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Development and Nuclear History of the Teliospores of Urocystis colchici. R. L. Grayson, Biological Sciences Department, California Polytechnic State University, San Luis Obispo 93407; M. L. Lacy, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Phytopathology 65:994-999. Accepted for publication 1 April 1975. DOI: 10.1094/Phyto-65-994.

Development and nuclear history of the teliospores of Urocytis colchici were studied in infected onion seedlings by employing light- and electron microscope techniques. Teliospores developed from terminal cells of sporogenous hyphal branches which curved back upon themselves, and surrounding hyphal cells became appendage cells of the teliospores. Both appendage cells and central spores of young teliospores were dikaryotic initially, but central spore nuclei underwent karyogamy and became diploid before maturity. Appendage cells, initially binucleate, appeared to become mononucleate by disintegration of one of the nuclei. Nucleoli were evident in both haploid and diploid nuclei. Central spore walls differentiated into three distinct layers. Appendage cells contained organelles similar to those found in central spores, but contained fewer lipid bodies. Appendage cell walls had only two distinguishable layers, and were attached to the central spore wall by an amorphous matrix. Only appendage cells germinated when freshly collected teliospores were plated on artificial media.

Additional keywords: Ultrastructure of fungi, onion smut, fungal spore morphogenesis.