Seventeen hundred‐twenty selections of winter wheat (Triticurn aestivum L. em Thell.) were screened for tolerance to the barley yellow dwarf virus (BYDV), and the effects of fall and spring BYDV infections on several traits were investigated in different years. Fall infection was more damaging than spring infection for all traits measured except kernel weight and harvest index where spring infection caused more severe reductions. Grain yield was reduced an average of 63% for fall, and 41% for spring infections. No outstanding sources of tolerance were discovered, though some entries were more tolerant than others. Several alloplold derivatives from crosses of winter wheat with tall wheatgrass [Agropyron elongatum (Host) Beauv.] were highly tolerant. A significant interaction of selections with date of inoculation indicated differential response of some entries to fall and spring infections. Some selections were tolerant regardless of the time of infection. The relationship between visual disease severity ratings and plant damage as measured by yield of infected plots as percentage of control plots was sufficiently strong (r = 0.65) to ensure genetic advance toward reduced yield loss by selection based on visual assessment of disease severity.
More than 2,200 samples of the wild oat (Avena fatua L.) were collected from western North Central U.S. as part of a program to preserve natural variant populations of this species and to further evaluate its potential as a germplasm source for the improvement of cultivated oats (A. sativa L.). This report summarizes the results of screening these samples for tolerance to barley yellow dwarf virus (BYDV), resistance to cereal leaf beetle (Oulema melanopus L.), and resistance to oat stem rust (Puccinia graminis Pers. f. sp. avenae Eriks. and E. Henn.), plus analyses of groat protein and amino acid composition.High level tolerance to BYDV was identified in 34 of 483 samples tested. Tolerance appeared to be more frequent among samples collected in areas with a higher incidence of disease. Low level resistance to cereal leaf beetle was observed in 20 of 400 samples. The occurrence of resistance was unrelated to the incidence of the beetle. No resistance to the highly virulent race 94 of oat stem rust was identified in more than 1,600 samples tested. Groat protein levels ranging from 16.7 to 27.1% were observed among 723 A. fatua samples analyzed, whereas amino acid profiles of 70 A. fatua samples tested were similar to those reported for cultivated oats. The A. fatua collection described in this report not only provides potential new sources of BYDV tolerance and high groat protein percentage but also constitutes a valuable germplasm reservoir.
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