Incidence variability of wheat bunts (Tilletia caries (DC) Tul. and T. laevis Kühn) in field trials

Until now, the wheat resistance against common bunt disease (Tilletia sp.) has been studied by most authors in field trials without replications. It was supposed that using 1 g spores per kg seed the inoculum was sufficient for regular infection. In our preliminary field trials with selected winter wheat cuhivars inoculated with common bunt, considerable variability was observed in some cases in replications. The reasons for this variability was studied in laboratory and field trials. The incidence of common bunt is influenced, first of all, by the sowing date and the soil temperature at the time of wheat germination. The germination of spores is adversely influenced by superfluous water in the environment. Some antagonistic micro-organisms can decrease the spore germination and in this way decrease the disease incidence. In 1998, we studied the variability of wheat resistance against common bunt in 32 winter wheat cultivars in replications. The aim was to propose a number of replications and a number of scored ears. It was found that replications without disease incidence appeared in groups and they were higher in the case of higher resistance. No correlation was found between the spore amount in the range from 1 to 10 g spores per kg seed and disease incidence. A good correlation was found between susceptibility of all cultivars to both bunts. To assess wheat resistance to common bunt, the following rules should be kept: 1) at least 1 g spores per kg seed. 2) four plot replications situated in different parts of field, 3) scoring 100-150 ears. 4) repetitions in different years.