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Title: Foliar Resistance to Ozone Injury in the Genetic Base of U.S. and Canadian Soybean and Prediction of Resistance in Descendent Cultivars Using Coefficent of Parentage

item Burkey, Kent
item Carter Jr, Thomas

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2008
Publication Date: 4/11/2009
Citation: Burkey, K.O., Carter Jr, T.E. 2009. Foliar Resistance to Ozone Injury in the Genetic Base of U.S. and Canadian Soybean and Prediction of Resistance in Descendent Cultivars Using Coefficent of Parentage. Field Crops Research. 111:207-217.

Interpretive Summary: Ground level ozone is formed by the action of sunlight on volatile hydrocarbons and nitrogen oxides produced during combustion of carbon based fuels. Although frequently considered an urban problem, ozone pollution is much broader in scope because weather systems transport the pollutants into agricultural areas. Ozone is an air pollutant that is toxic to plants, causing visible injury to foliage and a reduction in the growth and yield of sensitive crops such as soybean. Estimates suggest that current ambient ozone levels are sufficient to reduce soybean yield by 10-20% with greater yield losses anticipated if tropospheric ozone concentrations continue to rise. In the absence of successful efforts to control ozone pollution, future crop productivity may depend on the development of ozone-tolerant soybean varieties. In this study, USDA-ARS researchers conducted the first ozone screen of 30 soybean ancestors representing a majority of genes present in modern U.S. and Canadian cultivars. Using foliar injury to assess ozone response, ozone-tolerant soybean ancestors were identified for use in selection and development cultivars capable of maintaining yields under elevated ozone conditions.

Technical Abstract: Development of O3-tolerant cultivars is a potentially important approach for maintaining crop productivity under future climate scenarios where tropospheric O3 pollution is projected to rise. A first step is identification of sources of O3-tolerance genes for the major crop species. In this study, thirty ancestral lines of soybean (Glycine max (L.) Merr.), representing 92% of the pedigree in modern US cultivars, were screened for differences in ozone response. Plants were grown for 3-weeks under low O3 conditions in a greenhouse and then treated for 6-days with 77 nmol mol-1 O3 in greenhouse exposure chambers. Ozone responses were assessed by measurement of foliar injury. Foliar injury among ancestors ranged from 5 to 50 percent of leaf area on the five oldest main-stem leaves, representing substantial genetic variation in O3 sensitivity that ranged beyond control cultivars Essex and Forrest. Ancestors Fiskeby 840-7-3 and Fiskeby III exhibited the greatest O3 tolerance and PI88788 the least. A subsequent field study confirmed the O3 tolerance of Fiskeby III. Stomatal conductance differed for ancestors but was not correlated to O3 reaction, suggesting that differences in O3 sensitivity were not related to differences in O3 uptake by leaves. The tolerant ancestors identified on the basis of foliar injury represent genotypes for further testing to select germplasm that maintains seed yield under elevated O3 conditions. Based on ratings of ancestors, modern cultivars with the highest probability of O3 tolerance were identified as candidates for future study.