EFFECT OF BUNT INFECTION ON THE FROST-RESISTANCE OF WHEAT-VARIETIES AND OF LINES CONTAINING BT GENES

In artificial infection experiments carried out in the nursery in Mart onvasar in 1991, 1992 and 1993, studies were made on the bunt infectio n of wheat varieties bred in Martonvasar and of monogenic lines contai ning known resistance genes (Bt1 to Bt10, respectively). This was foll owed in 1993 by tests on the frost resistance of healthy wheat seedlin gs and wheat seedlings artificially infected with bunt in the frost-te sting chamber of the Martonvasar phytotron. During the period of the e xperiment, the local pathogen population was avirulent to genes Bt9 an d Bt10, and virulent to Bt7. Monogenic lines containing resistance gen es Bt4, Bt5, Bt6 and Bt8 had good resistance, while that of lines cont aining Bt1, Bt2 and Bt3 was only moderate. Among the cultivated variet ies, only three proved to be moderately resistant ('Martonvasari 17',' Martonvasari 23', 'Fatima 2'), while the remainder were susceptible or very susceptible. The frost resistance of plants infected with bunt w as significantly lower, over an average of the varieties, than that of healthy plants. A close (r = 0.890) correlation was found between the bunt susceptibility of the varieties tested and the increase in frost kill due to infection, while no correlation was observed in this resp ect for monogenic lines containing various resistance genes (Bt).