Rice Resistance to Brown Spot Mediated by Nitrogen and Potassium |
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Authors: | Maristela Pereira Carvalho Fabricio Avila Rodrigues Patricia Ricardino Silveira Camila Cristina Lage Andrade Julio Cezar Parpaiola Baroni Henrique Sá Paye José Eustáquio Loureiro Junior |
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Institution: | Authors’ address: Department of Plant Pathology, Laboratory of Host‐Parasite Interaction, Vi?osa Federal University, Vi?osa, 36570‐000, Minas Gerais State, Brazil (correspondence to F. A. Rodrigues. E‐mail: fabricio@ufv.br) |
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Abstract: | This study was undertaken to investigate the effects of both nitrogen (N) and potassium (K) rates on rice resistance to brown spot, caused by the fungus Bipolaris oryzae. Rice plants (cultivar ‘Metica 1’) were grown in soil corrected with 0, 25, 50, 75 and 100 mg of N / kg (as NH4NO3) of soil as well as with 25, 50, 75, 125 and 150 mg of K / kg (as KCl) of soil. Thirty‐three‐day‐old plants were inoculated with a suspension of Bipolaris oryzae conidia and the incubation period (IP), number of lesions (NL) per cm2 of leaf area and disease severity was evaluated. Disease severity was scored at 24, 48, 72, 96, 120 and 144 h after inoculation and data were used to obtain the area under brown spot progress curve (AUBSPC). Soil plant analysis development (SPAD) index, plant dry weight and concentration of N and K in leaf tissues were also determined for both non‐inoculated (NI) and inoculated (IN) plants. Concentration of N in leaf tissue increased as the N rates in the soil increased. Concentration of K in leaf tissue increased sharply as the K rates in the soil increased for both NI and IN plants. Concentration of K in leaf tissue was not affected by N rates. The IP increased as the N rates increased, but was somewhat less impacted by increasing K rates. The NL decreased as the N rates increased. The NL dramatically declined at the highest K rates. The AUBSPC dramatically declined as the N and K rates in the soil increased. SPAD index values increased as the N and K rates in the soil increased for both NI and IN plants. Plant dry weight increased as the N and K rates in the soil increased for both NI and IN plants. Results from this study suggest that combining high N and K rates may contribute to reducing the intensity of brown spot in rice while improving plant development. |
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Keywords: | Bipolaris oryzae foliar disease Oryza sativa plant nutrition SPAD index |
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