Cytogenetic analysis of two interspecific Citrus allotetraploid somatic hybrids and their diploid fusion parents

Abstract

AbstractMicrosporogenesis of two interspecific allotetraploid somatic hybrids, i.e.‘Hamlin’ sweet orange +‘Rough Lemon’ (HR) and ‘Key’ lime +‘Valencia’ sweet orange (KV), was examined and compared with their corresponding diploid fusion parents. Meiotic analysis revealed that only 13.2 and 18.0% of the meiocytes exhibited normal tetrad formation in HR and KV somatic hybrid plants, respectively, and irregular chromosome behaviour with univalent or multivalent pairing occurred. Moreover, meiotic abnormalities such as chromosome bridges, chromosomes orientated away from the equatorial plate, especially lagging chromosomes, which resulted in different sizes of pollen grain, were frequently observed in both somatic hybrids. As expected, the percentage of chromosome abnormalities was much lower in their corresponding diploid fusion parents. HR and KV had 15.4 and 7.2% pollen germinability, respectively, intermediate between their corresponding fusion parents. The meiotic behaviour of these somatic hybrids provided valuable information for their practical utilization in a citrus breeding programme.