Genetic variability of the phloem sap metabolite content of maize ([i]Zea mays[/i] L.) during the kernel-filling period
Résumé
Using a metabolomic approach, we have quantified the metabolite composition of the phloem sap exudateof seventeen European and American lines of maize that had been previously classified into five maingroups on the basis of molecular marker polymorphisms. In addition to sucrose, glutamate and aspartate,which are abundant in the phloem sap of many plant species, large quantities of aconitate and alaninewere also found in the phloem sap exudates of maize. Genetic variability of the phloem sap compositionwas observed in the different maize lines, although there was no obvious relationship between the phloemsap composition and the five previously classified groups. However, following hierarchical clusteringanalysis there was a clear relationship between two of the subclusters of lines defined on the basis ofthe composition of the phloem sap exudate and the earliness of silking date. A comparison betweenthe metabolite contents of the ear leaves and the phloem sap exudates of each genotype, revealed thatthe relative content of most of the carbon- and nitrogen-containing metabolites was similar. Correlationstudies performed between the metabolite content of the phloem sap exudates and yield-related traitsalso revealed that for some carbohydrates such as arabitol and sucrose there was a negative or positivecorrelation with kernel yield and kernel weight respectively. A posititive correlation was also foundbetween kernel number and soluble histidine.