Rice Resistance to Planthoppers and Leafhoppers

Abstract

For over 50 years, host-plant resistance has been regarded as an efficient method to reduce yield losses to rice caused by delphacid and cicadelid hoppers. Already a number of resistant rice varieties have been developed and deployed throughout Asia. To date, over 70 hopper resistance genes have been identified in rice; however, less than 10 genes have been deliberately introduced to commercial rice varieties. Currently, due to recent brown planthopper (Nilaparvata lugens [Stål]) and whitebacked planthopper (Sogatella furcifera [Horvath]) outbreaks occurring at an unprecedented scale, researchers are working toward a second generation of resistant varieties using newly identified gene loci and applying new molecular breeding methods. This paper reviews advances in the identification of resistance genes and QTLs against hoppers in rice. It collates all published information on resistance loci and QTLs against the major rice planthoppers and leafhoppers and presents information on gene locations, genetic markers, differential varieties, and wild rice species as sources of resistance. The review indicates that, whereas progress in the identification of genes has been rapid, considerable tidying of the information is required, especially regarding gene nomenclature and resistance spectra. Furthermore, sound information on gene functioning is almost completely lacking. However, hopper responses to resistance mechanisms are likely to be similar because a single phenotyping technique has been applied by most national and international breeding programs during germplasm screening. The review classifies genes occurring at two chromosome regions associated with several identified resistance loci and highlights these (Chr4S: BphR-R and Chr12L: BphR-R) as general stress response regions. The review calls for a greater diversity of phenotyping methods to enhance the durability of resistant varieties developed using marker-aided selection and emphasizes a need to anticipate the development of virulent hopper populations in response to the field deployment of genes.

Keywords:

• adaptation
• brown planthopper
• genetic analysis
• green leafhopper
• green rice leafhopper
• host plant resistance
• molecular markers
• Nephotettix cincticeps Uhler
• Nephotettix virescens (Distant)
• Nilaparvata lugens (Stål)
• Sogatella furcifera (Horvath)
• whitebacked planthopper

ACKNOWLEDGMENTS

The authors thank Jedeliza Ferrater and Holden Verdeprado for help in compiling data sources. We thank Adithi Vardarajan and Sumanth Mutte for assistance in classifying genes into COG protein categories. DF was funded by Pioneer (SKEP Program) during 2010 and through the Ministry of Agriculture, Forestry and Fisheries of Japan (Japan-CGIAR Fellowship Program in 2011-2012. This is paper #1 from the New Paradigms in Ricehopper Resistance Workshop held at IRRI, Los Baños, Philippines in October 2010. Funding for the workshop was provided by the Japanese Ministry of Agriculture and the Research Directorate of IRRI. We thank JS Bentur (Directorate of Rice Research, India) and Peter de Jong (Wageningen University, The Netherlands) for kindly reviewing the manuscript and for many helpful suggestions to improve the text.