Chromosome Numbers of Crop Species*

Abstract

The number of chromosomes is one of the factors that can have a powerful influence on recombination. An organism with the haploid number of n, and heterozygous for one gene pair on each chromosome pair, can produce 2n genetically different gametes. Knowledge of the chromosome number of all the species of a genus or family can help determine the basic chromosome number of the genus or family. If the crop species deviates from this, it can be determined if the basic chromosome number has changed by aneuploidy or polyploidy. Knowledge of the chromosome number makes the analysis of chromosome pairing much easier. In species with small chromosomes, and in particular polyploids and F, hybrids, it is almost essential. Complex pairing configurations can often not be interpreted accurately without prior knowledge of the number of somatic chromosomes.