contribute to breeding programs. Considering the existent controversies in the literature and the need of expanding the knowledge about the characteristics of this genome, the present work had three main objectives in L. esculentum access BGH 160: (i) characterization of the morphological differences in floral buttons, (ii) quantification of the DNA content and ploidy evaluation in leaves and floral pieces at different stages of development and (iii) cytogenetic reevaluation of the karyotype. During the evaluation and morphological characterization accomplished in L. esculentum access BGH 160, plants were observed with normal and abnormal behavior concerning the structure of the floral buttons. The abnormal plants presented modifications in morphology and floral constitution, fruit formation and structure, and absence of seeds. However, the phenotypic behavior alone was not sufficient to identify the possible cause of alteration in the abnormal plants in this access. A hypothesis was postulated in that structural or numerical alterations in the chromosome could explain the abnormality. Differences were verified through quantification of the nuclear DNA content, with normal plants presenting 2C = 1,96 pg and abnormal plants presenting 2C = 1,87 pg of DNA. By the ploidy analysis in seven terminal leaf of the normal plants, at different developmental stages, ploidy variation of 2C, 4C to 8C was verified, increasing according to the stage of physiological development. When ploidy variation was related with the leaf area, correlation was observed between the two variables in the normal plants with nuclei 4C. However, in the abnormal plants, the leaf area did not correspond to the ploidy variation, so much so that the correlation between the ploidy level and the leaf area was negative for the nuclei 8C. Considering that the different behavior of the abnormal plants could be related with the difference on DNA content, this study concentrated on the cytogenetic evaluations between these two types of plants. The complement of the normal plant presented 2n = 24 chromosomes, with one pair (6) of chromosomes being metacentric, and all others submetacentric. The Ag-NOR banding in L. esculentum var. Stupnické evidenced the active NOR in the medium portion of chromosome 1, and identified a deletion in one of the homologues of pair 1, in the abnormal L. esculentum access BGH 160. It was concluded that a deletion is probably responsible for the morphologic alterations of the floral buttons and fruits.

ASSUNTO(S)

tomate dna quantification deleção ploidia genetica vegetal quantificação de dna lycopersicon esculentum lycopersicon esculentum ploidy cariótipo citogenética tomato karyotype cytogenetics morfologia floral floral morphology citometria de fluxo flow cytometry

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