Yielding Ability of Pure Stands and Equal Proportion Blends of Rapeseed (Brassica napus L.) with Double-low Quality

Yielding ability of intraspecific mixtures is an important issue not only for homozygous and homogeneous crops but also for heterozygous and/or heterogeneous ones. The goal of the present study was to examine the performance of mixtures and synthetics from double-low (low in erucic acid and glucosinolates) rapeseed ( Brassica napus L.) as compared to pure stands. The material consisted of seven lines and from 1982/83 to 1984/ 85 lines, all possible biblends and syn₁'s (1983/84 and 1984/85 exclusively) were grown in a completely randomized block design. An analysis of variance was conducted and general mixing effects (g.m.e.) and specific mixing effects (s.m.e.) were calculated for components of biblends. A few pure-standing lines yielded higher than some mixtures. Nevertheless, the overall mean of mixtures was not exceeded by any pure stand. For selection purposes, the higher variance of 'among lines' in comparison with 'among blends' would not result in higher yields because of the generally higher yielding ability of blends. Additionally, mixtures were marked by higher yield stability as compared to pure-standing lines. On the average of two years of testing yields of syn₁'s amounted higher than yields of mixtures. Differences between 'g.m.e.' of lines were proved and moreover, the variance component of 's.m.e.' was on a lower level than that of 'g.m.e.'. Consequently, in order to find the best mixture it seemed not necessary to analyse a complete diallel rather than to apply factorial or incomplete factorial concepts.