Pachytene Karyology of Ipomoea biloba

抄録

The entire haploid complement of the pantropical diploid (2n=30) Ipomoea species, I. biloba Forsk has been identified at pachytene stage employing criteria such as relative length, centromere position, nucleolar association, distribution and length of dark- and light-staining segments in the arms and chromomere number, size and pattern of distribution. The diagnostic features of the differentiated pachytene bivalents and the idiogram at this stage are presented. The advantages of pursuing karyological studies at pachytene over that at somatic metaphase in this species is brought out. From a comparative study of pachytene karyotypes of I. biloba and the earlier investigated I. crassicaulis with which it has been recently hybridized, homoeology of eight chromosomes could be adduced. The need for pachytene analyses in this inter-specific hybrid, other releated species and their hybrids is emphasized. Later stages of meiosis were found to be normal leading to formation of over 95% stainable pollen.