Construction of LC-MS maps of root exudates in cotton (Gossypium hirsutum L.) seedlings

Root exudates composition and pattern of biochemical expression is genotype specific and highly influenced by both by abiotic and biotic factors. During this investigation, various attempts made to standardize the techniques to construct LC-MS maps using cotton as a plant system. Construction of root exudates maps by LC-MS analysis found as very unique and having high utility in genotype identification through genotypic maps, detecting the presence/absence of specific chemicals of interest, and for rhizosphere engineering. As expected each sample (root exudates of a particular genotype) produced very distinct peaks-spectra. Each peak in the peak-spectral map (Y-axis) provides very useful information, the peak intensity (peak height), which represents the percent of each chemical/analyte present in the sample. The total number of peaks in each spectrum indicates the number of biochemicals present in that sample. The root exudates samples were probed in both positive and negative LC-MS mode, since some acidic compounds could not be detected in positive mode. The peaks displayed in the negative mode spectra maps indicates most of them are belong to the compounds in acidic groups. This distinction also provides additional chemical diversity and chemical specificity to include in the genotypic maps. By this way, the diversity present in all these parameters for each cotton genotype was included and the information presented was used to establish a very high-resolution maps. These peak spectral maps directly depend on the biochemicals produced by a specific genotype and genetically controlled; therefore, they can be called as genotypic maps or root exudates maps. Keywords: Root Exudates, Silica sand, Liquid Chromatography mass spectroscopy (LC-MS)