Meiotic chromosome behaviour and Boronia (Rutaceae) genome reorganisation

Abstract

Meiotic observation of nine genotypes of seven Boronia Sm. species revealed that B. megastigma Bartling (2n = 14), B. molloyae J.R.Drumm. (2n = 16), B. purdieana Diels (2n = 18), B. pinnata Sm. (2n = 22) and B. chartacea P.H.Weston (2n = 32) behaved as diploids during meiosis. B. coerulescens F.Muell. (2n = 72) was a tetraploid. These species had normal homologous chromosome pairing and segregation during meiosis and high pollen viability of 82–99%. Base chromosome numbers for B. megastigma, B. molloyae, B. purdieana, B. pinnata, B. chartacea and B. coerulescens were 7, 8, 9, 11, 16 and 18, respectively. Irregularities were found in meiosis of B. heterophylla F.Muell., which had low pollen viability of 43–46%. Results indicated that chromosome number in B. heterophylla might be the result of dysploid reduction or aneuploid reduction with 'Red' a monosomic, whereas 'Cameo' and 'Moonglow' were double monosomics. Boronia genome appeared volatile and genome repatterning in Boronia is still occurring.