Incomplete Dominance Research Articles

Improving the green mass quality with the help of heterosis breeding

The most reliable and effective way to improve both productivity and quality of green mass is the use of heterosis breeding. The purpose of the current work was to study the heterosis effect of green mass quality indicators in sorghum-Sudan hybrids developed based on cytoplasmic male sterility. The object of the study was the sorghum-Sudan hybrids developed by the Agricultural Research Center “Donskoy”. Dry matter productivity varied among the hybrids within 746-1202 g/m2 . The highest values have been observed in the combinations with the CMS-line ‘APV-1115’ (1045 g/m2 ). The heterosis effect on the dry matter productivity was found in all hybrids. Four hybrids ‘APV-1115 x Kudesnitsa’, ‘APV-1115 x ChT-22’, ‘Dzhetta x ChT-2’, ‘APV-1115 x Svetloplenchataya 4’ have significantly exceeded the standard in terms of dry matter productivity by 184-270 g/m2 with high rates of hypothetical (38.1-64.1%), true (93.2-142.0%) and competitive (19.8-28.9%) heterosis. Digestible protein yield has ranged from 49 to 84 g/m2 . Among the hybrids, the greatest heterosis effect was identified in the hybrids ‘Demetra x Svetloplenchataya 4’ (Hhyp.=43.4%, Htrue.=125.4%), ‘Dzhetta x Yaktik’ (Hhyp.=70.5%, Htrue.=142.3%), ‘APV-1115 x Kudestitsa’ (Hhyp.=72.8%, Htrue.=108.9%), ‘APV-1115 x Svetloplenchataya 2’ (Hhyp.=81.0%, Htrue.=118.4%), ‘APV1115 x ChT-22’ (Hhyp.=103.3%, Htrue.=118.4%). In the course of the study, there has been found that according to the content of crude protein, ash, oil, fiber and nitrogen-free extractive substances (NES), the most hybrids possessed partial or incomplete dominance of large values. However, to obtain even a slight heterosis according to the content of protein, fiber, and NES content, at least one parent had to have high trait values. Based on the complex of the heterotic effect according to the green mass quality indicators, there have been identified such hybrids as ‘Dzhetta x Yaktik’, which exceeded the large parental form in terms of dry matter (Htrue.=10.5%) and oil (Htrue.=14.4%); ‘Dzhetta x ChSS’ which exceeded the large parental form in terms of dry matter and crude protein (Htrue.=14.3 and 1.3%); ‘Demetra x Svetloplenchataya 4’ which exceeded the large parental form in terms of crude protein, dry matter, and ash (Htrue.=3.8; 5.9 and 6.4%, respectively). In general, the data obtained have indicated the prospects of using cytoplasmic male sterility in breeding not only for productivity, but also for quality.

A novel strategy to map a locus associated with flowering time in canola (Brassica napus L.).

Flowering time is an important agronomic trait for canola breeders, as it provides growers with options for minimizing exposure to heat stress during flowering and to more effectively utilize soil moisture. Plants have evolved various systems to control seasonal rhythms in reproductive phenology including an internal circadian clock that responds to environmental signals. In this study, we used canola cultivar 'Westar' as a recurrent parent and canola cultivar 'Surpass 400' as the donor parent to generate a chromosome segment substitution line (CSSL) and to map a flowering time locus on chromosome A10 using molecular marker-assisted selection. This CSSL contains an introgressed 4.6 mega-bases (Mb) segment (between 13 and 17.6Mb) of Surpass 400, which substantially delayed flowering compared with Westar. To map flowering time gene(s) within this locus, eight introgression lines (ILs) were developed carrying a series of different lengths of introgressed chromosome A10 segments using five co-dominant polymorphic markers located at 13.5, 14.0, 14.5, 15.0, 15.5, and 16.0Mb. Eight ILs were crossed with Westar reciprocally and flowering time of resultant 16 F1 hybrids and parents were evaluated in a greenhouse (2021 and 2022). Four ILs (IL005, IL017, IL035, and IL013) showed delayed flowering compared to Westar (P < 0.0001), and their reciprocal crosses displayed a phenotype intermediate in flowering time of both homozygote parents. These results indicated that flowering time is partial or incomplete dominance, and the flowering time locus mapped within a 1Mb region between two co-dominant polymorphic markers at 14.5-15.5Mb on chromosome A10. The flowering time locus was delineated to be between 14.60 and 15.5Mb based on genotypic data at the crossover site, and candidate genes within this region are associated with flowering time in canola and/or Arabidopsis. The co-dominant markers identified on chromosome A10 should be useful for marker assisted selection in breeding programs but will need to be validated to other breeding populations or germplasm accessions of canola.

Unraveling the Genetic Mechanisms of Maize Ear Diameter Heterosis

Hybridization has long been a crucial strategy for breeders aiming to develop high-yield crops vital for global food security. However, the exact molecular mechanisms driving heterosis (hybrid vigor) remain a topic of debate. Maize (Zea mays), which demonstrates pronounced heterosis, serves as an ideal model for studying this phenomenon. In our study, we carefully measured phenotypic changes in ear diameter, tracing its development from the inflorescence meristem (IM) to the floral meristem (FM) stages. Our findings revealed a complex progression: the hybrid's ear diameter followed an additive pattern during the IM and spikelet pair meristem (SPM) stages, shifted to incomplete dominance at the spikelet meristem (SM) stage, and ultimately displayed over-dominance at the FM stage. Notably, significant phenotypic changes occurred during the SM stage with gene expression primarily showing non-additive patterns. Gene Ontology (GO) enrichment analysis highlighted the role of cell redox homeostasis genes, which exhibited over-dominant expression in hybrids, as key contributors to heterosis. Furthermore, we identified a distinct gene expression category - dominant maternal or paternal gene expression in F1 hybrids (DMP) - characterized by exclusive expression in the hybrid and one parent, while remaining inactive in the other. This category of DMP genes plays a pivotal role in shaping the diverse gene expression patterns observed in hybrids, distinguishing them from their parental lines. In conclusion, the widespread occurrence of non-additive expression seems to enhance the efficiency of biological processes and energy distribution in hybrids, ultimately driving the manifestation of heterosis.

No evidence of altered language laterality in people who stutter across different brain imaging studies of speech and language.

A long-standing neurobiological explanation of stuttering is the incomplete cerebral dominance theory, which refers to competition between two hemispheres for 'dominance' over handedness and speech, causing altered language lateralization. Renewed interest in these ideas came from brain imaging findings in people who stutter of increased activity in the right hemisphere during speech production or of shifts in activity from right to left when fluency increased. Here, we revisited this theory using functional MRI data from children and adults who stutter, and typically fluent speakers (119 participants in total) during four different speech and language tasks: overt sentence reading, overt picture description, covert sentence reading and covert auditory naming. Laterality indices were calculated for the frontal and temporal lobes using the laterality index toolbox running in Statistical Parametric Mapping. We also repeated the analyses with more specific language regions, namely the pars opercularis (Brodmann area 44) and pars triangularis (Brodmann area 45). Laterality indices in people who stutter and typically fluent speakers did not differ, and Bayesian analyses provided moderate to anecdotal levels of support for the null hypothesis (i.e. no differences in laterality in people who stutter compared with typically fluent speakers). The proportions of the people who stutter and typically fluent speakers who were left lateralized or had atypical rightward or bilateral lateralization did not differ. We found no support for the theory that language laterality is reduced or differs in people who stutter compared with typically fluent speakers.

Morphology and Inheritance of Wavy Flower Form in Periwinkle (Catharanthus roseus (L.) G. Don).

Periwinkle (Catharanthus roseus (L.) G. Don) is renowned for its diverse colors and resilience to harsh climates. Still, most commercial cultivars predominantly display flat petals. Using cultivars representing non-wavy, medium-wavy, and extreme-wavy flower forms, we examined morphological differences in both their mature leaves and floral organs. Phenotypes of self-pollinated (S1) and cross-pollinated (F1, F2) populations further underscored their morphological distinctions. Specifically, the extreme-wavy type displayed elliptical leaves, broader than the non-wavy type, with a pronounced acute apex and a notably wrinkled blade surface. The non-wavy type also bore intensely wavy petal margins and exhibited a smaller flower diameter, with a notable absence of a functional pistil, indicating female sterility. The insights gained allowed for early differentiation during the seedling period. This study suggests that the inheritance of these flower forms is regulated by an allele WAVY (Wv), which exhibits incomplete dominance. Concretely, the non-wavy form arises from a recessive homozygous expression (wvwv), the extreme-wavy from a dominant homozygous expression (WvWv), and the medium-wavy from a heterozygous expression (Wvwv). This study provides clarity on morphological descriptions and inheritance patterns of wavy flower forms, facilitating strategic breeding of diverse flower forms in periwinkle.

The course of tuberculosis infection in hyper-susceptible mice carrying the &lt;i&gt;H2&lt;/i&gt;ᵛ haplotype

Genetic regulation of the host susceptibility to Mycobacterium tuberculosis (Mtb) and severity of tuberculosis (TB) infection remain incompletely investigated. Identification of particular genes and involved in TB control and immune reactions regulated by these genes is essential for our understanding of pathogenesis of the disease, discovery of drug targets and rational vaccine development. We have shown that mice of the B10.SM (H2ᵛ) strain are extremely TB susceptible; meanwhile, the general genome structure of this mouse strain and the H2ᵛ haplotype itself are poorly characterized. We selected a pool of Mit genetic markers differentiating B10.SM mice from Chr. 17-congenic mice of the B10 strain by the PCR products motility in the electrophoresis setting. TB susceptibility of B10 mice is much lower than that of B10.SM. In the model of infection triggered by two different dosed of Mtb (100 and 600 CFU per mouse) administered via respiratory tract we demonstrated that B10.SM mice have significantly shorter survival time and significantly higher lung mycobacterial multiplication compared to B10 mice. We demonstrated (intracellular staining and ELISA) that IFNγ production in the lungs of infected mice of the two strains corresponds well to their disease phenotypes. Thus, more resistant B10 mice possess significantly more lung IFNγ-positive CD4⁺ T cells and a higher level of IFNγ secretion. We have established (B10х B10.SM) F1 hybrids and demonstrated that the post-infection phenotypes of survival time, lung mycobacterial multiplication and IFNγ production in these mice are intermediate compared to parental mice. Thus, we deal with the genetic trait with incomplete dominance expression. These data were confirmed in F2 hybrids by segregation genetic analysis. To characterize the phenotype of B10.SM mice in more detail, we vaccinated these mice with the BCG vaccine before TB challenge. Vaccination significantly prolonged survival time, diminished mycobacterial multiplication in the lungs and the degree of lung tissue pathology. Thus, a high level of susceptibility to primary infection did not interfere with BCG vaccination efficacy. We intend to continue genetic and immunologic analyses of TB-hyper-susceptible B10.SM mice. Experimental data regarding the cause of extreme disturbances in protection against infection are prerequisite for our better understanding causality of the wide spectrum of TB manifestations in human populations, as well as for rational search for novel vaccines and medications against TB infection.

Sources and donors of the multi-row ear trait for hybrid breeding of corn in the VIR collection

BACKGROUND: The sign of the number of rows of grains on the cob is one of the key to improving the productivity of corn. The effects of the genes that control this trait have been poorly studied. The search for sources and donors of this trait is relevant for hybrid breeding. AIM: The aim of this study is to search for sources and donors of the multi-row ear trait in the VIR collection for involvement in the breeding of hybrid corn. MATERIALS AND METHODS: The studies were carried out on 16 lines (S3–6) with different inbredness and varying the number of rows of grains on an ear from 18 to 36, the exotic 8-row race CUZCO characterized by large grains and the MP-20 population with 20–36 rows of ears. Hybridization and crop recording were carried out in the field conditions of the foothill zone of the Kabardino-Balkarian Republic. RESULTS: Based on similar phenotypic characteristics, 16 lines of corn with a multi-row cob were ranked into 5 groups. Analysis of the structure of the ear of the experimental F1 hybrid between the MP-20 population and the 8-row, large-grain race CUZCO showed that the trait of multi-row ear and large-grain is manifested as incomplete dominance. The yield potential of the experimental simple hybrid was no less than 12.2 tons per 1 hectare with a harvest grain moisture content of 37% and an FAO ripeness group of at least 600. A significant drawback of corn lines with multi-row cobs is the high harvest moisture content of the grain. CONCLUSIONS: The collection of multirow maize lines serves as a valuable source of genes that control important quantitative traits and can be involved in the breeding of hybrid maize for its improvement.

High-density linkage to physical mapping in a unique Tall × Dwarf coconut (Cocos nucifera L.) outbred F2 uncovers a major QTL for flowering time colocalized with the FLOWERING LOCUS T (FT).

The coconut tree crop (Cocos nucifera L.) provides vital resources for millions of people worldwide. Coconut germplasm is largely classified into 'Tall' (Typica) and 'Dwarf' (Nana) types. While Tall coconuts are outcrossing, stress tolerant, and late flowering, Dwarf coconuts are inbred and flower early with a high rate of bunch emission. Precocity determines the earlier production of a plantation and facilitates management and harvest. A unique outbred F2 population was used, generated by intercrossing F1 hybrids between Brazilian Green Dwarf from Jiqui (BGDJ) and West African Tall (WAT) cultivars. Single-nucleotide polymorphism (SNP) markers fixed for alternative alleles in the two varieties, segregating in an F2 configuration, were used to build a high-density linkage map with ~3,000 SNPs, anchored to the existing chromosome-level genome assemblies, and a quantitative trait locus (QTL) mapping analysis was carried out. The linkage map established the chromosome numbering correspondence between the two reference genome versions and the relationship between recombination rate, physical distance, and gene density in the coconut genomes. Leveraging the strong segregation for precocity inherited from the Dwarf cultivar in the F2, a major effect QTL with incomplete dominance was mapped for flowering time. FLOWERING LOCUS T (FT) gene homologs of coconut previously described as putatively involved in flowering time by alternative splice variant analysis were colocalized within a ~200-kb window of the major effect QTL [logarithm of the odds (LOD) = 11.86]. Our work provides strong phenotype-based evidence for the role of the FT locus as the putative underlying functional variant for the flowering time difference between Dwarf and Tall coconuts. Major effect QTLs were also detected for developmental traits of the palm, plausibly suggesting pleiotropism of the FT locus for other precocity traits. Haplotypes of the two SNPs flanking the flowering time QTL inherited from the Dwarf parent BGDJ caused a reduction in the time to flower of approximately 400 days. These SNPs could be used for high-throughput marker-assisted selection of early-flowering and higher-productivity recombinant lines, providing innovative genetic material to the coconut industry.

Confirmation and inheritance of glufosinate resistance in an Amaranthus palmeri population from North Carolina.

A putative glufosinate-resistant Amaranthus palmeri population was reported in 2015 in Anson County, North Carolina. The results from dose-response assays conducted in the field suggested plants were surviving lethal rates of glufosinate. Dose-response assays conducted in the glasshouse determined the Anson County accession exhibited reduced susceptibility to glufosinate compared to three glufosinate-susceptible populations. The LD50 values (210-316 g ai ha-1) for the Anson County population were always higher than the LD50 values (118-158 g ai ha-1) for the tested susceptible populations from the dose-response assays. Anson County plants that survived lethal glufosinate rates were reciprocally crossed with susceptible plants to create F1 genotypes and treated with a lethal rate of glufosinate (267 g ai ha-1; ascertained from glasshouse dose-response assay) to determine the distribution of injury and survival for each cross compared to a cross of susceptible parents. The distribution of injury was non-normal for the crosses containing an Anson County plant compared to the cross with a susceptible parent. Survival was 68%-84% for crosses containing an Anson County plant, whereas the survival was significantly reduced to 35% for the susceptible plant cross. Chi-square goodness of fit tests were used to test inheritance models to describe the responses of the genotypes. The resistant × susceptible crosses were best described with a heterozygous two loci with incomplete dominance model compared to the resistant × resistant cross that was best described with a heterozygous single locus with incomplete dominance model. The Anson County population has evolved resistance to glufosinate that is heritable and likely conferred by an oligogenic mechanism with incomplete dominance.

Clarifying Mendelian vs non-Mendelian inheritance.

Gregor Mendel developed the principles of segregation and independent assortment in the mid-1800s based on his detailed analysis of several traits in pea plants. Those principles, now called Mendel's laws, in fact, explain the behavior of genes and alleles during meiosis and are now understood to underlie "Mendelian inheritance" of a wide range of traits and diseases across organisms. When asked to give examples of inheritance that do NOT follow Mendel's laws, in other words, examples of non-Mendelian inheritance, students sometimes list incomplete dominance, codominance, multiple alleles, sex-linked traits, and multigene traits and cite as their sources the Khan Academy, Wikipedia, and other online sites. Against this background, the goals of this Perspective are to (1) explain to students, healthcare workers, and other stakeholders why the examples above, in fact, display Mendelian inheritance, as they obey Mendel's laws of segregation and independent assortment, even though they do not produce classic Mendelian phenotypic ratios and (2) urge individuals with an intimate knowledge of genetic principles to monitor the accuracy of learning resources and work with us and those resources to correct information that is misleading.

The G932C mutation of chitin synthase 1 gene (CHS1) mediates buprofezin resistance as confirmed by CRISPR/Cas9-mediated knock-in approach in the brown planthopper, Nilaparvata lugens

The brown planthopper (Nilaparvata lugens) is a major destructive rice pest in Asia. High levels of insecticide resistance have been frequently reported, and the G932C mutation in the chitin synthase 1 (CHS1) gene has been found to mediate buprofezin resistance. However, there has been no direct evidence to confirm the functional significance of the single G932C substitution mutation leading to buprofezin resistance in N. lugens. Here, we successfully constructed a knock-in homozygous strain (Nl-G932C) of N. lugens using CRISPR/Cas9 coupled with homology-directed repair (HDR). Compared with the background strain susceptible to buprofezin (Nl-SS), the knock-in strain (Nl-G932C) showed a 94.9-fold resistance to buprofezin. Furthermore, resistant strains (Nl-932C) isolated from the field exhibited a 2078.8-fold resistance to buprofezin, indicating that there are other mechanisms contributing to buprofezin resistance in the field. Inheritance analysis showed that the resistance trait is incomplete dominance. In addition, the Nl-G932C strain had a relative fitness of 0.33 with a substantially decreased survival rate, emergence rate, and fecundity. This study provided in vivo functional evidence for the causality of G932C substitution mutation of CHS1 with buprofezin resistance and valuable information for facilitating the development of resistance management strategies in N. lugens. This is the first example of using CRISPR/Cas9 gene-editing technology in a hemipteran insect to directly confirm the role of a candidate target site mutation in insecticide resistance.

A higher-yield hybrid rice is achieved by assimilating a dominant heterotic gene in inbred parental lines.

The exploitation of heterosis to integrate parental advantages is one of the fastest and most efficient ways of rice breeding. The genomic architecture of heterosis suggests that the grain yield is strongly correlated with the accumulation of numerous rare superior alleles with positive dominance. However, the improvements in yield of hybrid rice have shown a slowdown or even plateaued due to the limited availability of complementary superior alleles. In this study, we achieved a considerable increase in grain yield of restorer lines by inducing an alternative splicing event in a heterosis gene OsMADS1 through CRISPR-Cas9, which accounted for approximately 34.1%-47.5% of yield advantage over their corresponding inbred rice cultivars. To achieve a higher yield in hybrid rice, we crossed the gene-edited restorer parents harbouring OsMADS1GW3p6 with the sterile lines to develop new rice hybrids. In two-line hybrid rice Guang-liang-you 676 (GLY676), the yield of modified hybrids carrying the homozygous heterosis gene OsMADS1GW3p6 significantly exceeded that of the original hybrids with heterozygous OsMADS1. Similarly, the gene-modified F1 hybrids with heterozygous OsMADS1GW3p6 increased grain yield by over 3.4% compared to the three-line hybrid rice Quan-you-si-miao (QYSM) with the homozygous genotype of OsMADS1. Our study highlighted the great potential in increasing the grain yield of hybrid rice by pyramiding a single heterosis gene via CRISPR-Cas9. Furthermore, these results demonstrated that the incomplete dominance of heterosis genes played a major role in yield-related heterosis and provided a promising strategy for breeding higher-yielding rice varieties above what is currently achievable.

A diallel study to detect genetic background variation for FHB resistance in winter wheat

Breeding for resistance to Fusarium head blight (FHB) relies strongly on a limited number of larger-effect resistance QTL that have been mapped and associated with nearby markers. Smaller-effect (background) resistance QTL may also contribute moderate levels of resistance yet are mostly poorly characterized. Overall resistance of a genotype is determined by the combined action of both types of resistance QTL. This study aimed to identify well-adapted, advanced hard red winter (HRW) wheat breeding lines with useful background resistance QTL. A diallel trial consisting of 11 parents and 55 non-reciprocal F1 hybrids was tested for Type II FHB resistance in a replicated greenhouse experiment. Significant differences were detected among entries for disease severity (DS), general combining ability (GCA) and specific combining ability (SCA) with four parents being identified as the best general combiners with lowest DS. The ratio of GCA:SCA effects suggested that additive QTL effects were of primary importance. Overall, resistance QTL showed incomplete dominance, an excess of dominant alleles, and a greater contribution of positive effect genes. F2 of the six best F1 hybrids with the lowest DS were compared in a second greenhouse FHB trial to select possible transgressive segregates for continued evaluation and line development.

Generation mean analysis to study the genetics of fruit yield and yield attributing traits in bitter gourd

Bitter gourd (Momordica charantia L.), is a prized cucurbitaceous vegetable of the tropics, having high present-day demand along with higher future potential. Keeping the need for high yielding genotype, the present study was performed using the observations from six generations [Parent-1 (CBM-12), Parent-2 (Pusa Purvi), F1, F2, Back Cross 1 (BC1) and Back Cross 2 (BC2)]. The Generation mean analysis revealed that F1 showed intermediate performance of Parent 1 and Parent 2, while few traits showed incomplete dominance. There was lower occurrence of inbreeding depression. Using the scaling and joint scaling test, it was revealed that for fruit length, the additive [d] (6.08) effect was significant and higher than the dominance [h] effect. A significant additive [d] effect was also observed for the fruit shape index (1.75) and fruit weight (45.45). The magnitude of the dominance × dominance [I] effect was higher than the other two epistasis interactions (i.e. additive × additive [i] and additive × dominance [j]) in the majority (nine out of thirteen) of the traits. It was evident that yield is a complex and polygenic trait governed by many genes in a cumulative manner showing both additive (predominant) and non-additive gene interaction. The existence of epistasis with duplicate type predominant, as compared to complementary, in genetic control of all the traits studied, was also revealed.

Melanophilin Polymorphism in Ferrets of Different Color.

In mammals, the main contribution to the variability of pigmentation is made by two groups of genes directly related to the metabolic pathways of pigment synthesis and controlling the transport of melanosomes in melanocytes to keratinocytes. In order to identify the genetic basis of pigmentation variants, the nucleotide sequences of the melanophilin gene were compared in two groups of ferrets-silver-colored and wild-type animals-using sequencing of 16 exons. In carriers of silver color, a single nucleotide deletion was detected in the 9th exon, leading to a shift in the reading frame and the formation of a stop codon downstream. The protein encoded by the mutant allele is almost completely devoid of the C terminal domain of the protein responsible for the contact of melanosomes with actin during their moving to the periphery of melanocytes, but it retains the leading domain involved in the formation of melanosomes. The combination of the preservation of the N domain and the defect of the C domain of the mutant protein for the first time makes it possible to explain the incomplete dominance of the wild-type protein in heterozygotes.

Rating System for Phytophthora Root Rot Influences Quantitative Trait Locus Detection and Reveals Incomplete Dominance and Duplicative Recessive Epistatic Gene Action in Capsicum annuum.

Phytophthora capsici is one of the most devastating pathogens facing pepper (Capsicum annuum) producers worldwide. Numerous factors, such as the race of the pathogen, the growing environment, and the source of resistance, have resulted in an overall lack of widely applicable molecular markers associated with resistance. Our objective was to determine the effect of the rating system on quantitative trait locus (QTL) detection and understand inheritance patterns of host resistance that can influence selection and molecular marker accuracy. We evaluated an F2:11 recombinant inbred line population screened against the highly virulent strain (Pc134) and scored using two widely used methods, developed by Bosland and Lindsey and by Black. The rating system developed by Bosland and Lindsey resulted in slightly higher logarithm of odds for the QTL on chromosome 5, and we detected a QTL on chromosome 12 uniquely using this rating system. A QTL on chromosome 10 was detected using both rating systems, but Black resulted in considerably higher logarithm of odds for this QTL compared with the Bosland and Lindsey system. Molecular markers developed were nominally better at accurately predicting the phenotype than previously published molecular markers but did not completely explain resistance in our validation populations. The inheritance pattern of resistance in one of our F2 populations did not significantly deviate from a 7:9 segregation ratio, indicating duplicative recessive epistasis. However, these results could be confounded by the presence of incomplete gene action, which was found through the improved selection accuracy when the phenotypes of heterozygous individuals were grouped with those with susceptible alleles.

Genetic analysis of the content of palmytic acid glycerides in the carriers of maize mutation shrunken-1

Aim. The influence of corn shrunken-1 (sh1) mutation on the content of palmitate in corn oil establishing and genetic analysis of this trait. Methods. The effects of the sh1 mutation on the content of palmitate were determined by comparing the inbreds – carriers of this mutation with inbreds of the common type, as well as in the top-crosses of common type inbreds with the mutant inbreds. The genetic components of the variance in terms of the content of palmitate were analyzed in the diallel crosses of mutant inbreds according to the second Griffing method. The determination of oil fatty acid composition was carried out by the Peisker gas chromatographic method. Results. It has been established that the corn inbreds – carriers of sh1 mutation exceed the common type inbreds by an average of 29.2 % in terms of palmitate content. The level of the trait in the inbreds based on the sh1 mutation was notable as having the quantitative variability and varied within 12.2-15.6 %. The content of palmitate in the carriers of sh1 mutation was inherited as incomplete dominance with a predominant contribution of additive effects to the variance. A higher level of the trait was controlled by recessive alleles of polygenes. Conclusions. The obtained results suggests the possibility of spatial linkage of the sh1 mutant gene with palmitate-coding locus, the effect of which is modified by the polygenic complex. It has been confirmed, that the carriers of sh1 mutation expands the genetic diversity of corn in terms of palmitate content.

Creation and analysis of the starting material obtained by hybridisation of Triticum spelta L. × Triticum compactum Host.

In the conducted studies, as a result of the hybridisation of Triticum spelta L. × Triticum compactum Host. several new forms were obtained that differ in morphobiological and economically valuable traits. The research aims to expand the genetic diversity of spelt wheat and to obtain new introgressive forms with a high level of manifestation of economically valuable traits. The following methods were used: field, laboratory, hydrological analysis, and statistical analysis. As a result of the research, new source material was obtained and valuable genotypes with a unique combination of genetic material of the source species were identified. An intermediate type of inheritance of plant morphology traits (plant height, ear length and density, grain weight per ear) in F1 hybrids was established. In F2 hybrids, a split of 3:1, indicates the dominant monogenic nature of inheritance. The shape of the ear is inherited monogenically by the type of incomplete dominance. The analysis of transgressive variability in F3-4 hybrids Triticum spelta L. × Triticum compactum Host. shows that the highest proportion of positive transgressions was recorded for the number of spikelets (28.1-28.5%) and grains (23.4-51.0%) in the ear and grain weight per spikelet (20.3-32.1%). The analysis of stability and adaptability indices allowed us to distinguish line 201, characterised by high stability (S2 di=0.027), homeostasis (Hom=193.3) and breeding value (Sc=3.9), and line 206, combining high yield (5.11 t/ha) with high homeostasis (Hom=182.3) and breeding value (Sc=3.9). The introgressive hybridisation with Triticum compactum Host. identified new genetic sources characterised by the presence of deficient traits for breeding and of great practical importance for further breeding and genetic improvement of spelt, as they can enrich the existing gene pool of the crop

Genetic analysis of the 1000 grain weight trait in interlinear hybrids of winter rye (secale cereale l.)

The aim of the study is to quantify the contribution of additive, dominant and epistatic dispersions to the overall genetic variation of the 1000 grain weight trait to increase the efficiency of breeding heterotic hybrids of winter rye. The experiments were carried out at the experimental base of the Federal Research Center «Nemchinovka» (Moscow region). The starting material was 10 male sterile homozygous inbred lines carrying the Pump-type cytoplasm. These lines were crossed with two male fertile test lines: mf H-842 and mf H-1247. Test crosses were carried out in 2019 on two isolated plots according to the topcross scheme. The resulting hybrids and their parent forms were tested in 2020 and 2021 on plots of 8 m2 in two-fold repetition. The test for epistasis and decomposition of the genetic varianсе into additive and dominant components was carried out by the method of Jinks J., Perkins L.M., Brees E.L. (1969). The data show that the additive interaction of genes, as well as incomplete dominance, plays the main role in determining the trait of granularity. A stable ratio of these interactions was established over the years: the proportion of additive effects varied at the level of 83.9-84.7%, and the proportion of dominant effects at the level of 15.3-16.1%. The indicator of the degree of dominance √(H1/D) was less than one and varied slightly over the years. It follows from this that dominant alleles affecting gross grain do not completely suppress the effect of their recessive alleles. For this reason, simple interlinear hybrids inherit an intermediate phenotype compared to the parent forms. The most coarse-grained hybrids were obtained by crossing lines ms H-1054, ms H-649 and ms H-1090 with the coarsegrained tester mf H-1247. It is concluded that, in the synthesis of commercial rye hybrids, it is necessary to strive to ensure that all parent forms are gross-grained. To obtain such lines it is advisable to use methods of recurrent selection as well as convergent and cumulative breeding.

Pyridaben resistance, inheritance and target site mutations in Neoseiulus californicus (McGregor) (Acari: Phytoseiidae)

ABSTRACT The predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is a key natural enemy applied in phytophagous mite control in agricultural production areas. This study is aimed at investigating the development of pyridaben resistance as a result of the selection pressure under laboratory conditions on N. californicus mites, the inheritance of pyridaben resistance in this predatory mite, and the relationship of resistance with target region mutations. Pyridaben resistance levels were evaluated using a leaf disc spraying tower method. As a result of seven selections, 270-fold pyridaben resistance was identified in N. californicus. As a result of inheritance studies, pyridaben resistance in F1 females resulted from incomplete dominance and sex. Neoseiulus californicus was resistant to pyridaben and there was no significant difference in the monooxygenase enzyme levels in respect to the initial population. No amino acid changes were detected in the PCR evaluations of target site mutations in the pyridaben-resistant and initial populations of N. californicus. Increased pyridaben resistance in the selected population was thought to be caused by more mechanisms other than target site mutations.