Occurrence of 1BL.1RS wheat-rye chromosome translocation and of Sr36/Pm6 resistance gene cluster in wheat cultivars registered in Hungary

The 1BL.1RS wheat-rye translocation and a wheat-Triticum timopheevii chromosomal introgression carry the Sr31, Lr26, Yr9 and Pm8 genes and the Sr36/Pm6 gene cluster, respectively. The objective of this study was to determine the distribution and impact of these two translocations in 220 wheat varieties registered in Hungary in the last 35 years until 2005. The 1BL.1RS translocation was introduced into Hungary via wheat cultivars 'Avrora' and 'Kavkaz', which were registered in 1970. New 1BL.1RS cultivars developed in Hungary first appeared in 1982. After reaching a maximum frequency of 50.0% among cultivars registered in Hungary in 1994, their presence declined steadily to 13.3% by 2005. The Sr36/Pm6 cultivars first appeared in 1980. Their frequency quickly reached 31.8% (1983-1984), but then dropped to between 9.6 and 18.5% (1990-2005). The two main Hungarian breeding programs showed opposing trends in the exploitation of these two translocations. In Martonvasar, 1BL.1RS played a dominant role, being present from 1993 to 1997 in ca. 95% of the released cultivars, while at the same time the use of Sr36/Pm6 was marginal. Conversely, among the Szeged cultivars, Sr36/Pm6 was present at high frequency (44.7% in 2002) with a low share of 1BL.1RS. In artificial field inoculation tests (1985-2003) both of the stem rust resistance genes provided significant resistance in all the years, though Sr36 proved more effective than Sr31. While Pm8 was not effective, except for the last 2 years, Pm6 exhibited significant resistance against powdery mildew in most of the 18 years tested. These data may help breeders to assess the usefulness of wheat-rye 1BL.1RS chromosome translocations and the Sr36/Pm6 resistance gene clusters in their future wheat improvement programs.