In mature plant breeding programs an elite core germplasm forms the backbone of the breeding effort. A potential problem arises as the gap between the elite core germplasm and donor germplasm widens and germplasm diversity narrows. The objective of this research was to assess the effects of transferring genes from two-row barley (Hordeum vulgare L.) cultivars to a six-row gene pool with primary focus on grain yield. The underlying premise was that the gene combinations in elite six-row cultivars should be largely maintained and the proportion of donor two-row germplasm small. This was tested by conducting three cycles of recurrent-type breeding beginning with crosses involving five two-row donor parents. The crossing scheme led to progenies with theoretical portions of two-row germplasm of 25 to 50% in cycle 1, 12.5 to 25% in cycle 2 and 6.25 to 12.5% in cycle 3. Two-row progeny were only evaluated in cycle 1. In cycle 1, mean yield of the six-row progeny across the five populations was 92% of the respective six-row parent. Kernel weight of cycle 1 two-row lines exceeded their two-rowed parent while kernel weight of six-rowed lines was lower than their six-row parent. In cycle 2, grain yield improved to 98% of the check mean and kernel weight also was substantially improved compared to cycle 1. In cycle 3, sets of lines representing the three populations yielded from 112 to 119% of the check mean in 1997 and 1998 and individual lines surpassed ‘Stander’, the highest yielding check in both 1997 to 1998. The highest yielding lines in each cycle were derived from populations having the highest theoretical percentage of adapted recurrent parent germplasm, i.e., when six-row gene combinations were predominately left intact. Results from the three breeding cycles support the proposition that a strategy that maintains favorable gene combinations while introgressing relatively small amounts of donor germplasm can lead to incremental yield gains.

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