Abstract
When a phenotype of interest is associated with an external/internal covariate, covariate inclusion in quantitative trait loci (QTL) analyses can diminish residual variation and subsequently enhance the ability of QTL detection. In the in vitro synthesis of 2-acetyl-1-pyrroline (2AP), the main fragrance compound in rice, the thermal processing during the Maillard-type reaction between proline and carbohydrate reduction produces a roasted, popcorn-like aroma. Hence, for the first time, we included the proline amino acid, an important precursor of 2AP, as a covariate in our QTL mapping analyses to precisely explore the genetic factors affecting natural variation for rice scent. Consequently, two QTLs were traced on chromosomes 4 and 8. They explained from 20% to 49% of the total aroma phenotypic variance. Additionally, by saturating the interval harboring the major QTL using gene-based primers, a putative allele of fgr (major genetic determinant of fragrance) was mapped in the QTL on the 8th chromosome in the interval RM223-SCU015RM (1.63 cM). These loci supported previous studies of different accessions. Such QTLs can be widely used by breeders in crop improvement programs and for further fine mapping. Moreover, no previous studies and findings were found on simultaneous assessment of the relationship among 2AP, proline and fragrance QTLs. Therefore, our findings can help further our understanding of the metabolomic and genetic basis of 2AP biosynthesis in aromatic rice.
Highlights
Scent is considered one of the most important traits of rice grain quality because a strong and pleasant fragrance plays a considerable role in rice marketing [1]
In order to effectively exploit aromatic rice, a comprehensive consideration of molecular and evolutionary aspects in terms of both genomic and metabolic factors that might affect this valuable trait should be taken into account
Various studies have shown the proline is a vital precursor for 2AP biosynthesis [44, 45, 46, 47, 48]
Summary
Scent is considered one of the most important traits of rice grain quality because a strong and pleasant fragrance plays a considerable role in rice marketing [1]. An Efficient Solution to Enhance QTL Detection Ability volatile flavor compounds associated with aromatic rice, 2-acetyl-1-pyrroline (2AP) has been found to be the primary cause of the distinctive aroma in Basmati and Jasmine rice [2]. The key intermediate in the formation of rice flavor, 2AP, is 1-pyrroline formed from proline by Strecker degradation. According to radio-labeling research, the nitrogen contained in the pyrroline ring of proline becomes the nitrogen contained in the pyrroline ring of 2AP in aromatic rice [3].
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