Effect of common bunt on the frost resistance and winter hardiness of wheat (Triticum aestivum L.) lines containing Bt genes

In order to determine the effects of bunt inoculation on frost resistance a nd winter hardiness in lines containing resistance genes, the bunt [Tilleti a foetida (Wallroth) Liro, T. caries (DC.) Tulasne] susceptibility of wheat lines containing bunt resistance genes Bt1 to Bt10 and the effect of the y ear on the degree of infection were studied over six years from 1991 to 199 7 in an artificial inoculation nursery. Uninoculated and artificially inocu lated wheat plants were tested for frost resistance in the phytotron in 199 5 and in the field in boxes in three years from 1994/95 to 1996/97. The lin e with Bt10 was very resistant, lines with Bt5, Bt6, Bt8 and Bt9 were resis tant, the line with Bt4 was moderately resistant, those with Bt2 and Bt3 we re moderately susceptible, the line with Bt1 was susceptible and the line w ith Bt7 was very susceptible to the local bunt population in Hungary. Bunt incidence also varied over years. The frost resistance of the Bt lines was generally lower after bunt inoculation than that of uninoculated plants. Th e increased frost kill in inoculated plants was not correlated with the ext ent of varietal susceptibility to bunt. Some lines with resistance, namely those with Bt5 (1.6% infection), Bt8 (0.6%) and Bt10 (0.0%), suffered signi ficantly greater frost kill in the young plant stage as the result of bunt inoculation. By contrast, the Bt7 line had excellent frost resistance and w inter hardiness but suffered the greatest extent of bunt infection, whereas the Bt6 line had good frost resistance and good bunt resistance.