AROMA IN RICE - GENETIC-ANALYSIS OF A QUANTITATIVE TRAIT

A new approach was developed which succeeded in tagging for the first time a major gene and two QTLs controlling grain aroma in rice. It inv olved a combination of two techniques, quantification of volatile comp ounds in the cooking water by gas chromatography, and molecular marker mapping. Four types of molecular marker were used (RFLPs, RAPDs, STSs , isozymes). Evaluation and mapping were performed on a doubled haploi d line population which (1) conferred a precise character evaluation b y enabling the analysis of large quantities of grains per genotype and (2) made possible the comparison of gas chromatography results and se nsitive tests. The population size (135 lines) provided a good mapping precision. Several markers on chromosome 8 were found to be closely l inked to a major gene controlling the presence of 2-acetyl-1-pyrroline (AcPy), the main compound of rice aroma. Moreover, our results showed that AcPy concentration in plants is regulated by at least two chromo somal regions. Estimations of recombination fractions on chromosome 8 were corrected for strong segregation distortion. This study confirms that AcPy is the major component of aroma. Use of the markers linked t o AcPy major gene and QTLs for marker-assisted selection by successive back-crosses may be envisaged.