Meiotic behavior of several Brazilian soybean varieties

Abstract

Despite the importance of soybeans little cytogenetic work has traditionally been done, due to the small size and apparent similarity of the chromosomes. Fifteen soybean [Glycine max (L.) Merrill] varieties adapted for cultivation in two distinct regions of Brazil were analyzed cytogenetically. A low frequency of meiotic abnormalities was noted in all varieties, although they were not equally affected. Irregular chromosome segregation, chromosome stickiness, cytoplasmic connections between cells, cytomixis and irregular spindles were the main abnormalities observed, none of which had been described previously in soybeans. All of these abnormalities can affect pollen fertility. Pollen fertility was high in most varieties and was correlated with meiotic abnormalities. Although soybean is not a model system for cytological studies, we found that it is possible to conduct cytogenetic studies on this species, though some modifications in the standard methods for meiotic studies were necessary to obtain satisfactory results.

Meiotic Behavior of Wild, Synthetic and Cultivated Wheats

“…The diploid wild and tetraploid cultivated species recorded a meiotic index of 100%. These results are in agreement with those of Bione et al (2000) who demonstrated that the percentage of cells with meiotic abnormalities was higher at metaphase but decreased until telophase II, indicating that some chromosomes were included in the main nucleus. This seems to be normal behavior in many species (Koduru and Rao 1981).…”

“…squarrosa (458) possessed the highest amount of laggard chromosomes at the anaphase and telophase stages (Table 2). Chiasma are responsible for the maintenance of bivalents which permit normal chromosome segregation (Bione et al 2000); therefore, any failure in chiasma formation and/or the occurrence of any crossing-over may lead to laggard chromosomes.…”

“…Precocious migration of chromosome to the poles is a very common abnormality among plants (Pagliarini andPereira 1992, Consolaro et al 1996). Precocious chromosome migration to the poles may have resulted from univalent chromosomes at the end of prophase I or precocious chiasma terminalization in diakinesis or metaphase I. Univalents may originate in the absence of crossing-over in pachytene or from synaptic mutants (Bione et al 2000). During the disjunction of chromosomes at anaphase-I to telophase-I or anaphase-II to telophase-II, the univalent may either be included in a daughter nucleus or lag, divide, or misdivide (Singh 2003).…”

“…The failure of chromosome pairing or formation of multivalent chromosomes has often been observed even in pure varieties of common wheat (Watanabe 1962). Studies indicated that the percentage of cells with meiotic abnormalities was higher in metaphase I but decreased until telophase II, indicating that some chromosomes were included in the main nucleus (Bione et al 2000). Therefore, determination of the meiotic index revealing the percentage of normal tetrads and stability of meiotic behavior has been considered as an important criterion in meiotic studies of plant species.…”

Meiotic behavior of economically important plant species: the relationship between fertility and male sterility

“…In all species in which irregular chromosome segregation occurred a correlation between this characteristic and pollen fertility or seed production was observed. Another more rare segregational abnormality observed was non-congressed bivalents at the equatorial plate in metaphase I, only found in Chlorophytum comosum , Glycine max (Bione et al, 1999) and Avena sativa (Baptista-Giacomelli, 1999).…”