Genetic purity testing of maize hybrids using a MALDI-TOF mass spectrometric method

Wednesday, May 18, 2016

Authors: Zsanett Simon, Csaba Lovász

 

1. Summary
Mass spectrometry is one of the most versatile techniques of modern instrumental methodologies. Starting from the most sensitive analytical instruments, through application in space research, to the intelligent scalpel (iknife), there is almost no scientific area where the advantages of the method cannot be exploited. In this paper the application of mass spectrometry in a new area is presented.
From an economic point of view, maize is one of our most important crops 5 to 8 million tons of which is produced annually in Hungary. For this industrial scale production, high quality seeds are essential, and this requires a systematic, strict control of the seeds. In this spirit, identification and elimination of seeds of dubious origin or of poor quality are important tasks of growers and seed producers. Genetic purity of seeds the varietal identity is one of the most important qualification parameters.

Our research goal was to develop a state-of-the-art, effective analytical method to test the genetic purity and varietal identity of maize seeds, and to prove the applicability of our method by measurements.

The procedure is based on the application of MALDI-TOF-MS (Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry), with the help of which the unique masses of the proteins of maize grains can be investigated. Following the extraction of maize grains, proteins characteristic of the given parents can be selected from among the different mass number peaks (proteins) appearing in the mass spectra of the extracts, which can then be followed as genetic markers during the testing of hybrid seeds. To check the MALDI-TOF-MS method, our analytical results were compared to results obtained by the recommended reference method (isoelectric focusing – IEF). Results of the tests performed so far are promising, there is a very good agreement with the results obtained by the reference method. Exact results were also provided by our method when testing fungus-infected maize seed batches, while such lots can only be analyzed by the reference method in a limited way. Running on the gel using isoelectric focusing is affected by fungal infection, which makes the evaluation of the results harder, in some cases even impossible.
Our MALDI-TOF mass spectrometric method developed for the genetic purity testing of maize seeds proved to be satisfactory not only because of its speed, sensitivity and comparable results, but it also made the analysis of fungus-infected hybrids possible.

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