Large-scale identification and characterization of phenolic compounds and their marker-trait association in wheat

Phenolic compounds (PCs) are important biomolecules as they affect processing (color, aroma, and taste quality of bread, and grain hardness) and nutrition quality (antioxidant and other health benefits). This study identified a set of 115 PCs by screening 100 Indian bread wheat varieties that showed wide variation in PCs content. These PCs were classified into 29 phenolic acid and their derivative, 71 flavonoids, 2 chalcones, 8 stilbenoids 1 theaflavin, 1 eugenol, and 3 coumarins. Of the 115, standards for 25 PCs were validated by matching their RT (retention time), MS and MS/MS fragmentation pattern on UPLC-QTOF-MS/MS. The range of PC content was from 0.01 mu g/100 g for luteolin in 'GW 503' to 547.63 mu g/100 g for vanillin in 'Durgapur 65.' The marker-trait association analysis identified 81 SSR markers which were associated with twelve PCs. Of 81, 53 were significantly associated on 5% FDR at true value (p < q). After multiple test correction (adjustedpvalue and 5% FDR), eight SSR markers were significantly associated with five PCs, namely 'rutin,' 'hesperidin,' '2,4-dihydroxybenzoic acid,' 'vanillin,' and 'salicylic acid.' A substantial number of markers showed coefficient of variation (R-2) ranged from similar to 5 to 45% for these PCs. The variations present in the set of wheat varieties and linked markers can be exploited for the improvement of PCs affecting processing and nutrition quality of wheat through molecular breeding and functional genomics tools.