QTL distribution of the 12 C and N metabolites and the first two principal components derived from the whole field. Chla, Chlorophyll a; Chlb, chlorophyll b; Mala, malate; Fuma, fumarate; Glut, Glu; AA, total amino acids; Prot, protein; Nitr, nitrate; Prin1, first principal component; Star, starch; Sucr, Suc; Gluc, Glc; Fruc, Fru; Prin2, second principal component.