Submitted to: Methods in Molecular Biology
Publication Type: Book / chapter
Publication Acceptance Date: 8/4/2011
Publication Date: 6/4/2013
Citation: Jia, Y., Liu, G., Park, D., Yang, Y. 2013. Inoculation and scoring methods for rice sheath blight disease caused by Rhizoctonia solani. In: Yang, Y., editor. Rice Protocols. Methods in Molecular Biology Book Series, Volume 956. Humana Press. p. 257-268. Interpretive Summary: Sheath blight disease of rice caused by the necrotropic pathogen Rhizoctoniasolani is one of the major constraints of rice production in the Southern U.S. and worldwide. Genetic resistance has been useful in controlling the disease; however, phenotyping methods have been the bottleneck for identifying sheath blight resistance genes. In the present study, we report five improved methods under highly controlled environmental conditions for phenotyping. They are 1) detached leaf method; 2) micro-chamber method; 3) mist-chamber; 4) parafilm sachet method; and 5) aluminum foil method. These methods have been useful for screening and evaluating disease reactions of rice germplasm and facilitating the genetic mapping of disease resistance genes. It is also anticipated that they can be modified for use for other destructive plant diseases caused by necrotropic fungal pathogens.
Technical Abstract: Plant resistance (R) genes provide effective protection against invading pathogens at the front line of defense. Advances in genomic technology have accelerated efforts to characterize a wide range of crop R genes from diverse and economically important crops, resulting in effective crop protection. Thus far, over 100 plant R genes have been molecularly cloned. Most cloned plant R genes were predicted to be receptor proteins with nucleotide binding sites and a leucine rich repeat domain (NBS-LRR). In contrast, the effectors that trigger plant R gene-dependent immunity are random molecules and rapidly evolve. Understanding how plant R genes evolve to recognize the effectors is a challenge in plant biology. The map-based cloning technique is the most commonly used method for plant R gene isolation. This technique involves identification of candidate R genes based on integrated genetic and physical maps using a mapping population and verification of resistant function of R genes using genetic transformation. The techniques for map-based cloning, and structure and function of R genes with emphasis on R genes to the rice blast fungus, the most devastating fungal pathogen of rice, are reviewed.