F1 Hybrids Research Articles

Genetic Response of Selected Maize Genotypes to Gray Leaf Spot (Cercospora zeina L.) Infestation

Gray leaf spot (GLS) caused by Cercospora zea-maydis and Cercospora zeina is one of the most yield limiting diseases of maize globally. Yield losses of up to 60 percent in susceptible genotypes are not uncommon. The objectives of the study were to evaluate the response of diverse maize genotypes to Gray leafspot infestation in western Kenya; determine the genetics of GLS resistance in maize inbred lines CML312, CML389 and to evaluate the relationship between GLS assessment methods, severity and lesion length. 13 maize inbred lines, 2F1 hybrids, and F2 populations of crosses MSN21 and CML389 or CML312 were evaluated under artificial GLS infestation during the 2007/08 seasons at Maseno university. Among the inbred lines, MSN21 was the most susceptible to GLS and had the highest disease severity rating. The inbred line CML389 and their F1 hybrids showed high levels of GLS resistance. CML312 and CML384 showed tolerance to GLS. Correlation between the lesion length and severity ratings was positive and highly significant (r = 0.9; P < 0.001), suggesting that both could be used in disease damage assessment. The frequency distribution of severity data for the F2 population of a cross between MSN21 and CML312 was continuous, suggesting that GLS tolerance is influenced by quantitative genes. A similar frequency distribution data for F2 population of a cross between MSN21 and CML389, showed 2 distinct peaks, and the genotypes within the 2 classes fitted a 9 to 7 ratio. This suggests that the resistance to GLS in CML389 may be conditioned by at least 2 major genes, with complementary epistatic interactions.

Usefulness of alien sterilizing cytoplasms for the hybrid breeding of triticale (xTriticosecale Wittmack): preliminary results.

To be useful for cereal breeding, cytoplasmic male sterility (CMS) should express the complete sterility of maternal lines and the full restoration of the male fertility of F1 hybrids. The most reliable source of sterilizing cytoplasm for triticale is Triticum timopheevi; however, due to the low frequency of efficient non-restorer genotypes for this cytoplasm, new sources of CMS are needed. In this study, aside from T. timopheevi (T) cytoplasm, three alternative CMS sources were tested: Pampa (P) from Secale cereale L., Aegilops sharonensis (A), and Ae. ventricosa (V). The suitability of these cytoplasms for breeding was assessed based on the male fertility/sterility of F1 hybrids obtained through the manual pollination of CMS maternal lines with 36 triticale cultivars and breeding strains. About half of the hybrids with each type of cytoplasm were fully fertile and produced more than 30 grains per bagged spike. The highest percentage was found in hybrids with P cytoplasm (58.33%) and the lowest in hybrids with A cytoplasm (44.44%). Male sterility was observed in hybrids with P cytoplasm (16.67%) and A cytoplasm (16.67%) but not in hybrids with T or V cytoplasm. In terms of practical aspects, male sterility systems with P or A cytoplasm exhibit similarity in their ability to restore male fertility that differ from the T and V cytoplasms. Although all studied cytoplasms exhibited some disadvantages for breeding purposes, none should be definitively classified as unacceptable for future breeding programs regarding the development of triticale hybrid cultivars.

Exploring Genetic Variability Parameters for Yield and Quality Traits in Urdbean Genotypes and Its Triple Test Cross F1 Hybrids

Exploring Genetic Variability Parameters for Yield and Quality Traits in Urdbean Genotypes and Its Triple Test Cross F1 Hybrids

Indirect evaluation of watermelon volatile profile: Detection of subtle changes with e-nose systems

The effectiveness of e-nose systems as high-throughput tools for volatile profiling in watermelon was investigated focusing on discerning subtle changes induced by the use of different rootstocks. Partial Least Square Discriminant Analysis (PLS-DA) models, both GC-MS and e-nose data, demonstrated moderate performance in classification due to nuanced differences among groups (the same F1 hybrid was used as scion). However, PLS-DA biplots revealed a clear correlation between GC-MS and e-nose data. This methodology enabled the e-nose system to identify the effects of specific root-scion combinations compared to non-grafted controls and detect combinations with more variable volatile profiles. Remarkably, the e-nose system identified samples with anomalous volatile profiles, mirroring the capabilities of GC-MS data. Additionally, PLS models were developed to provide reasonably accurate predictions of key compound contents like geranylacetone, (Z)-6-nonen-1-ol, or (Z)-6-nonenal, crucial for watermelon flavor and taste perception. Overall, this study highlights the potential of e-nose systems in discerning nuanced variations in watermelon volatile profiles affecting aroma. Incorporating volatile profile evaluation capabilities using such systems will significantly optimize quality control processes and plant breeding programs.

Transcriptome analysis revealed differences in gene expression in sheep muscle tissue at different developmental stages

BackgroundThe analysis of differentially expressed genes in muscle tissues of sheep at different ages is helpful to analyze the gene expression trends during muscle development. In this study, the longissimus dorsi muscle of pure breeding Hu sheep (H), Suffolk sheep and Hu sheep hybrid F1 generation (SH) and East Friesian and Hu sheep hybrid sheep (EHH) three strains of sheep born 2 days (B2) and 8 months (M8) was used as the research object, and transcriptome sequencing technology was used to identify the differentially expressed genes of sheep longissimus dorsi muscle in these two stages. Subsequently, GO and KEGG enrichment analysis were performed on the differential genes. Nine differentially expressed genes were randomly selected and their expression levels were verified by qRT-PCR.ResultsThe results showed that 842, 1301 and 1137 differentially expressed genes were identified in H group, SH group and EHH group, respectively. Among them, 191 differential genes were enriched in these three strains, including pre-folding protein subunit 6 (PFDN6), DnaJ heat shock protein family member A4 (DNAJA4), myosin heavy chain 8 (MYH8) and so on. GO and KEGG enrichment analysis was performed on 191 differentially expressed genes shared by the three strains to determine common biological pathways. The results showed that the differentially expressed genes were significantly enriched in ribosomes, unfolded protein binding, FoxO signaling pathway, glycolysis / glycogen generation and glutathione signaling pathway that regulate muscle protein synthesis and energy metabolism. The results of qRT-PCR were consistent with transcriptome sequencing, which proved that the sequencing results were reliable.ConclusionsOverall, this study revealed the important genes and signaling pathways related to sheep skeletal muscle development, and the result laid a foundation for further understanding the mechanism of sheep skeletal muscle development.

Intersectional Hybrids between Darrow's Blueberry (V. darrowii Camp) and Lingonberry (V. vitis-idaea L.).

An initial cross of V. darrowii 'Johnblue' (Darrow's blueberry) × V. vitis-idaea 'Red Sunset' (lingonberry) produced more than 30 true intersectional diploid hybrids as confirmed by molecular markers. The most vigorous of these hybrids was extensively evaluated. This hybrid, US 2535-A, was floriferous and morphologically intermediate to the respective parents. Examination of pollen suggested low male fertility. Numerous crosses using the hybrid as a female reflected similarly low fertility and potential crossing barriers. Stylar examination suggested blockage of pollen tube growth in self-pollinations and significantly retarded growth in backcross pollinations. Nonetheless, two confirmed hybrid offspring were produced using the F1 hybrid as a female in crosses with V. vitis-idaea and V. darrowii, respectively. In a second set of crosses utilizing additional V. darrowii and V. vitis-idaea genotypes, another 23 verified hybrids in seven parental combinations were produced. Hybrids such as the ones presented offer the potential for generating de novo interspecific fruit types in blueberry and/or broadening the adaptation of lingonberry.

The role of mitochondria in sex- and age-specific gene expression in a species without sex chromosomes

Mitochondria perform an array of functions, many of which involve interactions with gene products encoded by the nucleus. These mitochondrial functions, particularly those involving energy production, can be expected to differ between sexes and across ages. Here, we measured mitochondrial effects on sex- and age-specific gene expression in parental and reciprocal F1 hybrids between allopatric populations of Tigriopus californicus with over 20% mitochondrial DNA divergence. Because the species lacks sex chromosomes, sex-biased mitochondrial effects are not confounded by the effects of sex chromosomes. Results revealed pervasive sex differences in mitochondrial effects, including effects on energetics and aging involving nuclear interactions throughout the genome. Using single-individual RNA sequencing, sex differences were found to explain more than 80% of the variance in gene expression. Males had higher expression of mitochondrial genes and mitochondrially targeted proteins (MTPs) involved in oxidative phosphorylation (OXPHOS), while females had elevated expression of non-OXPHOS MTPs, indicating strongly sex-dimorphic energy metabolism at the whole organism level. Comparison of reciprocal F1 hybrids allowed insights into the nature of mito-nuclear interactions, showing both mitochondrial effects on nuclear expression, and nuclear effects on mitochondrial expression. While based on a small set of crosses, sex-specific increases in mitochondrial expression with age were associated with longer life. Network analyses identified nuclear components of strong mito-nuclear interactions and found them to be sexually dimorphic. These results highlight the profound impact of mitochondria and mito-nuclear interactions on sex- and age-specific gene expression.

The evolution of olfactory sensitivity, preferences, and behavioral responses in Mexican cavefish is influenced by fish personality.

Animals are adapted to their natural habitats and lifestyles. Their brains perceive the external world via their sensory systems, compute information together with that of internal states and autonomous activity, and generate appropriate behavioral outputs. However, how do these processes evolve across evolution? Here, focusing on the sense of olfaction, we have studied the evolution in olfactory sensitivity, preferences, and behavioral responses to six different food-related amino acid odors in the two eco-morphs of the fish Astyanax mexicanus. To this end, we have developed a high-throughput behavioral setup and pipeline of quantitative and qualitative behavior analysis, and we have tested 489 six-week-old Astyanax larvae. The blind, dark-adapted morphs of the species showed markedly distinct basal swimming patterns and behavioral responses to odors, higher olfactory sensitivity, and a strong preference for alanine, as compared to their river-dwelling eyed conspecifics. In addition, we discovered that fish have an individual 'swimming personality', and that this personality influences their capability to respond efficiently to odors and find the source. Importantly, the personality traits that favored significant responses to odors were different in surface fish and cavefish. Moreover, the responses displayed by second-generation cave × surface F2 hybrids suggested that olfactory-driven behavior and olfactory sensitivity is a quantitative genetic trait. Our findings show that olfactory processing has rapidly evolved in cavefish at several levels: detection threshold, odor preference, and foraging behavior strategy. Cavefish is therefore an outstanding model to understand the genetic, molecular, and neurophysiological basis of sensory specialization in response to environmental change.

The evolution of olfactory sensitivity, preferences, and behavioral responses in Mexican cavefish is influenced by fish personality

Animals are adapted to their natural habitats and lifestyles. Their brains perceive the external world via their sensory systems, compute information together with that of internal states and autonomous activity, and generate appropriate behavioral outputs. However, how do these processes evolve across evolution? Here, focusing on the sense of olfaction, we have studied the evolution in olfactory sensitivity, preferences, and behavioral responses to six different food-related amino acid odors in the two eco-morphs of the fish Astyanax mexicanus. To this end, we have developed a high-throughput behavioral setup and pipeline of quantitative and qualitative behavior analysis, and we have tested 489 six-week-old Astyanax larvae. The blind, dark-adapted morphs of the species showed markedly distinct basal swimming patterns and behavioral responses to odors, higher olfactory sensitivity, and a strong preference for alanine, as compared to their river-dwelling eyed conspecifics. In addition, we discovered that fish have an individual ‘swimming personality’, and that this personality influences their capability to respond efficiently to odors and find the source. Importantly, the personality traits that favored significant responses to odors were different in surface fish and cavefish. Moreover, the responses displayed by second-generation cave × surface F2 hybrids suggested that olfactory-driven behavior and olfactory sensitivity is a quantitative genetic trait. Our findings show that olfactory processing has rapidly evolved in cavefish at several levels: detection threshold, odor preference, and foraging behavior strategy. Cavefish is therefore an outstanding model to understand the genetic, molecular, and neurophysiological basis of sensory specialization in response to environmental change.

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.

Genetic bias in repeated evolution of pigment loss in cave populations of the Asellus aquaticus species complex.

Similar phenotypes can evolve repeatedly under the same evolutionary pressures. A compelling example is the evolution of pigment loss and eye loss in cave-dwelling animals. While specific genomic regions or genes associated with these phenotypes have been identified in model species, it remains uncertain whether a bias towards particular genetic mechanisms exists. An isopod crustacean, Asellus aquaticus, is an ideal model organism to investigate this phenomenon. It inhabits surface freshwaters throughout Europe but has colonized groundwater on multiple independent occasions and evolved several cave populations with distinct ecomorphology. Previous studies have demonstrated that three different cave populations utilized common genetic regions, potentially the same genes, in the evolution of pigment and eye loss. Expanding on this, we conducted analysis on two additional cave populations, distinct either phylogenetically or biogeographically from those previously examined. We generated F2 hybrids from cave × surface crosses and tested phenotype-genotype associations, as well as conducted complementation tests by crossing individuals from different cave populations. Our findings revealed that pigment loss and orange eye pigment in additional cave populations were associated with the same genomic regions as observed in the three previously tested cave populations. Moreover, the lack of complementation across all cross combinations suggests that the same gene likely drives pigment loss. These results substantiate a genetic bias in the recurrent evolution of pigment loss in this model system. Future investigations should focus on the cause behind this bias, possibly arising from allele recruitment from ancestral surface populations' genetic variation or advantageous allele effects via pleiotropy.

Exploring nut quality traits in almond varieties: a comparative study of local and foreign cultivars and their F1 hybrid offsprings

Almonds are one of the most popular and widely consumed tree nuts in the world, prized for their taste, texture, and nutritional benefits. However, the quality and characteristics of almonds can vary significantly depending on the variety and growing conditions. In this context, a comparative study was conducted to explore the nut quality traits of almond local and foreign cultivars, as well as their F1 hybrid offspring resulting from crossbreeding. “Nut quality” is a dynamic concept changing based on consumer needs and perceptions that reflect sociocultural evolution. The aim of this study was to identify the most promising almond varieties and hybrids based on some nut quality traits including macro–micro elements and tocopherol contents. To accomplish this goal, samples were collected from local (Gulcan 2 and Nurlu) and foreign (Lauranne and Guara) almond cultivars, as well as F1 hybrid offspring resulting in two cross-breading (“Gulcan 2 × Lauranne” and “Guara × Nurlu”), and conducted a comprehensive analysis using high-performance liquid chromatography and atomic absorption spectroscopy. Our results showed that the nut quality traits of almonds can vary significantly among different cultivars and hybrids, with some varieties and hybrids exhibiting superior characteristics compared to others. These findings provide important insights into the potential for improving almond quality through crossbreeding and the development of new varieties with improved characteristics which can help inform breeding programs and improve the quality of almonds available in the market.

Heteroploid F1 hybrids generated from Coffea canephora × C. arabica interploidy crossing

Abstract Distant hybrids between two coffee species was considered promising for breeders to select novel genotypes highly resilient to changing global climate, despite pre- and or post-zygotic barriers. However, the different ploidy between C. arabica (2n=4x=44) and its diploid counterparts was another challenging barrier. The expected ploidy level for developed F1 hybrid was triploid. This study was aimed to identify ploidy level of F1 hybrids generated from Coffea canephora × C. arabica interploidy crossing. Ploidy determination was held using indirect methods, i.e. based on morphometric analysis of pollen and stomatal guard cells. Polar and equatorial diameter of 300 freshly collected pollen from each of six individuals of F1 hybrids were measured using ImageJ software. Stomatal frequency was measured as the number of guard cells on leaf area of 1 mm2. Pollen and stomatal guard cells of their diploid maternal and tetraploid paternal were also measured to be used as a standard for ploidy level determination. Generated datasets were immediately analysis statistically using t-Test procedure. The results shows that four of six F1 hybrid individuals had similar pollen size as well as stomatal density to diploid maternal. Meanwhile, another single individual was similar to tetraploid paternal. However, the rest of single individuals were similar to both of maternal and paternal. Based on those results, it could be inferred that there weres three different ploidy levels among F1 hybrid individuals, namely diploid, triploid, and tetraploid.

Genetic Identification of Medicinal Citrus Cultivar 'Local Juhong' Using Molecular Markers and Genomics.

The citrus cultivar 'Local Juhong', which has historically been used as a traditional Chinese medicinal material, originated in Yuanjiang County, Hunan Province.Its parental type and genetic background are indistinct as of yet. Morphological observation shows that 'Local Juhong' has a slight oblateness in fruit shape, a relatively smooth pericarp, a fine and slightly raised oil vacuole, and an inward concave at the blossom end. The tree form and fruit and leaf morphology of 'Local Juhong' are similar to those of 'Huangpi' sour orange. To reveal the genetic background of 'Local Juhong', 21 citrus accessions were evaluated using nuclear and chloroplast SSR markers and whole-genome SNP information. 'Local Juhong' was grouped with mandarins and sub-grouped with 'Miyagawa Wase' and 'Yanxi Wanlu' in a nuclear SSR analysis, which indicated that its pollen parent might be mandarins. It was closely clustered with orange and pummelo in the chloroplast SSR analysis. The genomic sequence similarity rate of 'Local Juhong' with mandarin and pummelo heterozygosity was 70.88%; the main part was the heterozygosity, except for the unknown (19.66%), mandarin (8.73%), and pummelo (3.9%) parts. Thus, 'Local Juhong' may be an F1 hybrid with pummelo as the female parent and mandarin as the male parent, sharing sisterhood with 'Huangpi' sour orange.

The effect of silkworms (Bombyx mori) chitosan on rumen fermentation, methanogenesis, and microbial population in vitro.

Ruminant enteric methane (CH4) is one of the largest sources of greenhouse gases that contribute to global warming. To minimize environmental harm caused by ruminants' CH4 production, natural substances can be used to suppress it. Chitosan from crustacean sources had been known to obstruct CH4 generation in the rumen. About 18% of silkworm pupae is chitin, but little is known about the impact of silkworm pupae chitosan on rumen methanogenesis. This study investigated the efficacy of the silkworm chitosan extraction method and its impact on rumen fermentation, methanogenesis, and microbial growth in vitro. This study employed a randomized complete block design featuring five treatments and four batches for rumen incubation as the blocking factor. In this study, five treatments were implemented: Control (CO) (basal diet with no added chitosan), basal diet with 6% chitosan from the Chinese Silkworm strain 804 (CHI804), basal diet with 6% chitosan from the PS 01 Hybrid Silkworm strain (CHIPS01), basal diet with 6% chitosan from the Hybrid F1 Japanese 102 × Chinese 202 races (CHIJC02), and basal diet with 6% commercial shrimp shell chitosan as the positive control (CHICOMM). The in vitro experiments assessed digestibility, pH, total gas generation, CH4 production, ammonia nitrogen (NH3-N), and short-chain fatty acid levels, along with microbial population. Data were analyzed using a general linear model followed by Duncan's test when applicable. A significant effect on dry matter digestibility (DMD), total gas production, CH4, NH3-N, and rumen microbial populations (Methanogens, Ruminoccocus albus, Ruminoccocus flavefaciens, Selonomonas ruminantium, Butyrivibrio fibrisolvens, Streptoccocus bovis, Prevotella spp., and Bacteroides spp.) was observed (p < 0.05). The extracted chitosan (CHIJC02) used in this study exhibited a similar quality to that of commercial chitosan (CHICOMM). CHI804 treatment could reduce gas production, NH3-N production, and B. fibrisolvens population significantly (p < 0.05), while CHIJC02 could reduce CH4 production, methanogen population, acetate (C2) production, and increase propionate (C3) production significantly (p < 0.05). CHIJC02 and CHICOMM treatments could also increase the population of R. flavefaciens, S. ruminantium, and Bacteroides spp. significantly (p < 0.05). Chitosan addition significantly (p < 0.05) reduced DMD but did not impact organic matter digestibility or pH. The extracted chitosan mimics commercial chitosan in physico-chemical properties. Chitosan derived from Japanese and Chinese F1 hybrid silkworm strains demonstrated superior capacity for inhibiting CH4 generation compared to commercial chitosan. The quality and effects on methanogenesis, rumen fermentation, and rumen microbial populations can differ depending on the origin of chitosan.

Unraveling genetic complexity: Identifying black gram (Vigna mungo L.) genotypes for rice fallow conditions

A study on generation mean analysis was conducted to determine suitable genotypes of black gram (Vigna mungo L.) for rice fallowconditions, considering various agronomic traits controlled by quantitative inheritance. The Hayman’s six-parameter model, utilizinga Random Block layout with two replications over six generations viz., P1, P2, F1, F2, BC1, and BC2 involving six parents viz., MDU 1, VBN(BG) 6, Mash-114 and ADT 3, PU 31 and CO 6 was followed. The filial generations derived from four crosses, along with their parentsinvolved in the hybridization, were evaluated at TRRI, Aduthurai, during the summer of 2019 under rice fallow conditions. The focus ofthe evaluation was on yield and its nine component traits, including plant height, branches per plant, 50% flowering, pods per cluster,pod number, 100 seed weight, and single plant yield. The study revealed a predominant influence of the duplicate dominant gene onthese yield attributes, indicating the complexity of the genetic basis. This complexity suggests that conventional selection methods may be hindered, making heterosis breeding or bulk method/recurrent selection more favorable for obtaining the desired gene combinations in genotypes suitable for rice fallow conditions.

Performance of Different Pumpkin (Cucurbita moschata) Hybrids for Growth, Yield and Quality under Prayagraj Agro-Climatic Condition

An experimental material comprised of 10 hybrid of pumpkin viz., SADABAHAR, PK-2507 F1hybrid, P6 F1 hybrid, P6 Gold F1hybrid, SS-76 F1 hybrid, SURAJ F1hybrid, SIPRA F1 hybrid, PRITVI F1hybrid, LHP-SINGHAM F1hybrid, SW-1001 F1hybrid.The investigation was carried out in a Randomized Block Design with three replications. Main Experiment Station of the Department of Vegetable Science at Sam Higginbottom University of Agriculture, Technology and Sciences Prayagraj (U.P) during the spring season. Present investigation reveuled that pumpkin hybrids viz, vine length cm (SW-1001 F1hybrid), no of braches (PK-2507 F1hybrid) performance best in term of growth. Two hybrids namely LHP-SINGHAM F1hybrid and SW-1001 F1hybrid performance best in term of yield. For the maximum number of fruit per plant and minimum node number for the first staminate flower anthesis was observed in the case of LHP-SINGHAM F1hybrid which is promoted to earliness and high yielding. Two hybrids namely P6 Gold F1hybrid TSS (°Brix), LHP-SINGHAM F1hybrid Vitamin c /100gm.

From heterosis to outbreeding depression: genotype-by-environment interaction shifts hybrid fitness in opposite directions.

In F1 hybrids, phenotypic values are expected to be near the parental means under additive effects or close to one parent under dominance. However, F1 traits can fall outside the parental range, and outbreeding depression occurs when inferior fitness is observed in hybrids. Another possible outcome is heterosis, a phenomenon that interspecific hybrids or intraspecific crossbred F1s exhibit improved fitness compared to both parental species or strains. As an application of heterosis, hybrids between channel catfish females and blue catfish males are superior in feed conversion efficiency, carcass yield, and harvestability. Over 20 years of hybrid catfish production in experimental settings and farming practices generated abundant phenotypic data, making it an ideal system to investigate heterosis. In this study, we characterized fitness in terms of growth and survival longitudinally, revealing environment-dependent heterosis. In ponds, hybrids outgrow both parents due to an extra rapid growth phase of 2-4 months in year 2. This bimodal growth pattern is unique to F1 hybrids in pond culture environments only. In sharp contrast, the same genetic types cultured in tanks display outbreeding depression, where hybrids perform poorly, while channel catfish demonstrate superiority in growth throughout development. Our findings represent the first example, known to the authors, of opposite fitness shifts in response to environmental changes in interspecific vertebrate hybrids, suggesting a broader fitness landscape for F1 hybrids. Future genomic studies based on this experiment will help understand genome-environment interaction in shaping the F1 progeny fitness in the scenario of environment-dependent heterosis and outbreeding depression.

Regulatory and evolutionary impact of DNA methylation in two songbird species and their naturally occurring F1 hybrids

BackgroundRegulation of transcription by DNA methylation in 5’-CpG-3’ context is a widespread mechanism allowing differential expression of genetically identical cells to persist throughout development. Consequently, differences in DNA methylation can reinforce variation in gene expression among cells, tissues, populations, and species. Despite a surge in studies on DNA methylation, we know little about the importance of DNA methylation in population differentiation and speciation. Here we investigate the regulatory and evolutionary impact of DNA methylation in five tissues of two Ficedula flycatcher species and their naturally occurring F1 hybrids.ResultsWe show that the density of CpG in the promoters of genes determines the strength of the association between DNA methylation and gene expression. The impact of DNA methylation on gene expression varies among tissues with the brain showing unique patterns. Differentially expressed genes between parental species are predicted by genetic and methylation differentiation in CpG-rich promoters. However, both these factors fail to predict hybrid misexpression suggesting that promoter mismethylation is not a main determinant of hybrid misexpression in Ficedula flycatchers. Using allele-specific methylation estimates in hybrids, we also determine the genome-wide contribution of cis- and trans effects in DNA methylation differentiation. These distinct mechanisms are roughly balanced in all tissues except the brain, where trans differences predominate.ConclusionsOverall, this study provides insight on the regulatory and evolutionary impact of DNA methylation in songbirds.

Influence of growth regulators on callus induction and plant regeneration from anthers of Tagetes spp.

Marigold (Tagetes spp.) belongs to family Asteraceae, native to Mexico, is one of the most important flower crop grown commercially in different parts of India. The application of haploid techniques as anther culture can considerably accelerate marigold breeding programmes by providing homozygous doubled haploid (DH) lines for F1 hybrid seed production. Therefore, the objective of the present investigation was to study the effect of growth regulators for in vitro regeneration in both African marigold and French marigold genotypes viz., Pusa Basanti Gainda and Pusa Arpita, respectively for haploid induction. Among the different treatments tested for callus induction, anthers cultured on MS medium supplemented with 1.0 mg/l BAP + 1.0 mg/l 2,4-D + 45 g/l sucrose significantly induced highest (38.74%) callus in the shortest period of time (16 days). Among two genotypes tested, embryogenic callus induction (27.70%) was significantly higher in Pusa Arpita over Pusa Basanti Gainda (23.37%). Among the different regeneration treatments, the highest adventitious shoot bud induction (13.32%), maximum (1.09) number of buds/callus in shortest duration (19.47 days) was observed in anther derived callus cultured on MS medium supplemented with 2.0 mg/l BAP + 0.5mg/l NAA + 30 g/l sucrose. Among two genotypes evaluated for shoot bud induction, maximum (3.81%) regeneration was recorded in Pusa Arpita over Pusa Basanti Gainda (2.90%). In French genotype, the whole regeneration process was completed in 30 days whereas in African genotype it took nearly 40 days. This rapid regeneration system from anthers is highly useful in inducing haploids and di-haploids in African and French marigold lines, respectively.