GENETIC-VARIATION FOR FOOT ROT AND FUSARIUM HEAD-BLIGHT RESISTANCES AMONG FULL-SIB FAMILIES OF A SELF-INCOMPATIBLE WINTER RYE (SECALE-CEREALE L) POPULATION

The amount of genetic variation for resistance to foot rot caused by P seudocercosporella herpotrichoides, Fusarium spp., and Microdochium ni vale and for resistance to head blight caused by Fusarium culmolum are important parameters when estimating selection gain from recurrent se lection in winter rye. One-hundred and eighty-six full-sib families of the self-incompatible population variety Halo, representing the Petku s gene pool, were tested for foot-rot resistance at five German locati on-year combinations (environments) and for head-blight resistance in three environments with artificial inoculation in all but one environm ent. Foot-rot rating was based on 25 stems per plot scored individuall y on a 1-9 scale. Head-blight resistance was plotwise scored on a 1-9 scale and, additionally, grain-weight per spike was measured relative to the non-inoculated control plots. Significant estimates of genotypi c variance and medium-sized heritabilities (h(2) = 0.51-0.69) were obs erved in the combined analyses for all resistance traits. In four out of five environments, the amount of genetic variance was substantially smaller for foot-rot than for head-blight rating. Considerable enviro nmental effects and significant genotype-environment interactions were found for both foot-rot and head-blight resistance. Coefficients of e rror-corrected correlation among environments were considerably closer than phenotypic correlations. No significant association was found be tween the resistances to both diseases (r = - 0.20 to 0.17). In conclu sion, intra-population improvement by recurrent selection should lead to substantial higher foot-rot and head-blight resistances due to sign ificant quantitative genetic variation within Halo. Selection should b e carried out in several environments. Lack of correlation between foo t-rot and head-blight resistance requires separate infection tests for improving both resistances.