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A leaf spot complex of WB881' durum (Triticum turgidum L. var. durum), similar to symptoms observed in winter wheat (Triticum aestivum L), was greatly suppressed by Cl at a field site in Montana. The objectives were to determine: (i) if this leaf spot phenomenon could be reproduced under hydroponics; (ii) the effect of Cl on leaf spot severity, water use, and plant growth; (iii) whether Br could substitute for Cl; and (iv) whether other durum cultivars were susceptible to leaf spotting under Cl deficiency, WB881 durum was grown at four halide (Cl and Br) levels of 1.5, 3.0, 6.0, and 30.0 mmole pot -1 , plus a control. Three cultivars (WB881, Kyle, and Monroe) were grown at Cl levels of 0, 1.2, and 24.0 mmole pot -1 . Withholding Cl from starter and refill solutions reproduced leaf spotting in WB881 similar to symptoms observed in the field. Leaf spotting was suppressed by Cl up to the 30.0 mmole pot -1 dose, but was aggravated by Br. Plant water use increased with Cl up to the 30.0 mmole pot -1 dose and was related to the beneficial effect of Cl in suppressing tissue necrosis. Leaf spot severity was closely related to shoot Cl concentration, tissue necrosis was minor if Cl concentration was ≥1.0 g kg -1 , but increased exponentially below this level. Withholding Cl from the hydroponic cultures reduced shoot and grain yield 58.2 and 98.9%, respectively, bromide did not substitute for Cl by improving shoot and grain yield. Monroe was less susceptible to this Cl-deficient leaf spot than was WB881 or Kyle. Cultivar susceptibility or tolerance to leaf spotting could not be explained by differences in Cl partitioning within the plant (e.g., roots, shoots, leaves). |
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