Brown Spot of Rice is Affected by Photon Irradiance and Temperature

• Published in: Journal of phytopathology Vol. 159; no. 9; pp. 630 - 634
• Main Authors: Dallagnol, Leandro José, Rodrigues, Fabrício Ávila, DaMatta, Fábio Murilo
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-09-2011; Blackwell
• Subjects: Biological and medical sciences; Bipolaris oryzae; Brown spot; Canopies; Fructose; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Glucose; Greenhouses; Irradiance; Leaves; light intensity; Oryza sativa; Photons; photosynthesis; Phytopathology. Animal pests. Plant and forest protection; Plant diseases; Relative humidity; soluble sugars; Sucrose; Sugar; Temperature effects; Monocotyledones; Temperature; Plant pathogen; soluble sugars; Cereal crop; Bipolaris oryzae; Fungi; Oryza sativa; light intensity; Gramineae; Angiospermae; Spermatophyta; Fungi Imperfecti; Photosynthesis
• ISSN: 0931-1785; 1439-0434
• DOI: 10.1111/j.1439-0434.2011.01819.x

Brown spot, caused by Bipolaris oryzae, is one of the most destructive diseases in rice. In this study, the effect of photon irradiance and temperature on brown spot development was evaluated. The concentration of total soluble sugars (fructose, glucose and sucrose) in rice leaves was also evaluated. Rice plants of cv. ‘Oochikara’ were inoculated with B. oryzae and kept in a greenhouse [20 ± 2°C (night time) and 35 ± 2°C (day time), ≈ 1000 μmol photons/m2/s] or two different mist chambers (25 or 32 ± 2°C, ≈ 15 μmol photons/m2/s at the top canopy). Plants kept in a mist chamber at 32 ± 2°C, under low photon irradiance, showed reduced incubation period (IP) and increase in the rate of lesion expansion. Brown spot severity in rice leaves was 67.8% at 32 ± 2°C, 27.8% at 25 ± 2°C and 11.4% under greenhouse conditions. The highest brown spot severity was found on plants grown under low photon irradiance, in which soluble sugar concentrations were lowest, suggesting that disease development was boosted under these particular growing conditions. Based on the results of this study, a continuous high temperature and low photon irradiance, in the presence of high relative humidity, and low soluble sugars contribute to an increase in brown spot development.