Rice Genetics IV - IRRI books - International Rice Research Institute

The functions of these sequences need further study. We also mapped 12 of theseclones to their respective chromosomal locations and the correspondence between themap locations and the single-locus QTLs and epistatic loci remains to be established.PerspectivesThe tools of genetic mapping and functional genomics that are available today havemade it possible to precisely characterize the mechanism of heterosis. As demonstratedin our studies, genetic mapping using molecular markers can determine thegenomic locations of loci (single-locus QTLs and also epistatic interactions) that controlthe performance and heterosis of the traits. Such analyses can also provide informationregarding the magnitudes of the effects of the QTLs and epistatic loci on thetrait. Gene expression analysis, using techniques such as differential display, subtractivecDNA cloning, or cDNA microarray, can lead to the identification of genes thatare differentially expressed between the parents and the hybrid, or between highlyheterotic hybrids and nonheterotic hybrids. There is also a considerable need for physiologicaland biochemical characterization of the nature of the genes involved in heterosisas well as the processes underlying heterosis. We believe that comprehensiveanalysis combining the differentially expressed genes, genetically determined QTLsand epistatic loci, and physiologically characterized biochemical processes will eventuallylead to complete elucidation of the biology of heterosis.ReferencesAllard RW. 1956. Formulas and tables to facilitate the calculation of recombination values inheredity. Hilgardia 24:235-278.Causse MA, Fulton TM, Cho YG, Ahn SN, Chunwongse J, Wu KS, Xiao JH, Yu ZH, RonaldPC, Harrington SE, Second G, McCouch SR, Tanksley SD. 1994. Saturated molecular mapof the rice genome based on an interspecific backcross population. Genetics 138:1251-1274.Davenport CB. 1908. Degeneration, albinism and inbreeding. Science 28:454-455.East EM. 1908. Inbreeding in corn. Reports of the Connecticut Experiment Station for years1907-1908. p 419-428.Kurata N, Nagamura Y, Yamamoto K, Harushima Y, Sue N, Wu J, Antonio BA, Shomura A,Shimizu T, Lin SY, Inoue T, Fukuda A, Shimano T, Kuboki Y, Toyama T, Miyamoto Y,Kirihara T, Hayasaka K, Miyao A, Monna L, Zhong HS, Tamura Y, Wang ZX, Momma T,Umehara Y, Yano M, Sasaki T, Minobe Y. 1994. A 300-kilobase interval genetic map ofrice including 883 expressed sequences. Nat. Genet. 8:365-372.Liang P, Pardee AB. 1992. Differential display of eukaryotic messenger RNA by means of thepolymerase chain reaction. Science 257:967-971.Lincoln S, Daly M, Lander E. 1992a. Mapping genes controlling quantitative traits withMAPMAKER/QTL 1.1. Whitehead Institute Technical Report, 2nd ed. Cambridge, Mass.,USA.Lincoln S, Daly M, Lander E. 1992b. Constructing genetic maps with Mapmaker/Exp 3.0.Whitehead Institute Technical Report, Cambridge, Mass., USA.184 Qifa Zhang et al