BACKGROUND: Studies were carried out on the creation of haploinductor lines using various methods for testing haploinductor and marker ability from the VIR maize genetic collection, adapted to the conditions of the Liaoning province in China and the South of Russia. MATERIALS AND METHODS: On 22 maize testers, studies were carried out on the creation of haploinductor lines and testing the haploinductor and marker ability by the test-cross method. Sources of R1-nj, B1, Pl1 genes from the VIR maize genetic collection were used. RESULTS: The lines of maize haploinducers Liaoyu No. 1, Liaoyu No. 2, Liaoyu No. 3 and Liaoyu No. 4 were created with a haploinduction frequency of 6.85%, 7.53%, 6.66% and 6.03%. respectively, with a high quality of labeling with the R1-nj, B1, Pl1 genes in test crosses. CONCLUSIONS: In the process of selection of haploid maize on the basis of genes A, haploinductor lines with a high frequency of haploinduction and high efficiency of markers in test crosses, abundant pollen and grain productivity, resistance to late blight and lodging, and adaptation to the agroclimatic zone of Shenyang Province (China) were obtained and the North Caucasian Federal District (Russia).
The discovery of spontaneous haploid plants and the development of ways to produce them in in vitro culture have set a new direction important for breeding and for theoretical research in reproductive biology. The frequency of spontaneous haploidy in cultivated plants is extremely low and does not exceed 0.01-0.1%, therefore, the search for sources and donors capable of stimulating haploidy in hybrid combinations is of current interest. Expansion of the search for new sources and donors of the haploinduction trait, the creation of new, more effective haploinducers contribute to the accumulation of scientific information and genetic sources, characterized by a high resource potential for selection and genetic research. The causеs of haploidy are not well understood yet. According to the available information, the genes localized in the qhir1, qhir11, qhir12 regions of chromosome 1 in maize are responsible for this process. The use of genes that stimulate haploinduction in maize in combination with the marker gene R1-nj responsible for anthocyanin coloration of the caryopsis and embryo, as well as genes A1 and B1, which are in control of the entire plant coloration, allowed the creation of haploinducer lines with a frequency of haploid stimulation up to 15%. Phenotypic expression of dominant alleles of the marker anthocyanin coloration genes in different parts of a hybrid plant, as well as in the caryopsis and embryo, contributes to the high-quality selection of haploid kernels in the cob due to the manifestation of recessive alleles of these genes at the haploid level. The presence of anthocyanin synthesis suppressor genes in siliceous maize (C1-I, C2-Idf, In1-D) restricts the use of the R1-nj gene in other representatives of siliceous maize. In order to overcome this problem, studies are underway to create other genotypes of haploinducers, which are not associated with the anthocyanin coloration of the caryopsis, but instead have other marker traits, such as the oil content in the kernel, the absence of ligules in the leaves, and root coloration in seedlings. The use of matroclinous and androclinous types of haploinduction allows breeders to obtain highly homozygous dihaploid maize lines, with both the maternal and paternal genomes. These achievements made it possible to cut five or more times the material and time inputs into the creation of inbred lines and their sterile analogs, accelerate the breeding of new maize hybrids, and signifi cantly improve the quality of seed production in terms of typicality and uniformity. The materials presented in the article should help breeders and geneticists to learn more about the innovative directions and problems of hybrid maize breeding.
Abstract. Hybrid maize breeding requires constant renewal of the source material. In this regard, broadening of genetic variation in parental lines is one of the primary tasks in heterotic hybrid breeding programs. The use of reverse diploid inbred lines derived from a tetraploid population is considered as an innovative approach to achieve this goal.Results. The investigated material comprised 106 reverse diploid (rediploid) inbred lines originating from diploid plants selected in segregating selfed progenies of triploid populations and consequently subjected to inbreeding, while triploid populations resulted from a cross between plants of a tetraploid population with a broad genetic basis and a diploid line. The use of a system of crosses with 37 sterile testers belonging to different FAO maize maturity groups allowed the evaluation of the rediploid lines’ combining ability and the response to M and C types of CMS. Field tests were conducted in 2019 in the steppe zone of Kabardino-Balkaria. Forty-six lines (43.3%) with the combining ability ranging from ultra-high to good, and 78 lines (73.6%) maintaining the CMS character were identified. Among them, 59 lines (55.7%) were maintainers for the M type CMS, 15 lines (14.1%) for C type CMS, and 4 lines maintained sterility for both CMS types. Sixteen lines (15.1%) restored pollen fertility of the forms with M type CMS, 11 lines (10.4%) were restorers for the C-type and one line turned out to be a universal restorer for both CMS types. Ranking by the “sprout - flowering of ears” interstage period duration showed that most of the lines (66.0%) with the ability to maintain sterility or restore male fertility of M and C CMS types, as well as with the combining ability from ultrahigh to good (32.6%) fell into the group with the flowering period duration of 51-55 days. According to the results of the harvested grain moisture assessment, the hybrids ♀(РГС246с × OL213) × ♂92с5986·2·3, ♀714М × ♂1/67-1 and ♀714М × ♂92н136-4, with the values of 13, 6%, 13.9%, 14.0%, respectively, were identified. The hybrids ♀714М × ♂1/67- 1 and ♀(OL563С × KL1392) × ♂92с0653 2 1 2 were characterized by the maximum value of the selection index, i.e. 5.03 and 5.13, respectively.Conclusions. The results of the studies showed the breeding value of rediploid lines as an initial material for hybrid maize breeding.
A collection of tetraploid sweet corn has been created on the basis of Baksanskaya Sugary var. (VIR catalog no. k-23426) obtained from dent corn tetraploid population MRPP-20 characterized with high grain yield of its ear. The variety has been created by inbreeding separate caryopses homozigotic for su1 and su2 genes (sugary endosperm); the caryopses were selected from MRPP-20 population with subsequent selection work for valuable traits during a number of generations. The collection includes over 300 specimens, among them there are genotypes promising for selection of foodcrop sweet corn. The research was conducted into principal phenotypic traits of the plant and chemical components of its caryopsis (protein, starch, oil). Analysis has shown that the chemical composition of grain varies widely. Structural phenotypic traits of vegetative organs differ mainly in the number of ears per plant, ear size, number of seeds per ear and the number of seed rows, caryopsis length, color of corncob and the caryopsis itself. Specimens with high (17.0–18.0 %) and low (11.0–12.0 %) protein content, high (9.0–10.0 %) and low (5.0–6.0 %) oil content, high (66.0–67.0 %) and low (60.0–61.0 %) starch content in caryopses were produced. Specimens have been obtained that combine high starch content with low oil content (C-1042) and vice versa (C-1114, C-1116), with low protein and oil content in a combination with high starch content (C-1180, C-1370). The research results allowed choosing starting material for selection work with hybrids of sweet corn to get predefined flavor properties.
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