VARIATION AND COVARIATION OF AGRONOMIC TRAITS AND QUALITY IN TRITICALE AT LOW NITROGEN INPUT

The use of high nitrogen (N) inputs is becoming restricted in many cou ntries due to environmental and economic considerations and reliable i nformation is needed about parameters pertinent for breeding N-use eff icient triticales (xTriticosecale Wittmack). This study reports estima tes of variances, heritabilities, correlations, and regression for 36 triticales, grown at three locations for 2 years with two N regimes (z ero and normal N supply). Eleven traits were assessed. A 45% mean redu ction in grain yield by low N input was mainly the result of a 25% low er number of tiller-bearing spikes per m(2) and 17% fewer kernels per spike, whereas 1000-kernel weight was little affected. Genotype-nitrog en interaction was of importance only in some environments and for cer tain traits. Heritability estimates at both N levels were similar and moderate to high. Correlations between N levels were high for nearly a ll traits. Regression analysis for grain yield revealed only few N-eff icient triticales with lower than unity slope together with a high gra in yield. Based on the genetic parameters, it is concluded that a spec ial low input breeding programme does not appear to be necessary in tr iticale. The breeder can select at either of the N levels with similar response. But he should include tests in low productivity environment s at some early stages in the breeding process to avoid loss of geneti c variation for N-use efficiency.