Explicando a origem e a evolução da fragrância no arroz

The origin and evolution of fragrance in rice (Oryza sativa L.)

Michael J. Kovacha, Mariafe N. Calingacionb, Melissa A. Fitzgeraldb and Susan R. McCoucha,1

+ Author Affiliations

aCornell University, Department of Plant Breeding and Genetics, Ithaca, NY 14853; and

bGrain Quality Nutrition and Postharvest Centre, International Rice Research Institute, Los Baños, Philippines

Abstract

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

Footnotes

1To whom correspondence should be addressed. E-mail: srm4@cornell.edu

Author contributions: M.J.K., M.A.F., and S.R.M. designed research; M.J.K. and M.N.C. performed research; M.J.K., M.A.F., and S.R.M. analyzed data; and M.J.K., M.A.F., and S.R.M. wrote the paper.

Edited by Brian A. Larkins, University of Arizona, Tuscon, AZ, and approved July 10, 2009

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

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