With the aim of studying the mobilization of storage proteins during seed germination, we have evaluated free amino acid content in hybrids between a maize inbred line (OU) and Balsas teosinte (Zea mays ssp. parviglumis var. parviglumis) (Zmpp). F1 hybrid seeds resulting from the OU x Zmpp cross and their respective parent seeds were arranged to germinate in Petri dishes at a constant temperature of 28 C and darkness. Ten mature grains, previously sterilized, were placed into each dish. Each 24 hours, and during six hours running, samples of 10 grains each were taken from each dish (2 repetitions) for each representative of this experiment.

The different samples were dried in the oven at a temperature of 65 C until they reached a constant weight, and then protein and water-soluble free amino acid (FAA) content was evaluated, expressing them in equivalent leucine micro mols (µm Leu) per 100mg of seeds. On the basis of seed dry weight and protein content, FAA was expressed per seed and per 100mg of protein (see Table 1). In mature grains which were not placed in Petri dishes to germinate, we have taken the measurements for the zero day (day 0), to be able to calculate the mean free amino acid liberation rate (MFAALR), which was expressed in leucine micromols/100mg of protein per day. The experimental results obtained are shown in Table 1 and we give a graphical representation of the free amino acid content variation and their liberation rate in Figures 1 and 2.

The mature grains of the hybrids and their respective parents do not significantly differ in their initial free amino acid and protein contents. The liberation of free amino acids during the germination process does not show any significant difference until 4 days after the initial incubation. From the fifth day, hybrids show a free amino acid content which is significantly greater than that of their parents. At the end of the experiment, free amino acid content was increased 10 or 15 times if we compared to the initial one. These produce a greater liberation of free amino acids in hybrids, as a direct consequence of a higher liberation rate (see Figure 2).

After 6 days incubation, hybrids have almost a 50% higher free amino acid content than their parents. The results obtained point out a greater proteolytic activity in hybrids, probably associated with a greater seed vigour, expressed through faster growing and mobilization of grain storage.

The results obtained through this simple experiment document once more the possibilities offered by maize wild relatives to increase the biological efficiency of the cultivated species (maize).

Table 1. Free amino acid content (FAA) during germination in OU maize inbred Balsas teosinte (Zmpp) and its hybrids derived from OU x Zmpp cross.

Figure 1. Variation of free amino acid content (FAA) expressed in µMLeu/100 mg protein, during germination of maize inbred (OU), Balsas teosinte (Zmpp) and OU x Zmpp hybrid seeds.

Figure 2. Variation of mean free amino acid liberation rate (MFAALR) expressed in µMLeu/100 mg protein day, during germination of maize inbred (OU), Balsas teosinte (Zmpp) and OU x Zmpp hybrid seeds.

Ida G. Palacios and Jorge L. Magoja

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