Control of Black Chaff of Wheat with Seed Treatment and a Foundation Seed Health Program

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Abstract
The eradication of Xanthomonas campestris pv. translucens from wheat seeds (Triticum aestivum) together with a foundation seed health program was evaluated for control of black chaff of wheat. The following chemical treatments were evaluated for eradicating X. c. pv. translucens: methoxyethylmercury acetate, ethylmercury-toluene sulphonanilide, phenylmercury acetate, cupric hydroxide, calcium hypochlorite, sodium hypochlorite, calcium propionate, and acidified cupric acetate (ACA). Naturally contaminated seeds were treated and assayed for X. c. pv. translucens by 1) plating seeds and seed washing onto XTS semi-selective agar and 2) sowing treated and untreated seeds in fields plots in Kimberly, ID [USA]. The pathogen was detected by laboratory assays of seed from all treatments, except those treated with ACA. Similar results were obtained in fields tests. The ACA treatment adversely affected germination and stand, but was the only one that controlled black chaff. To produce X. c. pv. translucens-free seed for the foundation seed health program, seed of three naturally contaminated seedlots was treated with ACA, assayed, and sown for increase. This procedure (using untreated seed) was repeated the 2 subsequent years. No diseases was observed in the 3 years of the study. Xanathomonas campestris pv. translucens was not detected in seed assays following the ACA treatment or in first and third generation seed. However, a trace level of the pathogen was detected in the second generation seed. A foundation seed health programs can be an effective control for black chaff in the absence of other sources of inoculum.