Fluorescence test for selection of high-tryptophan genotypes of maize
--Fedenko, VS; Struzhko, VS; Tikhomirov, AYe

A distinctive feature of maize is that seeds are not balanced in protein composition and vital amino acids, such as tryptophan and lysine. To create maize with improved protein quality (QPM) a genetic method based on the endosperm opaque-2 mutation is usually used. The problem of estimating the quality of the selection material is characterised by these methods. Presence of the o2 gene is shown in the lowering of the portion of zein that does not have tryptophan, and increase of the relative portion of the tryptophan carrying fraction of protein. Thus, the index of tryptophan contained in grains may be used as an integral feature of protein balance improvement.

Accordingly, we seek an express-method for selection of high-tryptophan maize genotypes based on fluorescence parameters of cut or milled grains. The suggested diagnostic criterion is based on optical features of QPM forms. It has long-wave displacement of ultraviolet fluorescence compared with ordinary analogs. As an object for investigation, lines based on o2 mutation and o2 double recessive have been used with forms that have endosperm modified type and high-lysine hybrids. It has been found that a fluorescence maximum of grain cut for ordinary hybrids is in the interval 312.7-313.3 nm; for high-lysine analogs this maximum is in the 327.7-329.0 nm range. As compared with other diagnostic tests that are well-known, it is possible to analyze an individual kernel without any biochemical reagents. One of the main important notes is that a grain is vital after analysis. This fluorescence test can carry out individual screening of high tryptophan grains and include them in another cycle of selection programmes. 

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