'Plant Breeding: Sustaining the Future' Abstracts of the XVIth EUCARPIA Congress, Edinburgh, Scotland, 10-14 September 2001 ASSOCIATIONS BETWEEN HEADING DATE OR PLANT HEIGHT AND RESISTANCE TO SEPTORIA TRITICI BLOTCH IN THE ADULT STAGE OF WHEAT M.R. SIMON, A.E. PERELLO, C. ACORDO, S. LARRAN, F. MAYALA, D. BAYO, P.C. STRUIK Cerealicultura. Facultad de Cs. Agrarias y Forestales, U.N. La Plata. CC 31. 1900 La Plata, Argentina

Negative associations between heading date and plant height of wheat cultivars with resistance to Septoria tritici Rob. ex Desm. (teleomorph Mycosphaerella graminicola (Fuckel) Schroeter, in Cohn) have been attributed to genetic linkage between traits or to escape to the disease. Two field experiments were conducted near La Plata, Argentina including 50 Argentinean cultivars differing in heading date and height. Plants were inoculated at GS12 and GS14, Zadoks et al., 1974. Disease severity was assessed when each cultivar reached GS49, GS70 and GS83. During 1998 weather conditions were more favourable for the disease at the beginning of adult evaluations of early cultivars. This caused a negative significant association between heading date and severity at GS49 and GS70 but no association at GS83. AUDPC was also negative correlated with heading date. Height to flag leaf was negatively associated with severity at GS83 and with the AUDPC. In 2000, weather conditions were in general more conducive for the disease and similar for early and late cultivars. No significant correlations between heading date and disease severity at any stage or AUDPC were found. Height to flag leaf was not correlated with disease severity or progress either. In this set of cultivars there is no evidence of genetic associations between early heading and susceptibility to the disease. Such associations depend on weather conditions. Negative associations with height to flag leaf were lost when weather conditions were more conducive.