Factors Affecting Seedling Emergence of Sorghum for Short-Season Areas. D. A. Gaudet, Plant Pathologist, Research Station, Agriculture Canada, Lethbridge, Alberta T1J 4B1. D. J. Major, Crop Physiologist, Research Station, Agriculture Canada, Lethbridge, Alberta T1J 4B1. Plant Dis. 70:572-575. Accepted for publication 5 December 1985. Copyright 1986 Department of Agriculture, Government of Canada. DOI: 10.1094/PD-70-572.

The potential for extending the range of sorghum (Sorghum bicolor) into southern Alberta depends on improving the percentage of seedling emergence. Studies were done to examine the effect of rooting medium and ambient temperature on percentage of emergence, to determine the part played by soilborne and seedborne pathogens in reducing emergence, and to identify pathogens that might be important in southern Alberta. Increased impedance in the rooting medium decreased percentage of emergence as did low temperatures, which increased the pathogenicity of seedborne and soilborne fungi. Penicillium oxalicum, Aspergillus spp., and a Rhizopus sp. were prevalent in seed lots produced in southern Alberta and Texas, but poor seed viability and stunting of the roots of coleoptiles could be attributed only partially to seedborne fungi. Two Fusarium spp., F. oxysporum and F. tricinctum, isolated from Alberta soils were pathogenic to sorghum at low temperatures. Chilling injury per se was not the cause of reduced emergence, and stresses caused by low temperatures or heavy soils enhanced the pathogenicity of soilborne and seedborne pathogens.