Some Cytolocical Aspects of Autotetraploid Sorghum Improvement

Abstract

Regular chromosome behaviour is important in natural and artificial polyloids whenever the saleable product of crops depends on the efficiency of sexual reproduction. For example, bread wheat (Triticum aestivum) which is a natural allohexaploid, has a genetic system which favours bivalent formation by restricting pairing to fully homologous chromosomes. In addition to the more commonly used agronomic characters, a cytological basis for selection would be a valuable technique for the improvement of artificially induced polyploids of cereals in which irregular chromosome behaviour frequently occurs. Studies of chromosome pairing therefore form an important part of improvement programmes for artificial polyploids. While a consider3Jble amount of breeding work on autotetraploid sorghum has been carried at Serere, relatively little is known about it from the cytological standpoint. The purpose of this preliminary work was to determine the distribution of quadrivalents in autotetraploid sorghum varieties with a view to initiating a selection programme for regular chromosome behaviour.