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Title: Bridging conventional and molecular genetics of sorghum insect resistance

Author
item Huang, Yinghua
item SHARMA, HARI - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item DHILLON, MUKESH - Indian Agricultural Research Institute

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 10/1/2012
Publication Date: 1/3/2013
Citation: Huang, Y., Sharma, H.C., Dhillon, M.K. 2013. Bridging conventional and molecular genetics of sorghum insect resistance. In: Paterson, A.H., editor. Genomics of the Saccharinae, Chapter 16. Plant Genetics and Genomics: Crops and Models, Vol. 11. Springer, New York. p. 367-389.

Interpretive Summary: Sorghum is grown in warm and humid environments that often favor the proliferation of many insect pests. In addition, long growth periods of some varieties such as sweet sorghum and forage sorghum, cultivation of genetically homogeneous hybrids/varieties on large acreages, and the practice of multi-cropping sorghum and rotation by intercropping with common host plants throughout the year results in the buildup of pest populations. Thus, insect pest populations often exceed the economic-injury level in most of the sorghum growing areas. In the past decades, genetic improvement of sorghum focused on identification of natural pest resistance and breeding of pest-resistant cultivars and hybrids to defend against insect pests. Successful deployment of resistant crops contributed an important component of the integrated pest management. Recent advances in sorghum genetics, genomics and breeding have led to development of cutting-edge molecular technologies that are complementary to genetic improvement of this crop for insect pest management. Genome sequencing and molecular markers have accelerated the pace of gene discovery in sorghum. Other genomic technologies, such as QTL (quantitative trait loci) mapping, gene expression profiling, functional genomics, and gene transfer are powerful tools for efficient identification of novel insect resistance genes, and characterization of the key pathways that regulate the interactions between crop plants and insect pests leading to successful expression of the host plant defense. All above-mentioned molecular and genomic approaches promise to facilitate efficient development of insect-resistant cultivars and hybrids of sorghum. Future research efforts that combine the power of molecular genetics with the knowledge and experience accrued by classical plant breeding will provide portable and inexpensive DNA markers that can be used by plant breeders to select and develop the next generation of multi-purpose sorghum crops.

Technical Abstract: Sustainable production of sorghum, Sorghum bicolor (L.) Moench, depends on effective control of insect pests as they continue to compete with humans for the sorghum crop. Insect pests are major constraint in sorghum production, and nearly 150 insect species are serious pests of this crop worldwide, and cause more than 9% loss annually. Annual losses due to insect pests in sorghum have been estimated to be $1,089 million in the semi-arid tropics (ICRISAT 1992), but differing in magnitude on a regional basis. Key insect pests in the U.S. include the greenbug, Schizaphis graminum (Rondani); sorghum midge, Stenodiplosis sorghicola (Coquillett); and various caterpillars in the Southern areas. For example, damage by greenbug to sorghum is estimated to cost U.S. producers $248 million annually. The major insect pests of sorghum on a global basis are the greenbug, sorghum midge, sorghum shoot fly (Atherigona soccata Rond.), stem borers (Chilo partellus Swin.and Busseola fusca Fuller), and armyworms (Mythimna separata Walk and Spodoptera frugiperda J.E. Smith). Recent advances in sorghum genetics, genomics and breeding have led to development of some cutting-edge molecular technologies that are complementary to genetic improvement of this crop for insect pest management. Genome sequencing and genome mapping have accelerated the pace of gene discovery in sorghum. Other genomic technologies, such as QTL (quantitative trait loci) mapping, gene expression profiling, functional genomics, and gene transfer are powerful tools for efficient identification of novel insect resistance genes, and characterization of the key pathways that regulate the interactions between crop plants and insect pests leading to successful expression of the host plant defense. Traditional breeding methods, such as germplasm evaluation and enhancement, backcrossing, pedigree selection, and recurrent selection continue to play important roles in developing insect-resistant cultivars with major resistance genes; and new cultivars with enhanced resistance to several important insect pests are released continuously. Future research efforts should focus on identification of new sources of resistance, characterization of resistance genes, and dissecting the network of resistance gene regulation. Collaboration between research institutions and the sorghum industry as well as international cooperation in utilization of emerging knowledge and technologies will enhance the global efforts in insect pest management in sorghum.