Resumen de Impaired Male Meiosis due to Irregular Synapsis Coupled with Cytomixis in a New Diploid Cytotype of Dianthus angulatus (Caryophyllaceae) from Indian Cold Deserts

Puneet Kumar, Vijay Kumar Singhal, Dalvir Kaur

• Dianthus angulatus (Caryophyllaceae) is cytologically examined here for the first time for the area of India. The diploid chromosome count of 2n?=?30, ascertained here, represents a new cytotype, supplementing the earlier report of a hexaploid cytotype with 2n?=?90 from outside of India. We report here the occurrence of two plants showing impaired meiosis due to irregular synapsis and cytomixis collected from Kinnaur district, Himachal Pradesh (India). The other plants of this species collected in Lahaul-Spiti region showed normal male meiosis (n?=?15) with a high (95%-100%) pollen fertility and normal seed set, and they reproduce sexually. Irregular synapsis in two plants from the Kinnaur region is characterized by the complete absence of chromosome pairing and the presence of 30 univalents at diakinesis and meta-anaphase. In addition, other meiotic irregularities were found, such as unoriented chromosomes, laggards, precocious movements of univalents at anaphase-I and micronuclei at telophase. Microsporogenesis was also abnormal, resulting in the formation of monads, dyads, triads, polyads, and tetrads with micronuclei. The occurrence of intra- and intermicrosporal chromatin material transfer during microsporogenesis was observed, which is a rather rarely observed phenomenon. The synaptic irregularities coupled with chromatin transfer in these plants seem to be responsible for the high pollen sterility (38%-42%) and heterogeneously sized pollen grains. In these plants no seeds were set, and plants reproduced vegetatively through root suckers.