Cytomorphological studies on the colchiploids of capsicum frutescens L.

Abstract

The present investigation deals with a morphological and cytological comparison between the colchiploids of Capsicum frutescens cultiver Oshkhosh and its diploid progenitor. The most effective treatment for the induction of tetraploids was found to be 0.2% aqueous colchicine applied to the growing point of young seedlings for 12 hours. On the whole 64% of the plants became polyploids and survived. The induced tetraploid was characterised by deep green, thick and rough leaves with larger epidermal cells, stomata, palisade and spongy parenchyma. The number of stomata per unit area in the tetraploid was less than that of the diploid. In general the morphological characters were larger in the polyploids than their counterparts in the diploids. The 4n plants were completely sterile and no fruit setting was observed in them. The cause of complete failure of fruit formation lies in the premature disintegration of the stigma which blocks the passage of the pollen tube to reach the egg. Pollen germination in situ has been observed in anthers of a polyploid bud. The induced polyploids exhibit cytological abnormalities such as univalents, laggards, restitution nuclei, non-congression and non-orientation of certain bivalents and other irregularities such as subdivision of the chromosome complement into 2 or more groups that function independently within the cell, nondisjunction of chromosomes and unequal distribution of the chromosomes to the polar regions at anaphase were noted at either or both meiotic divisions in the PMC's. The number of microspores per PMC varied from 1-12. The gametes produced by a polyploid with such a cytological mechanism will have extremely variable chromosome number. Those gametes which have balanced genomes will be functional. The evolutionary significance of the various anomalies observed and their importance to plant breeder have been discussed. © 1964, Japan Mendel Society, International Society of Cytology. All rights reserved.