Experiments on vegetative dissociation of the dikaryon and on lysis of hybrid sporidia of the cross Ustilago avenae × U. kolleri

Abstract

Disintegration of the nucleus of Ustilago avenae at vegetative dissociation of the interspecific dikaryon U. avenae × U. kolleri, as well as lysis of the sporidia formed by hybrid spores of the same cross, are caused by suppressive interaction between a number of nuclear genes. Lysis can be partly prevented by subjecting the hybrid primary sporidia to temperatures between 25 °C and 40 °C. The higher the temperature the shorter the time required to induce subsequent continued growth at 20 °C. As lysis is confined to the haploid stage, it is not an effective barrier against production and propagation of hybrids between these smut species in nature, so that advantageous genes will continue to combine, disadvantageous ones will disappear.