Juiz de Fora-MG, Brazil
Universidade Federal de Juiz de Fora
Viÿosa-MG, Brazil
Universidade Federal de Viÿosa
Influence on seed size of chromosomal abnormalities in maize cells resulting from irradiated pollen --Viccini, LF, de Carvalho, CR The production of plants with chromosomal variations has evolved as a valuable cytogenetic tool for gene identification, isolation and mapping using molecular approaches. Considering the difficulty of identifying these plants, the determination of indicators of the existent level of alteration is important to facilitate the selection of abnormal plants. With the objective of verifying the relationship between seed size and chromosomal abnormalities in maize meristematic and meiotic cells resulting from irradiated pollen, maize tester line L-869 of the Federal University of Viÿosa pollen was exposed to 36 and 72 Gy of gamma irradiation and soon thereafter used for pollination. The seeds originating from those two doses were ranked in size classes in order to relate with the percentage of chromosomal alterations. For mitosis study, seeds were germinated in Petri dishes with a film of distilled water in the dark at 28-29 C. Root tips ranging from 0.5 to 1.0 cm in length were fixed in fresh cold methanol-acetic acid (3:1). Slides were prepared by the air drying technique with enzymatic maceration. After drying on a hot plate, the slides were stained with Giemsa solution. The percentage of abnormal anaphase cell carriers chromosomal bridges was evaluated. In the meiosis study, seeds were germinated in a greenhouse so that the immature tassels were collected at the appropriate stage. Slides were also prepared by the air drying technique. Deficiencies, heteromorphic pairs, partial pairing, laggards, bridges, fragments, fusions, translocations and cells with altered chromosome number due to structural anomalies were observed. The statistical analysis was carried out splitting the sum of the squares for treatments in orthogonal contrasts. Considering the 35.7 Gy dosage-irradiated meristematic cells, no relation was detected between size of the seeds and percentage of abnormal anaphases, while for the 71.4 Gy dosage it was possible to verify an increase of the percentage of abnormal anaphases with the decrease of seed size. Regarding the meiotic cells, the relationship between seed size and levels of chromosomal variations was verified for both radiation doses (36 e 72 Gy). That is to say, small seeds presented a larger number of chromosomal variations. The analysis of M1 plants confirmed this relationship, with smaller-sized plants being observed when small seeds were germinated.
 
 
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