CYCLIC BREEDING USED TO INCORPORATE KERNEL DISCOLORATION RESISTANCE INTO MALTING BARLEY

Obtaining kernel discoloration (KD) resistance in malting barley (Hordeum vulgare L.) is an important breeding objective in the midwestern USA. This study was undertaken to evaluate a cyclic breeding procedure for transferring quantitative KD resistance across a wide genetic gap, and to obtain parental germplasm or a new cultivar having KD resistance combined with good agronomic performance and malting quality. Six cycles of crossing and selection were done beginning in 1970 to incorporate KD resistance genes from 'Chevron' and CI 9539 into Minnesota barley lines. Chevron and CI 9539 were inferior for both agronomic and quality traits. Subsequently, 45 sixth-cycle derived lines were evaluated in inoculated disease nurseries and in field trials to determine whether resistance was transferred and to assess agronomic and malting quality merit. Kernel discoloration resistance was successfully transferred using the cyclic breeding procedure, although the resistance level tended to be below that of the resistance sources. The derived lines were similar to the local cultivars Robust and Morex for agronomic and quality traits, except for kernel plumpness, and to a lesser degree malt extract. They showed marked overall improvement compared with the resistance sources, Chevron and CI 9534, and a few of the lines merit consideration as potential cultivars. Unconscious selection was hypothesized to account for the intermediate level of KD resistance observed in local germplasm. In this situation, cyclic recurrent breeding appeared to be a good choice for incorporating a quantitative disease trait into a good genetic background.