F1 Hybrids Research Articles

Mycotoxin zearalenone induces multi-/trans-generational toxic effects and germline toxicity transmission via histone methyltransferase MES-4 in Caenorhabditis elegans

Zearalenone (ZEN), an endocrine-disrupting mycotoxin, is prevalent and persists in the environment. ZEN has the potential to cause adverse health impacts extending over generations, yet there is a lack of relevant research. Therefore, we explored the ZEN-induced multi-/trans-generational locomotive and reproductive toxicities, as well as the underlying epigenetic mechanisms in Caenorhabditis elegans. In multi-generational analysis, the evolution tendency and toxicity latency were observed under sustained exposure to 0.1 and 1 μM ZEN across five generations (P0-F4). The toxic effects were found in filial generations even if the initial parental exposure showed no apparent effects. Trans-generational results indicated the toxic inheritance phenomenon of 10 and 50 μM ZEN, where a single generation of ZEN exposure was sufficient to affect subsequent generations (F1-F3). Additionally, the pattern of locomotion was relatively sensitive in both generational studies, indicating varying sensitivity between indicators. Regarding epigenetic mechanism of toxicity transmission, ZEN significantly decreased the parental expression of histone methyltransferase encoded genes set-2, mes-2, and mes-4. Notably, the downregulation of mes-4 persisted in the unexposed F1 and F2 generations under trans-generational exposure. Furthermore, the mes-4 binding and reproduction-related rme-2 also decreased across generations. Moreover, parental germline specific knockdown of mes-4 eliminated the inherited locomotive and reproductive toxic effects in offspring, showing that mes-4 acted as transmitter in ZEN-induced generational toxicities. These findings suggest that ZEN is an epigenetic environmental pollutant, with a possible genetic biomarker mes-4 mediating the germline dependent transmission of ZEN-triggered toxicity over generations. This study provides significant insights into ZEN-induced epigenotoxicity.

Comparison of Six Measures of Genetic Similarity of Interspecific Brassicaceae Hybrids F2 Generation and Their Parental Forms Estimated on the Basis of ISSR Markers.

Genetic similarity determines the extent to which two genotypes share common genetic material. It can be measured in various ways, such as by comparing DNA sequences, proteins, or other genetic markers. The significance of genetic similarity is multifaceted and encompasses various fields, including evolutionary biology, medicine, forensic science, animal and plant breeding, and anthropology. Genetic similarity is an important concept with wide application across different scientific disciplines. The research material included 21 rapeseed genotypes (ten interspecific Brassicaceae hybrids of F2 generation and 11 of their parental forms) and 146 alleles obtained using 21 ISSR molecular markers. In the presented study, six measures for calculating genetic similarity were compared: Euclidean, Jaccard, Kulczyński, Sokal and Michener, Nei, and Rogers. Genetic similarity values were estimated between all pairs of examined genotypes using the six measures proposed above. For each genetic similarity measure, the average, minimum, maximum values, and coefficient of variation were calculated. Correlation coefficients between the genetic similarity values obtained from each measure were determined. The obtained genetic similarity coefficients were used for the hierarchical clustering of objects using the unweighted pair group method with an arithmetic mean. A multiple regression model was written for each method, where the independent variables were the remaining methods. For each model, the coefficient of multiple determination was calculated. Genetic similarity values ranged from 0.486 to 0.993 (for the Euclidean method), from 0.157 to 0.986 (for the Jaccard method), from 0.275 to 0.993 (for the Kulczyński method), from 0.272 to 0.993 (for the Nei method), from 0.801 to 1.000 (for the Rogers method) and from 0.486 to 0.993 (for the Sokal and Michener method). The results indicate that the research material was divided into two identical groups using any of the proposed methods despite differences in the values of genetic similarity coefficients. Two of the presented measures of genetic similarity (the Sokal and Michener method and the Euclidean method) were the same.

Salvia multicaulis × Salvia officinalis hybridization: Changes in the phenolic and essential oil profiles, gene expression and biological activity under Saint Catherine conditions—Egypt

The Salvia genus, particularly the wild genotypes, received significant attention due to its antibacterial, antioxidant, antiviral, and anticancer properties. Crossbreeding wild and cultivated plants can conserve the genetic resources of wild plants and develop new hybrids with high yields and high resistance to climatic changes. In this study, Salvia multicaulis (P1, wild) and Salvia officinalis (P2, cultivated) have been crossed to produce a novel hybrid (F1 hybrid) in the Saint Catherin protectorate - Egypt. In P1, P2, and F1 hybrid, heterosis, phytochemical composition, gene expression of PAL (Phenylalanine ammonia-lyase), RAS1 (Rosmarinic acid synthase I), CYP (Cytochrome P450), and CS (1,8-Cineole synthase), besides antioxidant, anticancer, anti-inflammatory, and antibacterial effects were assessed. The F1 hybrid recorded the highest means of plant height in the two seasons. Heterosis over the mid-parents was positively associated with various traits, including stem thickness, number of branches, fresh yield, and percentage of oil in both seasons. Total phenolic and flavonoid content were found in the following order: P2 > P1 > F1. DPPH antioxidant effect was found in the following order: P2 > F1 > P1. The F1 hybrid had the highest content of rosmarinic acid (12.379 mg/g), quercetin (0.595 mg/g), and naringenin (0.152 mg/g), followed by P1 and P2. The 1,8-cineol and α-pinene were the main compounds in the essential oils of P1, P2, and F1. The 1,8-cineol was found in the following order: P2 > F1 > P1, while α-pinene was found in the following order: P1 > F1 > P2. The RAS1 expression showed a weak correlation with the concentration of rosmarinic acid, while the expressions of PAL and CYP were strongly correlated with the concentrations of main phenolics, including rosmarinic acid, quercetin, and naringenin. The 1,8-cineol content was negatively correlated with the expression of the CS gene. The P2 extract and the F1 hybrid essential oil showed potent anticancer, anti-inflammatory, and antibacterial properties. Crossbreeding S. multicaulis (P1, wild) and S. officinalis (P2, cultivated) in this study developed a new hybrid (F1) with good growth characteristics, high essential oil yields, high levels of bioactives, and good bioactivity. This makes it suitable for large-scale production for use in food and pharmaceutical applications.

Performance of Provitamin a Maize Hybrids for Yield and Desirable Agronomic Traits

To find improved F1 hybrids for breeding procedures, the heterosis of maize hybrids must be determined. Therefore, to identify prospective hybrids for use in future provitamin A maize breeding systems, this study was carried out to evaluate the amount of standard heterosis for grain yield and related attributes. Fifteen provitamin A maize inbred lines were crossed through the diallel-II design. The resulting Eight four F1 hybrids along with four standard checks (BHQPY545, BH549, BH546, and BH547) were evaluated using RCBD (20 entries) and Alpha-Lattice Design (68 entries) with two replications during 2022/2023 main cropping season at Bako National Maize Research Center. Analysis of variance revealed significant variations for most of the traits indicating the existence of genetic variability. The Standard heterosis assessment noticed significant positive and negative heterosis for the majority of the traits investigated. Cross combinations over BHQPY 545, such as L10 × L3, L10 × L6, and L13×L12, demonstrated the largest proportion of traditional heterosis for grain yield (more than 25% yield advantage). Because BH546 and BH547 are normal maize with grain production potential, the majority of crossings yielded negative and significant results over commercial checks. The highest found heterosis for grain yield and associated factors indicated that maize genotypes' heterotic potential may be beneficial to boost yield. The findings of this study could be valuable for researchers looking to develop high-yielding provitamin A maize hybrids. As a result, possible hybrids might be recommended for commercial usage once the results have been verified by repeating the research over time and across places, as well as incorporating quality attributes analysis data.

A Survey of Fruit Quality Properties, Growth, and Yield of Several Melon Varieties (<i>Cucumis melo</i> L.) Using Fertigation Approach

Melons, <i>Cucumis melo</i> L., belongs to the family Cucurbitaceae. They are popular for their sweet, juicy fruit flesh with pleasant aroma. These melons are packed with numerous essential nutrients for the human body. In this study, the fruit quality properties, growth, and yield of nine different melon varieties were compared via a fertigation approach to deduce the best melon variety to be planted by melon farmers. Quantitative and qualitative traits of all nine melon varieties were collected and compared. As a result, it was discovered that the Japanese Rock Melon F1 Hybrid is an all-rounder best melon variety, with the highest seed germination percentage and fruiting percentage. On the other hand, the Sweet Green Melon F1 can also be considered the second-best choice, but the only downside is that the germination rate is significantly lower compared to others, at merely 37%. Hopefully, this study can serve as a foundation for developing a more comprehensive database for melon varieties to aid melon farmers in decision-making and further improve the industry’s yield.

Analyzing Genetic Variation and Graphical Representation (Wr-Vr) in Brinjal (Solanum melongena L.) using the Hayman Approach in the Northwestern Region of India

Background: Brinjal, also known as eggplant, is a resilient and widely cultivated vegetable crop in the Solanaceae family. It plays a crucial role in diets due to its rich supply of vitamins, minerals and dietary fiber, helping address the deficit in vegetable consumption recommended by the World Health Organization (WHO), which advises a daily intake of at least 400 grams of fruits and vegetables. Estimating genetic parameters is essential for understanding the genetic architecture of yield and its determining factors. Hayman’s diallel cross analysis method is extensively utilized in plant breeding due to its capacity to provide comprehensive insights into diverse genetic parameters, including gene action, degree of dominance and heritability. Methods: Nine parents with thirty six F1 hybrids of brinjal derived using a half diallel mating design with nine brinjal genotypes, namely JBL-1, JBR-1, JBR-2, JBR-3, JBL-2, JBL-3, JBR-4, JBR-5 and JBR-6 were evaluated for yield and other yield attributing traits during kharif season 2023) using randomized block design (RBD) with three replications. Result: The dominance effect (H1) was significant and displayed a greater magnitude, indicating dominance gene action for yield per plant. The regression coefficient slope showed a significant deviation from zero, but not from unity, indicating the absence of non-allelic interaction. Furthermore, the regression line intersected the Wr axis below the origin, suggesting the presence of over-dominance for days to 50% flowering, fruit length (cm), number of primary branches per plant, plant height (cm), total fruit yield per plant (kg) and fruit borer infestation (%). The mean degree of dominance exceeding one indicated the prevalence of over-dominance for all traits except days to first picking, average fruit weight (gm), fruit girth (cm) and number of fruits per plant. These findings emphasize the importance of dominance variation in eggplant improvement, enabling successful heterosis breeding for advancing these populations and development of hybrids.

Combining Ability and Heterosis for Yield and Yield Attributing Traits in Bitter Gourd

A study was conducted during Rabi 2022 and Kharif 2023 at the Department of Horticulture, University of Agricultural Sciences, Bangalore to develop 49 F1 hybrids through the utilization of line × tester mating design. The parents and developed hybrids along with standard check (Pusa Hybrid 6) were evaluated in Randomized Complete Block Design) and Alpha lattice design, respectively, for yield and yield attributing traits. The combining ability analysis revealed that among 14 parents, Pusa Rasdar, Pusa Do Mausami, Pusa Vishesh, Hirkani and Pant Karela 4 were identified as best general combiners for most of the studied yield and yield attributing traits. The estimates of heterosis revealed that the hybrids, Konkan Karali × Pant Karela 4 (45.45%), Konkan Tara × Pusa Do Mausami (23.48%), Pusa Rasdar × Phule Green Gold (126.87%) and Hirkani × Pusa Do Mausami (46.20%) were top performing hybrids over standard check for fruit length, diameter, average weight and number of fruits per vine, respectively. Similarly, Pusa Rasdar × Pant Karela 4 (127.06%), Priya × Pusa Do Mausami (101.05%), Punjab 14 × Pusa Do Mausami (100.53%) and Pusa Rasdar × Pant Karela 3 (97.61%) were top performing hybrids over standard check for yield per vine. These hybrids also recorded highest significant sca effects hence, considered as good specific combiners.

Upregulation of PECTATE LYASE5 by a NAC transcription factor promotes fruit softening in apple.

Flesh firmness is a critical breeding trait that determines consumer selection, shelf life, and transportation. The genetic basis controlling firmness in apple (Malus×domestica Borkh.) remains to be fully elucidated. We aimed to decipher genetic variance for firmness at harvest and develop potential molecular markers for marker-assisted breeding. Maturity firmness for 439 F1 hybrids from a cross of 'Cripps Pink' and 'Fuji' was determined in 2016 and 2017. The phenotype segregated extensively, with a Gaussian distribution. In a combined bulked segregant analysis (BSA) and RNA-sequencing analysis, eighty-four differentially expressed genes were screened from the 10 QTL regions. Interestingly, next-generation re-sequencing analysis revealed a Harbinger-like transposon element insertion upstream of the candidate gene PECTATE LYASE5 (MdPL5); the genotype was associated with flesh firmness at harvest. The presence of this transposon repressed MdPL5 expression and was closely linked to the extra-hard phenotype. MdPL5 was demonstrated to promote softening in apples and tomatoes. Subsequently, using the MdPL5 promoter as bait, MdNAC1-L was identified as a transcription activator that positively regulates ripening and softening in the developing fruit. We also demonstrated that MdNAC1-L could induce the up-regulation of MdPL5, MdPG1, and the ethylene-related genes MdACS1 and MdACO1. Our findings provide insight into TE-related genetic variation and the PL-mediated regulatory network for the firmness of apple fruit.

Insights into cellular crosstalk regulating cytoplasmic male sterility and fertility restoration.

Cytoplasmic male sterility has been a popular genetic tool in development of hybrids. The molecular mechanism behind maternal sterility varies from crop to crop. An understanding of underlying mechanism can help in development of new functional CMS gene in crops which lack effective and stable CMS systems. In crops where seed or fruit is the commercial product, fertility must be recovered in F1 hybrids so that higher yield gains can be realized. This necessitates the presence of fertility restorer gene (Rf) in nucleus of male parent to overcome the effect of sterile cytoplasm. Fertility restoring genes have been identified in crops like wheat, maize, sunflower, rice, pepper, sugar beet, pigeon pea etc. But in crops like eggplant, bell pepper, barley etc. unstable fertility restorers hamper the use of Cytoplasmic genic male sterility (CGMS) system. Stability of CGMS system is influenced by environment, genetic background or interaction of these factors. This review thus aims to understand the genetic mechanisms controlling mitochondrial-nuclear interactions required to design strong and stable restorers without any pleiotropic effects in F1 hybrids.

Genetic Dissection of ToLCNDV Resistance in Resistant Sources of Cucumis melo.

Tomato leaf curl New Delhi virus (ToLCNDV) is a begomovirus causing significant melon (Cucumis melo) crop losses globally. This study aims to map the ToLCNDV resistance in the PI 414723 melon accession, previously identified and characterized through phenotypic studies, thereby exploring shared genomic regions with the established resistant source WM-7. In the present study, WM-7 and PI 414723 were crossed with the susceptible accessions 'Rochet' and 'Blanco' respectively, to generate F1 hybrids. These hybrids were self-pollinated to generate the populations for mapping the ToLCNDV resistance region and designing markers for marker-assisted selection. Disease evaluation included visual symptom scoring, viral-load quantification and tissue printing. Genotyping-by-sequencing and SNP markers were used for quantitative trait loci (QTL) mapping. For genetic analysis, qPCR and bulked segregant RNA-seq (BSR-seq) were performed. Gene expression was assessed using RNA-seq, and qRT-PCR was used for confirmation. The research narrows the candidate region for resistance in WM-7 and identifies overlapping QTLs on chromosome 11 in PI 414723, found in the region of the DNA primase large subunit. BSR-seq and expression analyses highlight potential regulatory roles of chromosome 2 in conferring resistance. Differential expression was confirmed for six genes in the candidate region on chromosome 2. This study confirms the existence of common resistance genes in PI 414723 and WM-7.

Recordings of Superior Laryngeal Nerve Sensory Nerve Action Potentials in a Rat Model.

Superior laryngeal nerve (SLN) function is critical to laryngeal sensation. Sensory dysfunction in the larynx, mediated through the internal branch of the superior laryngeal nerve (iSLN), is thought to occur with aging and neurodegenerative disease. However, objective analysis of iSLN neurophysiology is difficult due to its anatomic location and small diameter. This study measures sensory nerve action potentials (SNAP) from the iSLN in a rat model. SNAP data were obtained from two adult rat strains (Sprague-Dawley, SD and Fischer 344 × Brown Norway F1 Hybrid rats, FBN). Evoked responses were obtained by stimulating the main trunk of the SLN and recording the response using a 160-μm cuff electrode placed around the iSLN. SNAP were averaged from 10 stimulations. Laryngeal adductor reflex (LAR) threshold measurements were obtained with stimulation of the iSLN and direct laryngoscopy. The sections of the iSLN were obtained for histologic analysis. SLN-evoked responses were successfully obtained in 18 hemi-laryngeal preparations (SD n = 13 and FBN n = 5) with corresponding LAR threshold measurements. Mean(±SD) SNAP latency, total duration, amplitude, negative durations, and intensity were 2.28 ms (±0.56), 2.13 ms (±0.70), 879 μV (±535), and 0.69 mA (±0.25), respectively. SLN stimulation threshold to elicit an LAR was of 0.84 mA (±0.31). It is feasible to record evoked SLN responses in two adult rat strains. This work may lead to a tractable animal model for objective measurements of SLN neurophysiology with various disease states. N/A Laryngoscope, 2024.

Wheat Cybrid Plants, OryzaWheat, Regenerated from Wheat-Rice Hybrid Zygotes via in Vitro Fertilization System Possess Wheat-Rice Hybrid Mitochondria.

Hybridization generates biodiversity, and wide hybridization plays a pivotal role in enhancing and broadening the useful attributes of crops. The hybridization barrier between wheat and rice, the two most important cereals, was recently overcome by in vitro production of allopolyploid wheat-rice hybrid zygotes, which can develop and grow into mature plants. In the study, genomic sequences and compositions of the possible hybrid plants were investigated through short- and long-read sequencing analyses and fluorescence in situ hybridization (FISH)-based visualization. The possible hybrid possessed whole wheat nuclear and cytoplasmic DNAs and rice mitochondrial (mt) DNA, along with variable retention rates of rice mtDNA ranging from 11% to 47%. The rice mtDNA retained in the wheat cybrid, termed Oryzawheat, can be transmitted across generations. In addition to mitochondrial hybridization, translocation of rice chromosome 1 into wheat chromosome 6A was detected in a F1 hybrid individual. OryzaWheat can provide a new horizon for utilizing inter-subfamily genetic resources among wheat and rice belonging to different subfamilies, Pooideae and Ehrhartoideae, respectively.

Genetic background affects the strength of crossover interference in house mice.

Meiotic recombination is required for faithful chromosome segregation in most sexually reproducing organisms and shapes the distribution of genetic variation in populations. Both the overall rate and the spatial distribution of crossovers vary within and between species. Adjacent crossovers on the same chromosome tend to be spaced more evenly than expected at random, a phenomenon known as crossover interference. Although interference has been observed in many taxa, the factors that influence the strength of interference are not well understood. We used house mice (Mus musculus), a well-established model system for understanding recombination, to study the effects of genetics and age on recombination rate and interference in the male germline. We analyzed crossover positions in 503 progeny from reciprocal F1 hybrids between inbred strains representing the three major subspecies of house mice. Consistent with previous studies, autosomal alleles from M. m. musculus tend to increase recombination rate, while inheriting a M. m. musculus X chromosome decreases recombination rate. Old males transmit an average of 0.6 more crossovers per meiosis (5.0%) than young males, though the effect varies across genetic backgrounds. We show that the strength of crossover interference depends on genotype, providing a rare demonstration that interference evolves over short timescales. Differences between reciprocal F1s suggest that X-linked factors modulate the strength of interference. Our findings motivate additional comparisons of interference among recently diverged species and further examination of the role of paternal age in determining the number and positioning of crossovers.

Pervasive tissue-, genetic background-, and allele-specific gene expression effects in Drosophila melanogaster.

The pervasiveness of gene expression variation and its contribution to phenotypic variation and evolution is well known. This gene expression variation is context dependent, with differences in regulatory architecture often associated with intrinsic and environmental factors, and is modulated by regulatory elements that can act in cis (linked) or in trans (unlinked) relative to the genes they affect. So far, little is known about how this genetic variation affects the evolution of regulatory architecture among closely related tissues during population divergence. To address this question, we analyzed gene expression in the midgut, hindgut, and Malpighian tubule as well as microbiome composition in the two gut tissues in four Drosophila melanogaster strains and their F1 hybrids from two divergent populations: one from the derived, European range and one from the ancestral, African range. In both the transcriptome and microbiome data, we detected extensive tissue- and genetic background-specific effects, including effects of genetic background on overall tissue specificity. Tissue-specific effects were typically stronger than genetic background-specific effects, although the two gut tissues were not more similar to each other than to the Malpighian tubules. An examination of allele specific expression revealed that, while both cis and trans effects were more tissue-specific in genes expressed differentially between populations than genes with conserved expression, trans effects were more tissue-specific than cis effects. Despite there being highly variable regulatory architecture, this observation was robust across tissues and genetic backgrounds, suggesting that the expression of trans variation can be spatially fine-tuned as well as or better than cis variation during population divergence and yielding new insights into cis and trans regulatory evolution.

Growth, Yield, and Physiological Responses of Cucumber (Kish F1 Hybrid) Grafted onto African Horned Cucumber (Cucumis metuliferus L.) Rootstock under Deficit Irrigation Stress

Growth, Yield, and Physiological Responses of Cucumber (Kish F1 Hybrid) Grafted onto African Horned Cucumber (Cucumis metuliferus L.) Rootstock under Deficit Irrigation Stress

QTL mapping and candidate gene identification for lower temperature tolerance and growth traits using whole genome re-sequencing in Argopecten scallops

Lower temperature tolerance (LTT) and growth traits are vital to the success of overwintering scallop farming in the North China Sea. Bohai Red, a novel selected scallop strain is the main aquaculture species in this region. However, its poor LTT hinders its growth. To improve these traits, the larger Bohai Red scallop was crossed with the smaller bay scallop (A. irradians irradians) which tolerates low temperatures. The full-sib F1 hybrids and the whole-genome resequencing (WGR) method were used to construct a high-density genetic linkage map comprising 5925 single nucleotide polymorphisms (SNPs). The consensus linkage map consisted of 16 linkage groups spanning 1343.46 cM with an average distance of 0.23 cM. Based on this genetic linkage map, 42 potentially significant quantitative trait loci (QTLs) for LTT and growth were detected in eight different linkage groups (LGs) explaining 9.2–18.6% of the phenotypic variation. LG11 may regulate both LTT and growth as 20 QTLs were localized there. Eighteen candidate genes were identified, including 2 (SCARF1, SLC28A3) for LTT and 16 for the growth-related traits. To the best of our knowledge, the present work is one of the first to fine-map the LTT and growth-related QTLs in a genetic linkage map for hybrid Argopecten spp. scallops.

Development of Apomictic 56-Chromosomal Maize-Tripsacum Hybrids: A Potential Breakthrough in Heterosis Fixation.

Maize (Zea mays L.) is one of the most demanded grain crops in the world. Currently, production has exceeded one billion tons and is increasing by 3-5% annually. Such growth is due to the genetic potential of the crop and the use of heterosis F1 hybrids in production. However, the need to produce first-generation seed annually poses significant challenges and is an economically costly technology. A solution to this problem may be the transfer of the asexual (apomictic) mode of reproduction to maize from its wild relative, eastern gamagrass (Tripsacum dactyloides L.). In this work, we report the production of 56-chromosome apomictic hybrids of maize (Zea mays L.) with eastern gamagrass (T. dactyloides L.) with restored anther fertility. The mode of reproduction of the plant was confirmed by counting chromosomes and sequencing the nuclear gene (Pox3) and chloroplast tRNA-Leu (trnL) gene. These apomictic hybrids had karyotypes of 2n = 56 = [(10Zm(573MB) + 36Td) + 10Zm(611CB)] and 2n = 56 = [(10Zm(611CB) + 36Td) + 10Zm(611CB)]. The resulting hybrids can be widely used as a fodder crop.

Phenotypic covariation predicts diversification in an adaptive radiation of pupfishes.

Phenotypic covariation among suites of traits may constrain or promote diversification both within and between species, yet few studies have empirically tested this relationship. In this study, we investigate whether phenotypic covariation of craniofacial traits is associated with diversification in an adaptive radiation of pupfishes found only on San Salvador Island, Bahamas (SSI). The radiation includes generalist, durophagous, and lepidophagous species. We compared phenotypic variation and covariation (i.e., the P matrix) between (1) allopatric populations of generalist pupfish from neighboring islands and estuaries in the Caribbean, (2) SSI pupfish allopatric lake populations with only generalist pupfish, and (3) SSI lake populations containing the full radiation in sympatry. Additionally, we examine patterns observed in the P matrices of two independent lab-reared F2 hybrid crosses of the two most morphologically distinct members of the radiation to make inferences about the underlying mechanisms contributing to the variation in craniofacial traits in SSI pupfishes. We found that the P matrix of SSI allopatric generalist populations exhibited higher levels of mean trait correlation, constraints, and integration with simultaneously lower levels of flexibility compared to allopatric generalist populations on other Caribbean islands and sympatric populations of all three species on SSI. We also document that while many craniofacial traits appear to result from additive genetic effects, variation in key traits such as head depth, maxilla length, and lower jaw length may be produced via non-additive genetic mechanisms. Ultimately, this study suggests that differences in phenotypic covariation significantly contribute to producing and maintaining organismal diversity.

Maize breeding effects on grain yield genetic progress and its contribution to global yield gain in Argentina

Context or problemMaize production in Argentina has increased in recent years, following the global gain (GG) in grain yield (GY). The GG in GY depends on genetic progress (GP), which requires frequent quantification to detect potential plateaus and variations in its contribution to the GG. In this sense, hybrid adoption in Argentina shifted from double- and three-way to single cross (F1) hybrids in the 1990s, thereby increasing the level of heterosis of released hybrids. Since heterosis increase may have had a greater impact on estimates of maize GG than those based on a single cross type, GP based exclusively on F1 hybrids and its contribution to GG could be lower than that including different types of crosses. Objective or research questionThe main objectives of this work were to (i) analyze grain yield GP, (ii) dissect grain yield GP into the corresponding trends in its physiological determinants and numerical components, and (iii) estimate the relative contribution of GP to GG in the main maize producing region of Argentina for the period marked by significant changes in heterosis level (i.e. from 1960s to 1990s) and the period of massive adoption of F1 hybrids (from 1990s onwards). MethodsWe used a dataset obtained at the core of the mentioned region (INTA Pergamino; 33°56’S, 60°34’W) from era-decade experiments (ERA) including 24 hybrids released between 1965 and 2016 and grown with no abiotic or biotic restrictions. We quantified GY, its numeric components (KN: kernel number m−2, KW: individual kernel weight) and its physiological determinants (BT: total shoot biomass at maturity, HI: harvest index). ResultsA GP of 0.84 % y−1 was computed for GY from 1965 to 1993, and of 0.51 % y−1 thereafter. We also detected genetic progress for KN (0.53 % y−1) and BT (0.26 % y−1) but not for KW. A GP of 0.66 % y−1 was computed for HI up to 1993, which plateaued thereafter. A 40 % contribution of GP to GG was estimated for the Pergamino site from 1965 to 1993, predominantly driven by changes in heterosis level. The contribution dropped to 32 % from 1993 onwards, when F1 hybrids were massively adopted by the farmers. This contribution was much smaller (e.g. 19 %) in areas less representative of the target population of environments of dominant breeding programs. ConclusionsOur findings underline that the relative contribution of GP to GY improvement at the regional level varies markedly depending upon the period included in the analysis and the environment used for evaluation. The decline observed at less representative locations of the main target population of environments may guide breeders in their decision for developing new programs.

The course of tuberculosis infection in hyper-susceptible mice carrying the <i>H2</i>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.