A novel meiotic drive in Neurospora crosses heterozygous for hybrid translocation strains disfavors homokaryotic progeny derived from alternate, but not adjacent-1 segregation

Four insertional or quasiterminal translocations ( T ) were recently introgressed from Neurospora crassa into N. tetrasperma . Crosses of two of the resulting T Nt strains with N. tetrasperma N strains ( N = normal sequence) produced more Dp than T and N homokaryotic progeny, although [ T + N ] and [ Dp + Df ] heterokaryotic progeny were made in roughly equal numbers. The T , N , and [ T + N ] progeny are derived from alternate segregation (ALT), whereas adjacent-1 segregation (ADJ) generates the Dp , Df , and [ Dp + Df ] types. Differential recovery of homokaryotic products from ALT and ADJ represents a novel and unprecedented type of meiotic drive. This drive contributed to our inability to introgress a larger insertions translocation, T ( VR > VIL ) UK3-41 , into N. tetrasperma. We suggest that one or more Bateson-Dobzhansky-Muller type incompatibility between N. crassa and N. tetrasperma genes in the T Nt x N crosses might cause an insufficiency for a product required for ascospore maturation. Since the Df type is inviable, only four ascospores ( Dp or [ Dp + Df ] types) share this limited resource in [ Dp + Df ] asci, whereas four to eight ascospores compete for it in [ T + N ] asci. This increases the chance that in asci with >4 ascospores none properly matures, and results in Dp progeny out-numbering T and N types.