Phenotypic Stability of Mixtures – Relations Between the Stability Parameters of a Mixture and Its Components

Abstract

For each of the two stability parametere ('regreasion coefficient' and 'sum of squared deviatiom from the regression') of the common regreasion approach ( = r e g m i o n of the yield of population i in environment j on the environmental index of this evironment j which often has been estimated by the mean of all tested populatione in this environment j) the phenotypic stability of a mixture and it's components have been analyeed theoretically. It can be shown that in practical applicationa (for example: variety teeting) the regression coefficient of a mixture often can be sufficiently approximated by the arithmetic mean of the regression coefficients of the componentg grown singly. This simple relation between a mixture and it's components don't hold for the second stability parameter 'sum of squared deviations from the regression'. The exact relation has been deduced and useful and clear approximations are discussed. All the theoretical resulta are demonstrated and applied using the well-known experimental barley data of SANDFAEB (1970).

Aspekte nachhaltiger Züchtung

“…Funktionen der Umwelt Betrachtet man die Bedeutung der Umwelt im Zusammenhang mit Responsfunktionen, so sind grundsätzlich zwei Funktionen zu unterscheiden: modifizierend und adaptiv (Cavalli-Sforza, 1974;Moran, 1992;Gregorius, 1994;Gregorius und Kleinschmit, 1999) (Hattemer et al, 1982;Gregorius, 1983;Hühn, 1987;Bishir und Roberds, 1999). Damit genügend genetische Hintergrundvariation erhalten bleiben kann, darf die Züchtungspopulation nicht zu klein sein (Stern, 1972;Wellendorf, 1979)…”