Effectiveness of Stripe Rust Resistance among Lemhi 53 Spring Wheat Near‐Isogenic Lines 1

Stripe rust (caused by Puccinia striiformis West.) is a major wheat ( Triticum aestivum L.) disease in the northwestern USA, and resistance offers the most economic control. This study compared the effectiveness of ‘Lemhi 53’ type near‐isogenic lines that derived stripe rust resistance from 13 diverse sources. Factors considered were grain yield capacity of triadimefon‐treated [l‐(4‐chiorophenoxy)‐3,3‐dimethyl‐l‐(IH‐1,2,4‐triazol‐1‐yl)‐2‐butanonel and untreated plots, percent yield loss, backcross number, stripe rust reaction type, and severity ratings. Pooled mean yields from treated and untreated plots across 1981 and 1982 trials were compared and used to determine percent yield loss due to stripe rust. Lines with similar stripe rust reaction types, both among and within families, varied for yield potential, with and without fungicide, percent yield loss, or both. Lines of families with resistant, moderately resistant, or intermediate stripe rust reaction types proved most useful in preventing grain yield losses. However, certain lines of all stripe rust reaction classes, excepthe susceptible class, had negligible losses. Low inherent yield potential was associated with increased backcross number and combined leaf and stripe rust resistance. In general, subjective ratings of stripe rust reaction type and severity complemented evaluation of the germplasm, but they did not always identify lines with low yield loss and high yield potential. Five lines from different families exhibited high yield potential under stripe rust attack and had yield losses of only 2 to 7%.