Yield‐component Analysis of Oat Isolines that Produce Different Grain Yields 1

A series of early and midseason isolines of oats ( Avena sativa L.) contain specific crown‐rust resistance loci, which were associated with significant grain‐yield deviations when tested in rust‐free conditions. To delineate specific causes for these yield deviations, yield components were measured in the isolines and their recurrent parents in six rust‐free environments. Increased grain yields in both isolines with the crownrust resistance allele from CI 8079, an Avena sterilis L. strain from Israel, were due primarily to significantly increased tiller production. A 3.0% increase in spikelets per panicle also contributed to the increased yield of CI 9170, the early‐maturing isoline. Although each donor parent was associated with contrasting yield‐component expressions in the early and midseason backgrounds in the remaining isoline sets, causes of deviant yields were evident. An increase in panicle number contributed to grain‐yield advantages of isolines derived from CI 7171, while seed weight improvement was the most important contributor to yield improvement in the midseason isoline. The significant yield reductions of X5501 and CI 9192, the early and midseason isolines with crown‐rust resistance derived from Arena strigosa Schreb., were caused primarily by fewer spikelets per panicle.