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Fragrance in the grain is one of the most highly valued grain quality traits in rice, yet the origin and evolution of the betaine aldehyde dehydrogenase gene (BADH2) underlying this trait remains unclear. In this study, we identify eight putatively nonfunctional alleles of the BADH2 gene and show that these alleles have distinct geographic and genetic origins. Despite multiple origins of the fragrance trait, a single allele, badh2.1, is the predominant allele in virtually all fragrant rice varieties today, including the widely recognized Basmati and Jasmine types. Haplotype analysis allowed us to establish a single origin of the badh2.1 allele within the Japonica varietal group and demonstrate the introgression of this allele from Japonica to Indica. Basmati-like accessions were nearly identical to the ancestral Japonica haplotype across a 5.3-Mb region flanking BADH2 regardless of their fragrance phenotype, demonstrating a close evolutionary relationship between Basmati varieties and the Japonica gene pool. These results clarify the relationships among fragrant rice varieties and challenge the traditional assumption that the fragrance trait arose in the Indica varietal group.BADH2 ͉ Basmati ͉ Jasmine R ecent findings suggest that although Asian cultivated rice (Oryza sativa) is comprised of several genetically distinct groups, a number of the alleles responsible for key domestication and grain quality traits are shared among these groups. Given the complex evolutionary history of rice, the origin of these genetic alterations and how they came to exist across the highly divergent subpopulations of O. sativa remain central questions in rice evolutionary biology.

BackgroundThe domestication of Asian rice (Oryza sativa) was a complex process punctuated by episodes of introgressive hybridization among and between subpopulations. Deep genetic divergence between the two main varietal groups (Indica and Japonica) suggests domestication from at least two distinct wild populations. However, genetic uniformity surrounding key domestication genes across divergent subpopulations suggests cultural exchange of genetic material among ancient farmers.Methodology/Principal FindingsIn this study, we utilize a novel 1,536 SNP panel genotyped across 395 diverse accessions of O. sativa to study genome-wide patterns of polymorphism, to characterize population structure, and to infer the introgression history of domesticated Asian rice. Our population structure analyses support the existence of five major subpopulations (indica, aus, tropical japonica, temperate japonica and GroupV) consistent with previous analyses. Our introgression analysis shows that most accessions exhibit some degree of admixture, with many individuals within a population sharing the same introgressed segment due to artificial selection. Admixture mapping and association analysis of amylose content and grain length illustrate the potential for dissecting the genetic basis of complex traits in domesticated plant populations.Conclusions/SignificanceGenes in these regions control a myriad of traits including plant stature, blast resistance, and amylose content. These analyses highlight the power of population genomics in agricultural systems to identify functionally important regions of the genome and to decipher the role of human-directed breeding in refashioning the genomes of a domesticated species.

No abstract

The interaction of an alkyl polyglycidol surfactant with hydrogen‐passivated silicon from dilute hydrofluoric acid solutions has been measured using wettability and attenuated total reflection Fourier transform infrared spectroscopic techniques. The surfactant was found to be very effective in rendering hydrophobic hydrogen‐terminated silicon hydrophilic in the hydrofluoric acid solutions. The adsorption of the surfactant, and its desorption when rinsed with deionized water, were very rapid. However, approximately 20 % of the adsorbed surfactant remained on the silicon surface even after prolonged rinsing. © 1999 The Electrochemical Society. All rights reserved.