Prospects for hybrid breeding in winter triticale: II. Relationship between parental genetic distance and specific combining ability.

Significant relative midparent heterosis (MPH%) for grain yield in triticale (× Triticosecale Wittm.) has generated interest in the development of hybrid cultivars. The objectives of this study were to (i) examine the association between parental genetic distance (GD) and specific combining ability (SCA), (ii) investigate the existence of genetically distant heterotic groups in elite germplasm, and (iii) draw conclusions for future hybrid breeding in winter triticale. Genetic distance between 61 lines was estimated, based on 93 polymorphic simple sequence repeat (SSR) marker loci and 10 AFLP (amplified fragment length polymorphism) primer-enzyme combinations (PEC). Agronomic data of 206 F1 crosses and their 61 parental lines grown in six German environments were published recently in a companion study. Correlations were made between SCA for grain yield, number of spikes/m2, 1000-kernel weight and number of kernels per spike with GD estimates of the 56 female and five male parents (testers). Principal co-ordinate analyses (PCoA) based on SSR data revealed no distinct subgroups in the germplasm. Correlations between GD and SCA were low for all traits (|r| ≤ 0.31), which hampers the prediction of SCA from molecular data. A multi-stage procedure is recommended for future hybrid breeding in triticale by applying a pragmatic approach for the grouping of germplasm following the early history of hybrid breeding of maize. [ABSTRACT FROM AUTHOR]