Cytology of backcross four individuals derived from a saccharum-sorghum hybrid

Abstract

The intergeneric hybrid between sugarcane (Saccharum officinarum L.) and sorghum (Sorghum bicolor (L.) Moench) was produced by pollinating sugarcane inflorescences with sorghum pollen. The BG population, produced by backcrossing twice with diploid (2”=20) and then twice with tetraploid (2”=40) sorgo, probably combined 40 Sorghum and 4-10 Saccharum chromosomes. The cytological observations suggest that different combinations of sugarcane and sorghum chromosomes are retained in different BG individuals. The sugarcane chromosomes either associate loosely with sorghum bivalents and/or tetravalents or pair autosyndetically. The sorghum chromosomes do not behave as in normal sorghum in the presence of sugarcane chromosomes and cytoplasm. Cytological studies of Saccharum- Sorghum hybrid derivatives suggest that interaction between their genomes can take place. Selling of these BG plants results in almost complete elimination of Saccharum chromosomes, and morphologically and cytologically modified tetraploid sorghums with In=40 chromosomes are recovered. Presence of high valency configurations in BG and in selfed offspring of BG individuals seems to indicate that intergenomic genetic exchange between sugarcane and sorghum may have taken place in earlier backcross generations, but it has not been confirmed by this study. © 1990, Taylor and Francis Group, LLC.