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Inheritance in Cochliobolus sativus. R. M. Hosford, Jr., Associate Professor, Department of Plant Pathology, North Dakota State University, Fargo 58102; G. R. M. Solangi(2), and R. L. Kiesling(3). (2)Assistant Plant Pathologist, Agricultural Research Station Dokri in Pakistan; (3)Professor, Department of Plant Pathology, North Dakota State University, Fargo 58102. Phytopathology 65:699-703. Accepted for publication 28 January 1975. DOI: 10.1094/Phyto-65-699.

Cochliobolus sativus was single-spored from asci by a feather needle technique and analyzed for genetic systems using tetrad analysis and randomly isolated ascospores. Segregation for mating type was regular and controlled by one gene. In the tetrad analysis of eight asci, colony color, colony size, and conidial production were each additive and controlled by at least two genes. Additional modifiers of the above traits were detected. Virulence to spring wheat, durum, and barley was controlled by at least two genes which were associated with dark colony color. Genes for virulence separated from genes for dark color by apparent crossing over, and were epistatic over genes for avirulence. In concurrent studies, using 200 randomly isolated ascospores, two genes were associated with virulence to spring wheat and durum, and three to four genes with virulence to barley. Sexual reproduction was prevented in progeny from one cross by a pre-crozier block (controlled by three genes), a post-crozier block, and a preascospore block. White and red strains of the fungus developed from sectors in black colonies from single ascospores. Red strains did not reproduce sexually. Varying sexual fertility, virulence and avirulence, and both mating types were found in several parts of North America.

Additional keywords: Helminthosporium sativum, Drechslera sativus, Bipolaris sorokinianum.