Identification of causal agent and management of grain discolouration in rice

  • Rajendra PersaudEmail author
  • Mahendra Persaud
  • Duraisamy Saravanakumar
  • Oudho Homenauth
Original Article


Grain discolouration has been noticed in rice over the years in Guyana. The disease has been a serious problem in affecting quality and yield of rice. A study was carried out to identify the causal agent of grain discolouration and to develop suitable disease management practices in rice. The initial identification revealed that Curvularia spp. was predominant in rice grains with expression of symptoms of grain discolouration from samples collected from various locations of Guyana. The Centre for Agriculture and Biosciences International (CABI) of the UK has confirmed the pathogen as Curvularia lunata, based on the amplification and sequence analysis of internal transcribed spacer (ITS) region of the rDNA. Pathogenicity test has proved that C. lunata is responsible for the cause of grain discolouration. Eight new-generation fungicides were tested against C. lunata under in vitro and field conditions. All fungicides recorded a significant inhibition of mycelial growth of the C. lunata under in vitro. Fungicides that exhibited higher than 70% inhibition of mycelial growth of C. lunata compared to the untreated control were further evaluated in multiple field trials. Application of Amistar Xtra 28 SC (Triazol, Estrobilurtina, Cyproconazol, Azoxystrobin) 1.5 mL L−1; Glory 75 WG (Mancozeb + Azoxystrobin) at 3.0 g L−1; Antracol 70WP (Propineb) at 5.0 g L−1; and Carbendazim 50SC (Carbendazim 50%) at 1.5 mL L−1 showed more than 50% reduction in the incidence of grain discolouration. The efficacy of Amistar Xtra 28 SC; Glory 75 WG; Antracol 70WP; and Carbendazim 50SC were further demonstrated in field trials established with three replicates and an individual plot size of 225 m2 at farmers’ holdings in regions 2, 3, 4, 5 and 6 of Guyana. A significant reduction in grain discolouration was noticed from 48.58 to 92.85% in field demonstrations. In addition, these four fungicides have enhanced number of filled grains, 1000 grain weight and grain yield compared to control.


Rice Grain discolouration Curvularia lunata Management Fungicides 



The first author is thankful to Guyana Rice Development Board (GRDB) for providing him with the necessary funding and laboratory facility to conduct this research work at the GRDB, Rice Research Station, Burma and within the rice industry in Guyana.

Author’s contributions

First author Rajendra Persaud has designed, carried out the experiments, analyzed the data and written the manuscript. Other authors have provided technical advice, guidance and assistance to carry out the work and edit the manuscript.

Compliance with ethical standards

Conflict of interest

There is no potential conflict of interest to declare.


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Copyright information

© Deutsche Phytomedizinische Gesellschaft 2019

Authors and Affiliations

  1. 1.Department of Plant Pathology and Plant BreedingGuyana Rice Development Board (GRDB)MahaiconyGuyana
  2. 2.Department of Food Production, Faculty of Food and AgricultureThe University of the West IndiesSt. AugustineTrinidad and Tobago
  3. 3.National Agricultural Research and Extension Institute (NAREI)Mon ReposGuyana

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