Organic farming has gained in importance in Germany during recent years. Therefore an increasing demand exists for varieties with specific adaptation to this farming system. In the present study we therefore conducted comparative field experiments with modern maize breeding materials under organic versus conventional farming conditions (ORG and CON, respectively) to estimate quantitative genetic parameters needed for developing optimal breeding strategies and to investigate the perspectives of selection for specific adaptation to ORG. Starting from two broad samples of elite germplasm, consisting of 178 flint and dent lines, respectively, fractions of 11 flint and 11 dent lines were selected based on their testcross performance under ORG. A corresponding set of lines was selected under CON. Testcross performance was evaluated in three regions of Germany and selection of superior lines was practiced across two stages in 2004 and 2005, respectively. The specifically selected lines were crossed in a factorial manner for production of experimental interpool single-cross hybrids which were field-tested under ORG and CON in two regions in 2006. Average grain yields were about 16% lower under ORG than under CON. Variance components and entry-mean heritability coefficients under ORG largely resembled those obtained under CON. Phenotypic correlations between ORG and CON were moderate for grain yield and strong for grain dry matter content. No consistent estimates were obtained for the corresponding genotypic correlation for grain yield. At the first stage of testcross selection no evidence of specific adaptation to ORG or CON was observed whereas the factorial crosses tested in 2006 displayed distinct, yet non-significant, advantages when evaluated under the respective target farming system. A small top fraction of hybrids showed outstanding performance under both ORG and CON. The chances of detecting such broadly adapted genotypes are increased if ORG test sites are included in the regular testing system.

In maize (Zea mays L.), as in other cross-pollinated crops, a high mutational load of deleterious recessive alleles hampers the use of landraces in hybrid breeding. The in vivo doubled haploid (DH) technology meanwhile offers great promise in purging such alleles. This approach was employed to three European flint type landraces. Eighty DH lines were evaluated for testcross performance under three farming conditions. Mean testcross performance of DH lines was similar to that of their parental landraces but 22-26% lower than that of present elite flint lines. Highly significant genetic variance existed in each of the three DH-line groups. Coefficients of genetic variation ranged from 6.7 to 7.4. DH-lines derived from ÔLucq de Be´arnÕ displayed specific adaptation to N deficiency. The 10% (out of 80) best DH lines surpassed the first-cycle lines by 11% in testcross grain yield and remained only 13% below the elite lines. Altogether, the DH approach proved to be a highly effective tool for gaining access to the hitherto hardly tapped broad genetic diversity of landraces in research and breeding.

Hybrid breeding is a widely discussed alternative for triticale. Heterosis as well as general (GCA) and specific combining ability (SCA) effects were estimated for eight agronomic traits. The experiment comprised 24 F1 hybrids, produced by a chemical hybridizing agent, together with their six female and four male parents, grown in drilled plots in two locations. In comparison with the mid‐parent values, hybrids averaged a 6.4 dt/ha (10.1%) higher grain yield, 8.4% more kernels per spike, a 6.8% higher 1000‐kernel weight, 9.7% lower falling number (FN) and 4.4% greater plant height. SCA effects for grain yield were significant and ranged from 4.5 to 6.9 dt/ha for grain yield. Together with GCA x location interactions, they explained most of the variation. For 1000‐kernel weight, GCA effects were predominant. SCA and interactions with location accounted for most of the variation in FN, whereas interactions were negligible for plant height. Correlations between mid‐parent and hybrid performance and between GCA and per se performance of parents were tight for all traits except grain yield, which allows for pre‐selection of parental lines. Although the amount of heterosis in triticale at present is closer to wheat than to rye, by selecting parents for combining ability and identifying heterotic patterns, grain yield heterosis of up to 20% appears sufficiently encouraging to embark on hybrid breeding.