YIELD STABILITY IN FABA BEAN, VICIA-FABA L .2. EFFECTS OF HETEROZYGOSITY AND HETEROGENEITY

In order to evaluate the effects of heterogeneity and heterozygosity o n yield stability in faba beans, genotypes were generated with contras ting population structures, differing only in their levels of heteroge neity and heterozygosity. All entries were based on either eight or 36 inbred lines, respectively The population structures tested consisted of pure stands of the inbred lines (1) and of their F1-hybrid (2), bl ends of the inbred lines (3) and of their F1 hybrids (4), four-compone nt synthetics in different Syn-generations (5), the open-pollinated so urce varieties (6) and 36 polycross progenies (7). Five different ent entry sets (= data sets), each covering several of the seven populatio n structures listed, were grown during 1986 to 1991 in at least four d ifferent environments in Western Germany and tested for yield. Stabili ty parameters, i.e., the regression coefficient and deviation from reg ression (EBERHART and RuSSELL 1966), and the ecovalence (WRICKE 1962), revealed that yield stability of the different population structures was improved by increasing heterozygosity as well as heterogeneity. Bu t the impact of both factors of diversity on yield stability varied be tween the different data sets. Positive effects of both factors on yie ld stability seemed to be additively combined in the hybrid blends (da ta set 1). The same proved to be partly true for the four different Sy n-generations of the nine synthetics tested. Yield advantage of the di fferent heterozygous variety structures over the homozygous ones incre ased with increasing yield level at test sites, as indicated by regres sion coefficients larger than 1.