Chromosome studies in some Actinidia taxa and implications for breeding

Microsporogenesis was studied in eleven Actinidia taxa including A. deliciosa (kiwifruit) and in an interspecific hybrid. From chromosome counts at meiotic metaphase 1 or diakinesis, eight taxa were classified as diploids and two as tetraploids and A. deliciosa was confirmed as hexaploid. A putative 2 n = 2 x , 2 n = 4 x , 2 n = 6 x , x = 29 basis for the genus is therefore supported. Chromosomes in all taxa were very small. Three diploids and two polyploids analysed for meiotic pairing behaviour were all characterised by low chiasma frequencies per bivalent. Chromosome configurations other than bivalents were rare in A. arguta var. arguta (4 x ) and A. deliciosa (6 x ), indicating there may be genetic control of chiasmata distribution in these polyploids.