Host induced gene silencing of Rhizoctonia solani MAP kinase genes, RPMK1 and RPMK2, an efficient strategy to produce sheath blight resistant rice

AJ Manoharan1, IM Tiwari2, TR Sharma1 and JR Botella2

  1. Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia
  2. National Research Centre on Plant Biotechnology, Pusa Campus, New Delhi-110012,INDIA

R. solani is an economically important plant pathogen. It has a world wide distribution and is estimated to infect nearly all cultivable plants. Sheath blight disease of rice caused by R. solani is especially devastating, causing as much as 50% yield losses annually. Despite this threat effective strategies to control this pathogen are still lacking. In recent times, genetically modifying plants to produce RNAi triggers to silence pathogen genes, also known as Host Delivered RNAi, has emerged as a promising technology to produce pathogen resistant plants. In this work, we developed the HDRNAi technology to produce sheath blight resistant rice. Susceptible rice cultivar, Taipei-309 was transformed to encode inverted repeats that target both R. solani MAP kinase genes – RPMK1 and RPMK2. These genes are homologues of Magnaporthe grisea pathogenicity MAP Kinase (PMK1).pmk1 mutants show complete loss of pathogenicity phenotype. In our study, transgenic rice lines when assayed for R. solani disease resistance, they show delayed disease development, reduced lesion number and lesion size as compared to wild type control. Additionally, R. solani infecting the transformed rice lines displayed reduced mRNA levels for both the RPMK genes – an average of 57% and 66% reduction respectively for RPMK1 and RPMK2. This is the first report demonstrating utility of HDRNAi to produce sheath blight resistant rice. Keywords: HD-RNAi, Rhizoctonia solani, Sheath blight, Disease Resistance, Taipei-309, MAP Kinase.