Erratic Male Meiosis Resulting in2nPollen Grain Formation in a 4x Cytotype (2n=28) ofRanunculus laetusWall. ex Royle

Abstract

Two accessions were studied for male meiosis inRanunculus laetusfrom the cold regions of Northwest Himalayas. One accession showed the presence of 14 bivalents at diakinesis and regular segregation of bivalents at anaphase I which lead to normal tetrad formation with fournmicrospores and consequentlynpollen grains and 100% pollen fertility. Second accession from the same locality revealed the erratic meiosis characterized by the presence of all the 28 chromosomes as univalents in meiocytes at metaphase I. Univalent chromosomes failed to segregate during anaphases and produced restitution nuclei at meiosis I and II. These restitution nuclei resulted into dyads and triads which subsequently produced two types of apparently fertile pollen grains. On the basis of size, the two types of pollen grains were categorized asn(normal reduced) and2n(unreduced, 1.5-times larger than thenpollen grains). The estimated frequency of2npollen grains from dyads and triads (61.59%) was almost the same as that of the observed one (59.90%), which indicated that2npollen grains inR. laetuswere the result of dyads and triads. The present paper herein may provide an insight into the mechanisms of the formation of various intraspecific polyploids through sexual polyploidization inR. laetus.