Division of Botany, Indian Agricultural Research Institute, New Delhi-12
1. The karyotype of a tall variety of coconut was studied using relative length, and arm ratio and the position and number of secondary constrictions as criteria for classification. A majority of chromosomes had sub-median centromere and there were considerable differences in length. Two pairs were satellited.
2. Microsporogenesis was studied in trees of Laccadive Ordinary, Apricot and Dwarf Red, which are tall, semi-tall and dwarf varieties of coconut respectively. Meiosis was regular in Laccadive Ordinary while irregularities such as heterozygosity for translocations and inversions, reduced chiasma frequency, persistent nucleoli, chromosome mosaic cells, lagging chromosomes at AI and AII, micronuclei at telophase and sporads with varying number of spores were observed in Apricot and Dwarf Red. The frequency of aberrant cells was higher in Apricot.
3. Laccadive Ordinary, Apricot and Dwarf Red had on an average 5, 30 and 30 per cent of sterile pollen respectively in studies carried out over a period of two years.
4. The cytological behaviour of the semi-tall and dwarf varieties resembles that of inbred rye. It is suggested that the dwarf coconut may owe its origin to inbreeding facilitated by the imposition of a self-pollinating device. The dwarf palms may, therefore, offer excellent material for evolving high yielding hybrid trees. The only instance of a cross between two distinct dwarfs reported in the literature supports this view.
