Meiotic Configuration of a Cultivated Rye Collected from China

Go Horiuchi, Katsumasa Niwa, Yasokazu Hirai
In addition to the normal chromosome complement (A chromosomes), supernumerary chromosomes (B chromosomes) have been found in over a thousand higher plant species (Jones and Rees 1982) . 'So far, many populations of cultivated rye (Secale cereale L.) were found to contain the standard type of B chromosomes (Muntzing 1954 , 1957 , Niwa et al. 1990 ) which were about half as large as A chromosomes and had a subtelocentromere (Muntzing and Lime-de-Faria 1952). Recently, Niwa and Sakamoto (1994)
more » ... nd a cultivated rye with the standard B chromosomes which was originally collected from China. Using this natural population of cultivated rye from China, the pairing between B chromosomes and the effect of B chromosomes on chiasma frequency of A chromosomes at the first meiotic metaphase (MI) of pollen mother cells (PMCs) were investigated. Moreover, the spontaneous reciprocal translocation heterozygotes of A chromosomes were also analyzed and described. Materials and methods The spike samples of S. cereale were originally collected by Prof. S. Sakamoto from a pure rye field along the way from Liziping to Tuoniao in Sichuan Province in China in 1988. Twenty spikes were used with three grains randomly selected from each spike and a total of 60 grains examined. Of the 60 plants grown, two plants had one standard B chromosome (1B), 20 plants had two standard B chromosomes (2B), three plants had four standard B chromosomes (4B) while the rest had no B chromosomes (Niwa and Sakamoto 1994). Young anthers from the plants with B chromosomes (25 plants) and without B chromosomes (15 plants) were initially examined by the acetocarmine smear method to check that the cell stages corresponded to MI and were later fixed in Farmer's solution consisting of absolute ethanol and glacial acetic acid (3:1). The fixed anthers were stained in 1% acetocarmine for 5-7 days and subsequently, chromosome preparations were made by the acetocarmine squash method. Fifty PMCs were scored for the pairing and chiasma frequency in each plant. Chiasma frequency was expressed as the mean number of chiasmata per PMC per plant. Results To clarify the pairing between B chromosomes, chromosome pairing of B chromosomes at MI of PMCs was examined (Table 1 and Fig. 1) . None of the B chromosomes paired with the A chromosomes. In 2B plants, 89.9% of PMCs observed formed a bivalent of B chromosomes. In 4B plants, two bivalents of B chromosomes were most frequently observed, and a multivalent (either In, or 1IV) of B chromosomes was observed in 39.3% of PMCs. Table 2 shows configuration of multivalent of B chromosomes at MI of PMCs in 4B plants. Only a Y-shaped trivalent was observed. Three kinds of quadrivalents were further observed which were formed
doi:10.1508/cytologia.60.243 fatcat:7tpcztppv5dh7pibnfqi33akru