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.
Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.
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