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Relationships Between Disease Reactions under Controlled Conditions and Severity of Wheat Bacterial Streak in the Field. E. A. Milus, Assistant Professor, Department of Plant Pathology, University of Arkansas, Fayetteville 72701. E. Duveiller, Plant Pathologist, Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Lisboa 27, Apdo Postal 6-641, Col. Juarez, Del. Cuauhtemoc, 06600 Mexico D.F., Mexico; T. L. Kirkpatrick, Associate Professor, Southwest Research and Extension Center, 362 Hwy 174 North, Hope, AR 71801; and D. B. Chalkley, Research Specialist, Department of Plant Pathology, University of Arkansas, Fayetteville 72701. Plant Dis. 80:726-730. Accepted for publication 9 March 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0726.

Bacterial streak of wheat is best controlled by resistant cultivars, but there are difficulties associated with screening for resistance under field conditions. Screening for resistance under controlled conditions could facilitate the development of resistant cultivars if there is a good relationship between disease reaction and disease severity. The objective of this study was to determine the relationships between bacterial streak reactions on primary leaves of seedlings or flag leaves of adult plants and bacterial streak severity on adult plants in the field. Fifty spring wheats and 24 winter wheats were evaluated. Except for spring wheat cultivar reactions on primary leaves, reactions (ranks) of greenhouse-grown cultivars were significantly and positively related (r ranged from 0.60 to 0.64 with P ≤ 0.0012) to ranks of cultivars evaluated for bacterial streak severity. However, selection for low percentages of water-soaking under controlled conditions would keep a few wheats that were susceptible in the field and discard several wheats that were resistant in the field. Because of these discrepancies we cannot recommend inoculation under controlled conditions as a reliable means of screening a random sample of wheats for bacterial streak resistance.

Keyword(s): Xanlhomonas campestris pv. translucent, Xanthomonas campestris pv.undulosa