Potassium fertilization reduces the severity of leaf spot complex and mosaic in Megathyrsus maximus cultivars.
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ABSTRACT - The objective of this study was to evaluate the effects of potassium (K) on disease severity and the chemical composition of Megathyrsus maximus cultivars. The experiment was conducted in a randomized block design in a 6 × 4 factorial arrangement, consisting of six Megathyrsus maximus cultivars (Massai, Mombaça, Tamani, Tanzânia, Quênia, and Zuri) and four K doses (0, 205, 410, and 820 mg dm−3 ). The severity of the leaf spot complex, caused by Bipolaris maydis and B. yamadae, was assessed using a diagrammatic scale. A significant interaction between K doses and cultivars was observed for all evaluated diseases. At K doses of 0 and 205 mg dm−3 , the Tanzânia cultivar showed lower leaf spot severity compared with the other cultivars, whereas at higher doses, no disease symptoms were observed in any cultivar. The area under the disease progress curve (AUDPC) for mosaic followed a linear model only for the Tanzânia cultivar, whereas quadratic regression models best described the response for the remaining cultivars, with maximum mosaic severity values of 67.74% for Quênia, 72.34% for Mombaça, 76.99% for Zuri, 74.88% for Massai, and 68.93% for Tamani. Increasing K doses reduced the severity of both the leaf spot complex and mosaic. However, the leaf spot complex did not affect the nutritional value of the evaluated cultivars.
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Mancha Foliar, Panicum Maximum, Potássio, Leaf spot, Megathyrsus maximus, Potassium, Tanzania