• Genetic Differences in Resistance of Range Grasses to the Bluegrass Billbug, Sphenophorus Parvulus (Coleoptera: Curculionidae)

      Asay, K. H.; Hansen, J. D.; Haws, B. A.; Currie, P. O. (Society for Range Management, 1983-11-01)
      Significant differences in plant resistance to larvae of the bluegrass billbug, Sphenophorus parvulus Gyllenhal (Coleoptera: Curculionidae), were found among and within range grass species and interspecific hybrids in nurseries at the Decker, Mont., surface mine and on a site near Miles City, Mont. Slender wheatgrass (Elymus trachycaulus) and related species were particularly susceptible. Crested wheatgrass (Agropyron cristatum and A. desertorum), thickspike wheatgrass (E. lanceolatus), Russian wildrye (Psathyrostachys juncea), and salina wildrye (Leymus salinae) were among the species with a relatively high degree of resistance to the insect. Clonal lines of the Et. repens × Et. spicata hybrid differed significantly in resistance. Over 50% of the total phenotypic variation among the hybrid lines was attributed to genetic effects, indicating that selection for resistance would be effective.
    • Genetic Variability for Characters Affecting Stand Establishment in Crested Wheatgrass

      Asay, K. H.; Johnson, D. A. (Society for Range Management, 1983-11-01)
      Experiments were conducted in the laboratory (growth chamber) and field to determine the: (1) magnitude of genetic differences in crested wheatgrass [Agropyron cristatum (L.) Gaertn. and A. desertorum (Fisch. ex Link) Schult.] for characteristics related to seedling establishment on semiarid range and (2) effectiveness of laboratory procedures to estimate relative performance of breeding lines in the field. Significant differences were found among 175 crested wheatgrass progeny lines for seedling emergence, seedling height, seedling dry weight, and fall stand in the analyses of data combined over 2 field locations. The soil at both study sites was a Xerallic Calciorthids. The genetic variance among progenies comprised over 50% of the total phenotypic variance for most traits in the combined analyses of variance. Seedling emergence in the spring was positively related to fall stands (r = 0.54** to 0.61**). In growth chamber experiments involving 168 progeny lines, significant genetic variation was detected in seedling recovery after exposure to drought stress in 3 of 4 experiments. The genetic variance comprised over 50% of the total phenotypic variance in 5 of 6 instances in the combined analyses of the field data and in 3 of the 4 laboratory experiments. In general, laboratory determinations of seedling emergence under drought stress and seedling recovery after drought were not significantly related to seedling establishment in the field. A relatively close correlation between seed weight and all plant responses measured in the field (r = 0.46** to 0.57** in the pooled data) suggests that preliminary screening on the basis of seed weight appears promising.