3.4.41
BREEDING FOR RESISTANCE AGAINST LEAF DISEASES IN WINTER WHEAT

M CSOSZ, J MATUZ, Z KERTFTSZ, A MESTERHAZHY and Z BARABAS

Cereal Research non profit Company, 6701 Szeged, POB 391, Hungary

Background and objectives
The resistance against diseases has been an important goal of breeding up to now. In the past decades (1970-97) different research has been conducted in this field, the most important results of which are summarized here.

Results and conclusions
Tolerance has been a significant part of the work. The center pivot design (50 m long plots) allowed to identify tolerant genotypes for stem rust [1], a modified design (20 m long plots) led to the same results. It could be proved that 2 m2 plots give the same information, as the most important changes occur on the first 2 m part of the plots. The methodical development and the identification of tolerant genotypes over the years have proved the presence and usefulness of tolerance in breeding. Additionally, epidemiological insights were gained: the spreading speed of the disease correlated very closely (above r=0.95, P=0.1) with the disease severity recorded at the spreader. This technique is suitable to measure tolerance in homogenous genotypes; breeding for tolerance on individual plant basis is a task still to be solved.

The influence of stem rust resistance was studied on the expression of the 1000 grain mass heredity. 9 cultivars with differing resistance were examined in a half diallel design with 36 crosses. According to the Griffith diallel analysis model, mostly additive gene actions were recorded. As the test was made under infected and protected environments, the inheritance of the 1000 kernel mass reaction could be compared. The test has shown that inheritance studies for 1000 kernel mass should be done in disease free trials. In GK Mini Mano, however, a strong gene was found that secured in all crosses immunity or a very low disease severity [2].

The cultivar GK Kincs6 was tested under field conditions using artificial inoculation for stem rust since 1979. The stem rust resistance remained stable throughout that period, therefore its resistance could be considered as durable. Its mildew reaction from natural epidemics was also recorded. During the first 10 years it was nearly symptomless. Later on an increase in disease severity was observed. However, the last years gave again lower incidences. As in this time the rare structure changed 3-4 times we conclude that also the powdery mildew resistance seems to be stable.

As GK Mini Man6 and GK Kincso carry according to the pedigree the stem rust resistance gene Sr36, a test was carried out to identify this gene. Crosses and backcrosses, F2 and F3 populations were analyzed in the field and in seedling stage, and proved the presence of this gene. GK Kincso was extensively used in our breeding program and until now the new and resistant cultivars GK Gobe, GK Zugoly, GK Kalasz, GK Voka, GK Szindbad, and several perspective candidates as GK Garaboly, GK Divid, GK Kunsag, GK Jaszag.

The authors are indebted to scientific grants OTKA 17453 and OMFB 4054 for the support of this work. For the inoculum used in the Szeged trials we express our thanks to Dr Klara Manninger, PPI, Budapest.

References
1. Matuz J, Mesterhazy A, Barabas Z, 1979. Theor. Appl. Gene. 55, 199-204.
2. Csosz M, Kertosz Z, Matuz J, Barabas Z, 1995. Cereal Res. Comm. 23, 133-140.