ГЕНЕТИЧНЕ РІЗНОМАНІТТЯ КУКУРУДЗИ І СУЧАСНІ ПІДХОДИ ДО ЙОГО СИСТЕМАТИЗАЦІЇ

The article discusses the possibilities of improving the corn grading system. It has been shown that the existing classification of maize does not provide an opportunity to systematize the modern genetic diversity of this crop, which has expanded significantly in recent times due to increasing demand for specialized forms of maize. As a result, a number of objectively existing and actively practically used valuable forms do not fit within the existing classification and consequently deprived of botanical status. The expediency of using for this purpose of the phenotypic effect of mutant genes of the endosperm structure is substantiated. Since the criteria for the distribution of maize into subspecies is determined by certain features of the physical structure of the endosperm of the grain, which are due to the specificity of its biochemical composition, the effect of mutations of endosperm o2, sh1, sh2, su1, se, su2, ae and wx on the peculiarities of the phenotype, structure of the endosperm and the structure of endo-sperm maize, namely: the content and fractional composition of the protein, the content of the basic fractions of carbohydrates, the content and fatty acid composition of the oil in biologically ripe grain was analyzed. For the study, 5 lines were used based on each mutation. Significant specific effects on these indicators other than ordinary maize and the su1 and wx mutants included in the existing maize classification and having subspecies status have been identified. An additional insertion to the corn classification system of endosperm mutants o2, sh1, sh2, su2 and ae as separate subspecies is proposed, since the totality of the morphological and biochemical characteristics of the carriers of these mutations fully complies with the requirements for the classification characteristics of this culture. The official recognition of new taxonomic groups will help to objectify the generalization of modern genetic diversity of corn and will allow reliable standardized evaluation of representatives of these groups of maize, as a raw materials for use in the feed production, food, pharmaceutical and technical branches of industry. This approach is applied for the first time and has no national or foreign analogues.

Pollen tube contents initiate ovule enlargement and enhance seed coat development without fertilization

In angiosperms, pollen tubes carry two sperm cells toward the egg and central cells to complete double fertilization. In animals, not only sperm but also seminal plasma is required for proper fertilization. However, little is known regarding the function of pollen tube content (PTC), which is analogous to seminal plasma. We report that the PTC plays a vital role in the prefertilization state and causes an enlargement of ovules without fertilization. We termed this phenomenon as pollen tube–dependent ovule enlargement morphology and placed it between pollen tube guidance and double fertilization. Additionally, PTC increases endosperm nuclei without fertilization when combined with autonomous endosperm mutants. This finding could be applied in agriculture, particularly in enhancing seed formation without fertilization in important crops.

Genetic control of lysine metabolism in maize endosperm mutants

The capacity of three maize endosperm opaque mutants (o10, o11 and o13) to accumulate soluble lysine in the seed in relation to their wildtype counterpart, W22+, was investigated. The W22o13 and W22o11 mutants exhibited 278% and 186% increases in soluble lysine, respectively, while for W22o10, a 36% decrease was observed, compared with the wildtype. A quantitative and qualitative study of the N constituents of the endosperm has been conducted and data obtained for the total protein, non-protein N, soluble amino acids, albumins / globulins, zeins and glutelins present in the seed of the mutants. Following 2D–PAGE, a total of 38 different forms of zein polypeptides were detected and considerable differences were noted between the three mutant lines. The metabolism of lysine was also studied by analysis of the enzymes aspartate kinase, homoserine dehydrogenase, lysine 2-oxoglutarate reductase and saccharopine dehydrogenase, which exhibited major changes in activity, depending on the genotype, suggesting that the mutant genes may have distinct regulatory activities.

Effect of endosperm mutants on maize seed germination

The expression of genetic potential of yielding and quality of a certain genotype depends among other factors on seed quality. Seed is very important not only for the reproduction of the particular plant species, but also, for the contemporary plant production. Each part of maize seed (pericarp endosperm and germ) has a specific function in the complex process of germination and emergence. The following three genotypes of different endosperm types were observed: ZPSC 42A (standard grain quality dent hybrid) ZPSC 504 su (sweet maize hybrid with a sugary gene) and ZPSyn.II sh2 (synthetic population with a shranken2 gene). Seed viability of the stated genotypes was determined by the accepted ISTA methods: standard method accelerating age and cold test. Obtained results point out to differences in the germination capacity of the observed genotypes. The greatest reduction of the germination capacity and the emergence rate was expressed by the application of the accelerating ageing method. Appeared differences are probably a result of the endosperm texture (type), grain weight, sugar content and pericarp thickens and composition.