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https://www.ias.ac.in/article/fulltext/jbsc/045/0024

Adjacent-1 segregation; alternate segregation; dikaryon; homokaryon; introgression; translocations; transmission ratio distortion

The ${T(EB4)}^{Nt}a$, ${T(IBj5)}^{Nt}a$, and ${T(B362i)}^{Nt}A$ strains were constructed by introgressing the insertional translocations EB4, IBj5, and B362i from Neurospora crassa into the related species N. tetrasperma. Theprogeny from crosses of ${T(IBj5)}^{Nt}a$ and ${T(B362i)}^{Nt}A$ with opposite mating-type derivatives of the standard N. tetrasperma strain 85 exhibited a unique and unprecedented transmission ratio distortion (TRD) that disfavored homokaryons produced following alternate segregation relative to those produced following adjacent-1 segregation. The TRD was not evident among the [mat A + mat a] dikaryons produced following either segregation. Further, crosses of the ${T(IBj5)}^{Nt}a$ and ${T(B362i)}^{Nt}A$ strains with the Eight spore (E) mutant showed an unusual ascus phenotype called ‘max-4’. We propose that the TRD and the max-4 phenotype are manifestations of the same Bateson-Dobzhansky-Muller incompatibility (BDMI). Since the TRD selects against 2/3 ofthe homokaryotic progeny from each introgression cross, the BDMI would have enriched for the dikaryotic progeny in the viable ascospores, and thus, paradoxically, facilitated the introgressions.

SELVAM REKHA^{1 2} DURGADAS P KASBEKAR¹

1. Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500 039, India
2. Present Address: Laboratory of Medical Genetics, Apollo Main Hospitals, Chennai 600 006, India

Published

30 January 2020