Meiotic irregularities associated to cytomixis in Buddleja iresinoides (Griseb.) Hosseus. (Buddlejaceae) and Castilleja arvensis Schltdl. & Cham. (Orobanchaceae)

The current paper analyzes the male meiotic behavior in wild populations of Buddleja iresinoides and Castilleja arvensis from Piedmont areas of the Northwest Region of Argentina. Castilleja arvensis showed tetraploid number of chromosome of 2n = 24. Our results are not in agreement with the previously reported base number x = 19 for Buddleja and the chromosome number n = 28 found for B. iresinoides is atypical in the genus. Around 7 % pollen mother cells were aneuploid as they showed meiotic chromosome count of n = 20-21 bivalents. Possible origin for such atypical chromosome number has been discussed in this paper. During the cytological studies we also came across pollen mother cells showing meiotic abnormalities such as cytomixis, chromatin stickiness and anaphase bridges with lagging chromatin. Consequently microsporogenesis was also irregular showing dyads and triads. However, the percentage of these irregularities during meiosis and microsporogenesis was not higher, and pollen fertility was not affected to a great extent. Cytomixis and other meiotic abnormalities in these species are reported here for the first time.