Effect of inbreeding and selection for vigour and fertility on meiotic behaviour in autotetraploid job's tears, Coix lacryma-jobi L.

Abstract

Meiotic behaviour of the colchicine-induced "raw" autotetraploid (4n = 40) Job's tears (Coix lacryma-jobi L.) was compared with that of the tetraploid envolved from it through selection for vigour and fertility over a 4 year period and selfing of the selected plants for 3 generations. A significant decrease in quadrivalent frequency and an increase in bivalent frequency per cell, greater frequency of ring quadrivalents, more cells with regular separation of chromosomes and fewer cells with laggards at anaphase I, fewer irregularities in meiosis II, fewer pollen quartets with micronuclei and fewer aneuploids in the progenies were found in evolved tetraploid. The average chiasma frequency per cell, per quadrivalent and per bivalent were more or less the same in both tetraploids. All these facts indicate that inbreeding and selection for vigour and fertility have brought about a shift towards regular meiosis in the evolved tetraploid. The increase in fertility during the period of selection was not, however, significant, suggesting that its response to selection is slow, that a number of factors are probably involved and that, besides multivalents, genic factors also govern sterility in the tetraploid.