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Factors Affecting Infection of Wheat Seedlings by Septoria nodorum. M. Babadoost, Graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650; T. T. Hebert, professor emeritus, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 74:592-595. Accepted for publication 5 December 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-592.

Coleoptile infection of wheat by Septoria nodorum occurred over broad ranges of soil moisture, temperature, and planting depth. Increased frequency of watering significantly reduced the severity of the disease in seedlings. However, low soil water potentials, obtained by equilibration with polyethylene glycol solutions through dialysis membranes, did not enhance disease development. Seedlings became infected at temperatures of 10, 15, and 20 C in growth chambers. Sowing depths of 2.5, 5, and 7.5 cm in a gravel Peat-lite medium did not significantly affect seedling infection. There was a close positive correlation between percent seed infection and percent diseased seedlings. Increasing the concentration of the spore suspension used to inoculate the seed, from 103 to 106 spores per milliliter, increased percent seedling infection from 90 to 100%. Furthermore, high inoculum density on seeds resulted in more diseased and more severely diseased coleoptiles. Disease severity of seedlings increased until 4 wk after sowing.

Additional keywords: epidemiology, glume blotch, Leptosphaeria nodorum, Triticum aestivum.