Interspecific crossing Zea mays L. x Mamillaria spp.--content of amino acids --Urechean, V The improvement of intergeneric and interspecific cross-breeding methods (most of the time by using the phytohormones) permitted the crossing of species more and more distant from a taxonomic point of view.

Starting from the idea that the Cactaceae family is very well adapted to dry areas, wanting to find out whether there is any gametic compatibility and hoping to obtain a transfer of genetic material to the Zea mays L. species, we realized a cross-breeding: Zea mays L. x Mamillaria spp.

As a pollen parent we used Mamillaria species (cultivated in our country only in green houses and vegetation dishes) which emits a sufficient quantity of easily collectable pollen, and the maternal parent was an inbred maize line very sensitive to drought and heat (Lc 460).

Pollination was made under a bag and a typical maize ear well covered with kernels resulted. The kernels were sowed in the field the next year and, surprisingly, the descendant F1 has the phenotypic aspect (morpho-anatomical characters) of the Zea mays L. species, presenting even the heterozygotic vigor specific for the maize hybrids cultivated in that area.

Since the two species were distant from a taxonomic point of view, the elimination of one species genome ( in this case genome of Mamillaria spp.) was expected, but the hybrid vigor put questions about the homozygotic/heterozygotic aspect of the F1 descendant.

The lack of tests for the analysis of the Mamillaria chromosomes didnít permit us to ascertain whether the whole genome of the Mamillaria species had been eliminated or a transfer of genetic material had taken place between the two species.

Our research was based on the analysis of the grainís amino acids for the maternal line Lc 460, belonging to Zea mays L. species, and also of the hybrid descendant Zea mays (Lc 460) x Mamillaria spp., comparing with the two simple maize hybrids obtained and cultivated in the same medium conditions (Table 1).

Table 1. The content of amino acid from the kernel at Zea mays L.x Mamillaria spp. in comparison with the maternal parent and two simple maize hybrids F1.
 
Amino acid Lc 460 Lc460 x M. spp. HSS409 HSS49
Aspartic acid 0.788 0.762 0.843 0.707
Threonine  0.437 0.456 0.489 0.461
Serine 0.574 0.650 0.601 0.590
Glutamic acid 1.543 1.640 1.695 1.701
Proline 0.693 0.606 0.789 0.738
Cystine 0.345 0.289 0.472 0.384
Glycine 0.401 0.491 0.429 0.390
Alanine 0868 1.054 0.826 0.750
Valine 0.625 0.503 0.550 0.522
Methionine 0.119 0.341 0.187 0.182
Isoleucine 0.479 0.403 0.676 0.559
Leucine 1.121 1.451 1.177 1.169
Tyrosine 0.836 0.652 0.657 0.750
Phenilalanine 0.809 0.847 0.777 0.851
Histidine 0.462 0.509 0.693 0.688
Lysine 0.591 0.408 0.572 0.561
Arginine 0.980 - - -
TAA% 11.671 10.062 11.407 11.003
TAAE% 5.625 4.918 5.121 4.993
TAAE/TAA% 48.17 48.87 44.89 45.40
LYS/TAA% 5.06 4.05 5.01 5.09
GLU/TAA% 13.22 16.30 14.86 15.46
ASP/TAA% 6.75 7.57 7.39 6.42
PRO/TAA% 5.93 6.02 6.91 6.70

TAA-total amino acids; TAAE-total essential amino acids; LYS- lysine; GLU- glutamic acid; ASP-aspartic acid; PRO-proline.

In the interspecific hybrid combination Zea mays L. x Mamillaria spp., the content of threonine, serine, and glutamic acid, is a little bit higher than that of the maternal inbred line (Lc 460), being close to the values of the two simple maize hybrids HSS 409 and HSS 49.

The hybrid has the highest content of glycine and a very high content of alanine in comparison to the other genotypes studied. It has, also, the highest content of methionine and leucine which is very high in comparison with the maternal form (Lc 460).

The content of tyrosine diminishes considerably in comparison with the maternal form, but stays close to the others hybrids value.

The lysine diminishes, having the lowest value related with the total of amino acids ( 4.05%).

The proline, cystine, valine, and isoleucine have also the lowest values at the hybrid combination Zea mays x Mamillaria spp. in comparison with the other genotypes studied, but the quantity of proline related to the total of amino acids (6.02%) is higher than the one obtained at the maternal form (5.93%).

Although the total content of amino acids at the hybrid combination Zea mays L. x Mamillaria spp. is lower (10.062mg/100g dray matter) there is a favorable relationship between the total content of essential amino acids and the total content of amino acids (48.87%) that is superior to the two simple maize hybrids (HSS 409 and HSS 49).

The glutamic and aspartic acid, as precursors of the other amino acids , also have the highest values.

All these differences between the hybrid combination Zea mays L. x Mamillaria spp. and the maternal form (the inbred maize line Lc 460) led us to believe that between the two parent plants belonging to two distant species, from a taxonomic point of view, but also geographically isolated, a transfer of genetic material took place.

Subsequent studies, especially an analysis of the chromosomal maps, will be able to show exactly whether these kinds of crossings are recommended for the improvement of maize programs or not.
 
 


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