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Stalk Rot Resistance and Strength of Maize Stalks from the Plant Introduction Collection. R. L. Clark, USDA-ARS, Departments of Agronomy, Plant Pathology, and Seed and Weed Sciences, Iowa State University, Ames 50011. D. C. Foley, Department of Plant Pathology, Seed, and Weed Sciences, Iowa State University, Ames 50011. Plant Dis. 69:419-422. Accepted for publication 18 October 1984. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1985. DOI: 10.1094/PD-69-419.

A sample of accessions from the Plant Introduction (PI) collection of maize germ plasm contained accessions more resistant to stalk rot than the check hybrid AES704. Stalk rot severity was measured by the extent of discoloration in the internodes and reduction in maximum rind strength. Differences in stalk rot ratings were mostly at the 8-wk rating, but some accessions had less than the maximum amount of rot at 10 wk. PI accessions with reduced stalk rot at 10 wk postinoculation included 221835, 270080, 270290, 279022, 357099, 357100, 357103, 357107, and 357116. In 1975, PI 269751, with a rot rating of 6 at 10 wk, also tested high in maximum fiber stress (MFS). The accession with the highest average MFS in all tests was PI 393711, with an MFS of 322 MPa, or 31% better than the check hybrid AES704. The PI accession with the highest mean MFS in relation to the check hybrid was 195757, with an MFS of 271 MPa, or 71% better than the check. The mean breaking force (K) of stalk rinds was negatively correlated with rot rating means of the accessions in all years. Either K or MFS could be used to measure stalk rot severity.

Keyword(s): corn, Diplodia maydis, Zea mays.