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Abstract Background Hybrids are expected to show greater phenotypic variation than their parental species, yet how hybrid phenotype expression varies with genetic distances in closely-related parental species remains surprisingly understudied. Here, we investigate pelage and morphometric trait variation in anthropogenic hybrids between four species of Brazilian Callithrix marmosets, a relatively recent primate radiation. Marmoset species are distinguishable by pelage phenotype and morphological specializations for eating tree exudates. In this work, we (1) describe qualitative phenotypic pelage differences between parental species and hybrids; (2) test whether significant quantitative differences exist between parental and hybrid morphometric phenotypes; and (3) determine which hybrid morphometic traits show heterosis, dysgenesis, trangression, or intermediacy relative to the parental trait. We investigated cranial and post-cranial morphometric traits, as most hybrid morphological studies focus on the former instead of the latter. Finally, we estimate mitogenomic distances between marmoset species from previously published data. Results Marmoset hybrid facial and overall body pelage variation reflected novel combinations of coloration and patterns present in parental species. In morphometric traits, C. jacchus and C. penicillata were the most similar, while C. aurita was the most distinct, and C. geoffroyi trait measures fell between these species. Only three traits in C. jacchus x C. penicillata hybrids showed heterosis. We observed heterosis and dysgenesis in several traits of C. penicillata x C. geoffroyi hybrids. Transgressive segregation was observed in hybrids of C. aurita and the other species. These hybrids were also C. aurita-like for a number of traits, including body length. Genetic distance was closest between C. jacchus and C. penicillata and farthest between C. aurita and the other species. Conclusion We attributed significant morphometric differences between marmoset species to variable levels of morphological specialization for exudivory in these species. Our results suggest that intermediate or parental species-like hybrid traits relative to the parental trait values are more likely in crosses between species with relatively lesser genetic distance. More extreme phenotypic variation is more likely in parental species with greater genetic distance, with transgressive traits appearing in hybrids of the most genetically distant parental species. We further suggest that fewer developmental disturbances can be expected in hybrids of more recently diverged parental species, and that future studies of hybrid phenotypic variation should investigate selective pressures on Callithrix cranial and post-cranial morphological traits.

The development of cayenne pepper varieties can be optimized by multiple crossings, transgressive segregant selection based on the selection index, and identification of potential anthocyanins. The study objectives were (1) to develop a transgressive segregation index, and (2) to select transgressive segregation cayenne peppers with high productivity and anthocyanins from F3 multiple cross-generation. The study conducted two experiments at the experimental field, Hasanuddin University, from November 2022 to November 2023. The first experiment implemented an augmented design with a randomized complete block design (RCBD) as an environmental design. The genotypes as treatment consisted of two types: 110 lines of cayenne pepper were not repeated, and the 4 older chili varieties as controls were repeated in each block. All genotypes were categorized and divided into five blocks. The second experiment was the validation of the first trial. There were 13 genotypes tested with RCBD design one factor and repeated three times. Based on the study, developing a semiobjective-based selection index with canopy width, fruit weight, and yield was an innovative and effective approach to selecting F3 transgressive segregants of cayenne pepper. High-yielding transgressive lines were identified as G3-2-7-3, G2.6.9-10, G5-12-1-8, and G4.5.2-12. The G3-2-7-3 line was suggested due to its high yield potential and anthocyanin content. However, the anthocyanin content must be examined more deeply, such as using an omics approach. Nevertheless, these lines are still recommended to be continued in yield testing or crossing to produce hybrid lines that have high yield potential and anthocyanin content. [ABSTRACT FROM AUTHOR]

The primary causes of low sesame production are a lack of high-yielding varieties, an inability to adjust to environmental challenges, and a poor response to enhanced crop management. The potential for improving sesame has been investigated using a variety of breeding approaches, including mutation and recombination breeding; however, these methods have only produced a minor increase in productivity. Recombination and mutant breeding have recently been proposed as novel, cutting-edge approaches to overcome the limitations of conventional breeding practices. This study was conducted to assess the recurrent mutagenesis efficacy of sesame crosses, followed by the isolation and evaluation of superior breeding lines that could be released as varieties in the future. In the F4M4 generation, the populations were grown in a randomized block design (RBD), and the efficacy of recurrent mutagenesis was assessed in terms of variability parameters such as the mean, standard deviation, and coefficient of variation. During the F5M5 generation, the materials were grown in three separate trials in Compact Family Block Design to evaluate the between-family and within-family variations, followed by the isolation of improved breeding lines based on per se performance. The improved breeding lines were further advanced to the F6M6 generation for evaluation in three separate trials in an RBD. In the F6M6 generation, ANOVA, correlation, regression, path coefficient, and Mahalanobis’s D 2 analysis were computed, followed by the construction of selection indices to select superior lines. The results showed the importance of three or four EMS treatment cycles for sesame improvement in the F4M4 generation. Twenty of the top lines based on per se performance (with a selection intensity of 27%) from each category in the F5M5 generation were carried forward to the F6M6 generation. In the F6M6 generation, the top six breeding lines (with a selection intensity of 30%) from each category, for a total of 18 breeding lines, were chosen based on these index scores. These high-yielding micromutant lines could be subsequently released as varieties through multiplication trials with standard checks. After a thorough evaluation, these lines have the potential to replace the current varieties and increase production, productivity, and adoption of sesame in India.

Barley with high grain β-glucan content is valuable for functional foods. The identification of loci for high β-glucan content is, thus, of great importance for barley breeding. Segregation mapping for the content in β-glucan and other barley grain components (starch, protein, lipid, ash, phosphorous, calcium, sodium) was performed using the progeny of the cross between Glacier AC38, a mutant with high amylose, and CDC Fibar, a high β-glucan waxy cultivar. The offspring of this cross showed transgressive segregation for β-glucan content. Linkage analysis based on single-nucleotide polymorphism (SNP) molecular markers was used for the genotyping of the parents and recombinant inbred lines (RILs). Two Quantitative Trait Loci (QTL) for β-glucan content and several QTL for other grain components were found. The former ones, located on chromosomes 1H and 7H, explained 27.9% and 27.4% of the phenotypic variance, respectively. Glacier AC38 provided the allele for high β-glucan content at the QTL on chromosome 1H, whereas CDC Fibar contributed the allele at the QTL on chromosome 7H. Their recombination resulted in a novel haplotype with higher β-glucan content, up to 18.4%. Candidate genes are proposed for these two QTL: HvCslF9, involved in β-glucan biosynthesis, for the QTL on chromosome 1H; Horvu_PLANET_7H01G069300, a gene encoding an ATP-Binding Cassette (ABC) transporter, for the QTL on chromosome 7H. [ABSTRACT FROM AUTHOR]

The presence of epistasis in complex traits can be significant and affect the selection of segregating populations undesirably. The purpose of this study was to determine the epistatic genetic components that influence root and shoot traits of common bean and identify their effect on the performance of segregating populations. The field experiment consisted of 49 treatments (backcross progenies, parents and segregating populations in the F2 and F3 generations). The cross P1-BAF53 (Andean) × P2-IPR 88 Uirapuru (Mesoamerican) as reference. Six traits were taken into consideration: root distribution (%), first pod length (cm), number of grains (plot), plant height (cm), reproductive cycle (days) and number of basal branches (plot). For root distribution, first pod length and number of grains, the additive and additive × additive components were significant. On the contrary, for plant height, reproductive cycle and number of basal branches, no interaction component was observed. These results can be explained by the magnitude of variance determined for these traits. The additive × additive epistasis had a negative influence on the mean performance of segregating progenies. Contrariwise, transgressive segregation effects on plant height were observed as a function of genetic dominance deviation. Thus, additive × additive epistasis can hamper the success of a breeding program, for being associated with low-variability traits. This fact may be related with the number of crosses and/or the choice of genetically more distant parents for the program, and possibly with the presence of linked genes. [ABSTRACT FROM AUTHOR]

The development of cayenne pepper varieties can be optimized by multiple crossings, transgressive segregant selection based on the selection index, and identification of potential anthocyanins. The study objectives were (1) to develop a transgressive segregation index, and (2) to select transgressive segregation cayenne peppers with high productivity and anthocyanins from F3 multiple cross-generation. The study conducted two experiments at the experimental field, Hasanuddin University, from November 2022 to November 2023. The first experiment implemented an augmented design with a randomized complete block design (RCBD) as an environmental design. The genotypes as treatment consisted of two types: 110 lines of cayenne pepper were not repeated, and the 4 older chili varieties as controls were repeated in each block. All genotypes were categorized and divided into five blocks. The second experiment was the validation of the first trial. There were 13 genotypes tested with RCBD design one factor and repeated three times. Based on the study, developing a semi-objective-based selection index with canopy width, fruit weight, and yield was an innovative and effective approach to selecting F3 transgressive segregants of cayenne pepper. High-yielding transgressive lines were identified as G3-2-7-3, G2.6.9–10, G5-12–1-8, and G4.5.2–12. The G3-2-7-3 line was suggested due to its high yield potential and anthocyanin content. However, the anthocyanin content must be examined more deeply, such as using an omics approach. Nevertheless, these lines are still recommended to be continued in yield testing or crossing to produce hybrid lines that have high yield potential and anthocyanin content.

Introduction Cantaloupes, are a group of Cucumis melo cultivars, that have round, fragrant fruits with netted skin. Our country, is one of the top five producers of cantaloupe, and melon in the world. Its original origin, is still debated, but one of the important centers of its diversity, is Iran. Although, native cultivars, such as, Saveh cantaloupe, Samsoori, Rish Baba, and various types of Tiles, are often of good quality, and taste, but they are sensitive to a variety of fungal and viral diseases and as a result, their yield is low. On the other hand, every year new cultivars and hybrids, are introduced by seed companies, which are welcomed by farmers, due to, their better agronomic characteristics, and resistance to a wider range of diseases. Continuation of this process, in addition to severe genetic erosion of native cultivars, and populations, and even the complete elimination of some of them, will have consequences such as, dependence of production on foreign companies, annual departure of currency from the country, and non-exploitation of the country's genetic resources. Therefore, it seemed that by creating a diverse population resulting from the crossing of superior native cultivars with cultivars of commercially resistant hybrid to diseases, and then, successive selections, new cultivars, with desirable traits of both parents, could be achieved. Thus, in this study, heritability, minimum and maximum mean values of parents, and F1 and F2 generations, aggressive segregation, and relative frequency of qualitative traits, in F2 generation, and selection of the best genotypes, in two dispersing NGF2 populations, were investigated. Materials and Methods Parental cross, was performed in the spring of 2017, between Samsoori cantaloupe cultivar (round, striped fruit, cream skin color, completely reticulate, green flesh, very early ripening fruit, poor transportability and durability, free pollinator and high homogeneity) as the selected native paternal parent, and commercial cultivar from Gallia group, that called Cory and as maternal parent (round fruit, completely reticulate, no striped skin, yellow to cream skin color, high transportability and durability, green and very sweet flesh, high resistance to various plant diseases and viral diseases) and produced by Seminis Company. The first-generation seeds, obtained from parental crosses, were planted in the greenhouse in the fall of 2017, and were self-sown. In the spring of 1397, 1000 seeds of F2 generation, along with parent seeds, and their first generation, were planted in a seedling tray, in the greenhouses of the Faculty of Agricultural Technology (Aborihan) of Tehran University, and transplanted to the ground, in the rental research production farm, located, in Filistan village-Golzar sector-Pakdasht. Controlled pollination, (isolation of male flowers, and manual inoculation) was performed, for all second-generation plants. Selection for subsequent generations, was done by pedigree method, all plants in F2 generation, were evaluated, and selected. Morphological traits, such as, plant form and phenological traits, such as, day to fruit harvest, were evaluated, and recorded. Plant health, was assessed against common and important fungal, viral and mites, under normal field conditions by scoring the severity of infections in four categories. Fruit quality traits were measured based on nominal, sequential and interval scales and quantitative fruit traits were also measured. Tables of minimum and maximum values, variances, general heritability, transgressive segregation, etc for quantitative traits, also relative frequency percentages and observed genetic ratios for quantitative traits, were calculated. Results and Discussion The results showed that all quantitative traits in the F2 population had a general heritability above 90%. The mean of all quantitative traits except soluble solids and fruit flesh thickness in F1 population was lower than the parental average. In F2 population, for all quantitative traits, positive transgressive segregation was observed, compared to, the superior parent, and negative transgressive segregation was observed, compared to, the less valuable parent. In the F2 population, nearly 80% of the genotypes, were completely reticulate, and 20% had less or no netting, on the fruit skin. These results were almost consistent with genetic ratios of 3.1. Also, 35% of F2 population genotypes, were striped and more than 80% of them had yellowish skin color and green flesh color. Due to, the fact that, selection based on traits with high heritability, will be more reliable, and successful in early generations, so, it is better, to select the best genotypes, in this population, based on fruit weight, soluble solids, and early maturity, respectively. ConclusionIn the F2 population, positive transgressive segregation was evident for all quantitative traits, favoring the superior parent, while negative segregation was observed for the less valuable parent. Traits exhibiting high heritability showcased a pronounced influence of genetic variance over environmental variance. Consequently, selecting cultivars based on these traits in early generations is expected to yield more reliable and successful outcomes. Therefore, it is better, to selection, the best genotypes in the early generations, in the F2 population, based on fruit weight, (with high genetic efficiency), soluble solids, day to fruit ripening, and with the pedigree management, of the populations, it is finally, possible to achieve lines, that have the desirable traits, of both parental cultivars. The resulting lines, can be used to produce, new hybrids, or provided, to the farmer, as a single cultivar.

Haploid inducers are key components of doubled haploid (DH) technology in maize. Robust agronomic performance and better haploid induction ability of inducers are persistently sought through genetic improvement. We herein developed C1-I inducers enabling large-scale in vivo haploid induction of inducers and discovered superior inducers fromthe DH progenies. The haploid induction rate (HIR) of C1-I inducers ranged between 5.8% and 12.0%. Overall, the success rate of DH production was 13% on average across the 23 different inducer crosses. The anthesis-silking interval and days to flowering of inducer F1s are significantly correlated with the success rate of DH production (r = -0.48 and 0.47, respectively). Transgressive segregants in DH inducers (DHIs) were found for the traits (days to flowering, HIR, plant height, and total primary branch length). Moreover, the best HIR in DHIs exceeded 23%. Parental genome contributions to DHI progenies ranged between 0.40 and 0.55, respectively, in 25 and 75 percentage quantiles, and the mean and median were 0.48. The allele frequency of the four traits from inducer parents to DHI progenies did not correspond with the phenotypic difference between superior and inferior individuals in the DH populations by genome-wide Fst analysis. This study demonstrated that the recombinant DHIs can be accessed on a large scale and used as materials to facilitate the genetic improvement of maternal haploid inducers by in vivo DH technology. [ABSTRACT FROM AUTHOR]

Introduction. Segregated populations can show the fluctuating performance of one generation to another. This can sometimes confuse plant breeders in interpreting the observed phenomena and determining the selection methods that need to be chosen. Objective. To analyze the performance and yield components of several tomato (Solanum lycopersicum) populations using the pedigree method in lowland environments, Bogor, West Java, Indonesia. Materials and methods. This study was conducted in December 2018–April 2019, at the Experimental Garden of Bogor Agricultural University, Tajur II (207 meters above sea level), Bogor, West Java, Indonesia. Four generations generated from 99D×Tora were used in the study, i.e. 200 plants of F2 generation and 100 plants of each of F3, F5, and F6 generations, respectively. Results. The results showed that the population variance in terms of yield and yield components and heritability were lower in the later generation compared with the earlier generation. Increase in the mean value was observed in F3 generation, but decreased in F5 and F6 generations in all observed characters. It could be caused by fixation as the result of the elimination of epistasis genes that played a role in the environmental stress. Conclusion. Pedigree selection at early generation was not suitable in the lowland. It is suggested to evaluate bulk or single seed descent methods, as those methods were able to maintain population variance up to later generations.

The genetic base in Upland cotton (Gossypium hirsutum L.) is narrow. Repeated random mating through generations during germplasm development may be an appealing approach to introgress desirable genes from exotic germplasm into Upland cotton. A random mating population, MDRM, was developed to provide a source of germplasm with introgression of novel alleles from other tetraploid species. This population was derived from 48 crosses between four Upland cotton lines/cultivars (MD15, MD52ne, and TAM98D-99ne and FiberMax832) as female parents and twelve exotic germplasm lines as male parents. The male parents include six lines derived from multiple crosses between G. hirsutum and G. barbadense L. and another six lines derived from multiple crosses among five Gossypium tetraploid species. After five generations of random mating followed by six generations of self-pollination, the bulk of RM5F7 population was produced, which further led to the development of recombinant inbred lines (RILs) from seed increase of single plants in the bulk. The bulk of RM5F7 and its 276 RILs were evaluated along with 134 RM0F7 RILs (0 generation of random mating) and 142 RM1F7 RILs (1 generation of random mating) and the parents at College Station, TX, Las Cruces, NM, and Stoneville, MS from 2016 to 2022. The bulk of RM5F7 has superior fiber quality with acceptable yield as compared with parents. Transgressive segregation was observed in RM5F7 RILs for both lint yield and fiber quality. Unfavorable associations between yield and fiber properties of length, strength, and uniformity in RM5F7 were reduced compared with RM0F7 or RM1F7. Therefore, MDRM provides a new breeding stock for cotton breeders to develop germplasm lines with desirable combinations between lint yield and fiber quality and unique combinations of alleles from exotic parents. [ABSTRACT FROM AUTHOR]

Hybridization can rapidly generate novel genetic variation, which can promote ecological speciation by creating novel adaptive phenotypes. However, it remains unclear how hybridization, creating novel mating phenotypes (e.g. mating season, genitalia shapes, sexual displays, mate preferences), affects speciation especially when the phenotypes do not confer adaptive advantages. Here, based on individual-based evolutionary simulations, we propose that transgressive segregation of mating traits can drive incipient hybrid speciation. Simulations demonstrated that incipient hybrid speciation occurred most frequently when the hybrid population received moderate continued immigration from parental lineages causing recurrent episodes of hybridization. Recurrent hybridization constantly generated genetic variation, which promoted the rapid stochastic evolution of mating phenotypes in a hybrid population. The stochastic evolution continued until a novel mating phenotype came to dominate the hybrid population, which reproductively isolates the hybrid population from parental lineages. However, too frequent hybridization rather hindered the evolution of reproductive isolation by inflating the variation of mating phenotypes to produce phenotypes allowing mating with parental lineages. Simulations also revealed conditions for the long-term persistence of hybrid species after their incipient emergence. Our results suggest that recurrent transgressive segregation of mating phenotypes can offer a plausible explanation for hybrid speciation and radiations that involved little adaptive ecological divergence. [ABSTRACT FROM AUTHOR]

The most important commercial feature in popcorn (Zea mays L.) is the expansion of the starch contained in the endosperm; however, little has been studied about the underlying genetic basis of this quantitative trait, for which the development of segregating populations is required. The first step is the selection of the most appropriate contrasting parents for popping capacity to create these populations. The objectives of this study were, 1) to analyze the popping patterns of F2 populations derived from crosses between popcorn × nonpopcorn inbred lines to identify the most divergent cross for future molecular analysis in search of alleles-related to popping capacity, and 2) to estimate the number of genes responsible for popping expansion volume based on the tails of segregation. Seven biparental crosses of popcorn × non-popcorn were performed to obtain F2 populations, and those were phenotyped for popping expansion volume. Phenotypes were analyzed by the H test, Lilliefors normality-test, Fisher’s coefficient of skewness, and kurtosis level. The number of genes estimation was made with X2and (1/4)n tests. The popping patterns indicated that popcorn × flint corn was the most divergent cross, with the most symmetrical distribution, and therefore, the best suitable population to be used for molecular analysis. Results indicated the existence of three to five major genes related to popping expansion volume. Transgressive segregation was present in all populations, showing individuals whit a popping expansion volume higher or lower than the parental ones, suggesting that non-popcorn lines contain variation for alleles that promote popping. [ABSTRACT FROM AUTHOR]

Drought is one of the most important environmental factors affecting plant growth. The double haploid method is one of the most common breeding methods in wheat. Using old cultivars in cross-breeding programs can be effective for restoring genes lost during evolution. In this study, in order to evaluate the genetic diversity and to select the drought-tolerant introgression wheat lines, 151 double haploid (DH) lines (derived from cross of old and modern cultivars) were evaluated under two moisture conditions (non-stress and drought-stress) in field. Considerable genetic variation was observed among DH lines for most of the traits indicating that selection for these traits can be effective to develop lines with higher performance or for specific purposes. The effect of drought stress was significant for most of the traits. For example, drought stress reduced grain yield by 40%. Comparison of old and new parent genotypes showed that the new parent was earlier in maturity, dwarf and had higher grain yield, yield components and harvest index. Transgressive segregation was observed for most of the traits indicating the possibility of selection for superior lines. In both moisture condition, plant height had the highest narrow sense heritability (46%) and leaf relative water content had the lowest one (12%). Grain yield had negative correlation with day to flowering indicating that selection for earliness can improve drought tolerance. According to the results of tolerance indices and biplot of principle component analysis, superior lines were identified. For example superior lines for grain yield, early flowering and higher harvest index were recognized for future studies.

A collection of 30 melon introgression lines (ILs) was developed from the wild accession Ames 24297 (TRI) into 'Piel de Sapo' (PS) genetic background. Each IL carried an average of 1.4 introgressions from TRI, and the introgressions represented 91.4% of the TRI genome. Twenty-two ILs, representing 75% of the TRI genome, were evaluated in greenhouse (Algarrobo and Meliana) and field (Alcàsser) trials, mainly to study traits related to domestication syndrome such as fruit weight (FW) and flesh content (FFP), as well as other fruit quality traits as fruit shape (FS), flesh firmness (FF), soluble solid concentration (SSC), rind color and abscission layer. The IL collection showed an impressive variation in size-related traits, with FW ranging from 800 to 4100 g, reflecting the strong effect of the wild genome on these traits. Most of the ILs produced smaller fruits compared with PS; however, unexpectedly, the IL TRI05-2 produced bigger fruits, likely due to new epistatic interacions with the PS genetic background. In contrast, the genotypic effect for FS was smaller, and few QTLs with notable effects were detected. Interestingly, variability was also observed for FFP, FF and SSC, rind color and abscission layer formation. Genes in these introgressions are candidates for having been involved in melon domestication and diversification as well. These results confirm that the TRI IL collection is a very powerful tool for mapping traits of agronomic interest in melon, allowing the confirmation of previously reported QTLs and the identification of new ones to better understand the domestication process of this crop. [ABSTRACT FROM AUTHOR]

Hybridization can promote phenotypic variation and often produces trait combinations distinct from the parental species. This increase in available variation can lead to the manifestation of functional novelty when new phenotypes bear adaptive value under the environmental conditions in which they occur. Although the role of hybridization as a driver of variation and novelty in traits linked to fitness is well recognized, it remains largely unknown whether hybridization can fuel behavioral novelty by promoting phenotypic variation in brain morphology and/or cognitive traits. To address this question, we investigated the effect of hybridization on brain anatomy, learning ability, and cognitive flexibility in first‐ and second‐generation hybrids of two closely related fish species (Poecilia reticulata and Poecilia wingei). Overall, we found that F1 and F2 hybrids showed intermediate brain morphology and cognitive traits compared to parental groups. Moreover, as phenotypic dispersion and transgression were low for both brain and cognitive traits, we suggest that hybridization is not a strong driver of brain anatomical and cognitive diversification in these Poeciliidae. To determine the generality of this conclusion, hybridization experiments with cognitive tests need to be repeated in other families. [ABSTRACT FROM AUTHOR]

Hybridization is an important mechanism of evolution. While hybrids often express inferior traits and are selected against, hybridization can promote phenotypic variation and produce trait combinations distinct from the parentals, generating novel adaptive potential. Among other traits, hybridization can impact behavior and cognition and may reinforce species boundaries when hybrids show decreased cognitive abilities. However, the hypothesized role of hybridization in the diversification of cognitive phenotypes remains enigmatic. To test this idea, we compare the performance of female guppies (Poecilia reticulata), Endler's guppies (Poecilia wingei), and their experimental hybrids in color association and reversal learning. In addition, we introduce a new approach to compare multidimensional cognitive phenotypes. We found that hybrids showed intermediate learning abilities in both tasks compared with the parentals. Moreover, hybrids had slightly higher phenotypic dispersion, new trait combinations occurred in some hybrid individuals, and the mean phenotype of one hybrid group deviated away from the axis of variation of the parentals. Our method should hence be useful in further exploring how hybridization and other evolutionary processes impact behavioral and cognitive traits. Our results suggest that hybridization may promote cognitive variation and generate new trait combinations, even when learning performance at the group level is intermediate between parentals. [ABSTRACT FROM AUTHOR]

Drought is one of the most important environmental factors affecting plant growth. The double haploid method is one of the most common breeding methods in wheat. Using old cultivars in cross-breeding programs can be effective for restoring genes lost during evolution. In this study, in order to evaluate the genetic diversity and to select the droughttolerant introgression wheat lines, 151 double haploid (DH) lines (derived from cross of old and modern cultivars) were evaluated under two moisture conditions (non-stress and drought-stress) in field. Considerable genetic variation was observed among DH lines for most of the traits indicating that selection for these traits can be effective to develop lines with higher performance or for specific purposes. The effect of drought stress was significant for most of the traits. For example, drought stress reduced grain yield by 40%. Comparison of old and new parent genotypes showed that the new parent was earlier in maturity, dwarf and had higher grain yield, yield components and harvest index. Transgressive segregation was observed for most of the traits indicating the possibility of selection for superior lines. In both moisture condition, plant height had the highest narrow sense heritability (46%) and leaf relative water content had the lowest one (12%). Grain yield had negative correlation with day to flowering indicating that selection for earliness can improve drought tolerance. According to the results of tolerance indices and biplot of principle component analysis, superior lines were identified. For example superior lines for grain yield, early flowering and higher harvest index were recognized for future studies. [ABSTRACT FROM AUTHOR]

Handling of segregating populations arising from a large number of crosses in Plant Breeding is a challenging and vital task. Identification of potential of the particular cross will aid in the selection of superior segregants. In the present study, four crosses derived from parents contrasting for seed yield and most of its attributing traits was assessed by comparing the 11 quantitative traits, mean values, phenotypic coefficient of variation, standardized range and frequency of transgressive segregants in F2 and F3 generations in cowpea. Based on per se mean value , variances, standardized range and frequency of transgressive segregants in F2 and F3 generations derived from four crosses, PL-2 × NBC-39 was predicted to have better breeding potential followed by PL-5 × EC-402104 in terms of chances of isolating desirable recombinants in advanced generations. Increasing trend in mean values, variances, and frequency of transgressive segregants for most of the traits from F2 to F3 generations derived PL-2 × NBC-39 and PL-5 × EC-402104 supported the conclusion, although a decreasing trend was observed for standardized range in all four crosses. Identification of 10 best F3 plants in PL-2 × NBC-39 indicated the utility of mean values, variances, standardized range and frequency of transgressive segregants in predicting the performance of a cross to maximize the frequency of superior segregants in advanced generations.

The wild Cicer species is well-known for having climate-resilient and productivity-enhancing traits of interest. Therefore, wide hybridization could be used as a realistic strategy for introgressing prospective traits from wild species into the cultivated gene pool. The present study was, thus, undertaken to evaluate F7 chickpea interspecific derivatives derived fromCicer reticulatum Ladiz. and C. echinospermum P. H. Davis wild annual Cicer species. As a result, a set of six interspecific crosses were advanced using the single seed descent (SSD) method of breeding. The F7 generation of these crosses was assessed in two diverse agro-ecological regions of India. The data revealed a wide range of variation with respect to seed yield and its important component traits, which resulted in the identification of the most promising derivatives carrying desirable characters as indicated by range, mean, and coefficient of variation. Further, fruitful heterosis was also estimated as promising selection criteria for identifying superior lines for earliness and high seed yield, including resistance against prevailing stresses (ascochyta blight, botrytis gray mold, dry root rot, and fusarium wilt). The superior derivatives carrying putative characters could be recommended for further breeding and selection of genetic materials for developing suitable genotypes. [ABSTRACT FROM AUTHOR]

The wild Cicer species is well-known for having climate-resilient and productivity-enhancing traits of interest. Therefore, wide hybridization could be used as a realistic strategy for introgressing prospective traits from wild species into the cultivated gene pool. The present study was, thus, undertaken to evaluate F7 chickpea interspecific derivatives derived from Cicer reticulatum Ladiz. and C. echinospermum P. H. Davis wild annual Cicer species. As a result, a set of six interspecific crosses were advanced using the single seed descent (SSD) method of breeding. The F7 generation of these crosses was assessed in two diverse agro-ecological regions of India. The data revealed a wide range of variation with respect to seed yield and its important component traits, which resulted in the identification of the most promising derivatives carrying desirable characters as indicated by range, mean, and coefficient of variation. Further, fruitful heterosis was also estimated as promising selection criteria for identifying superior lines for earliness and high seed yield, including resistance against prevailing stresses (ascochyta blight, botrytis gray mold, dry root rot, and fusarium wilt). The superior derivatives carrying putative characters could be recommended for further breeding and selection of genetic materials for developing suitable genotypes.

Behaviours are challenging to describe. Here, we apply k -mer analysis to characterize complex courtship behaviours at four hierarchical levels: elements, displays, bouts and repertoires, on two species of hummingbirds and their hybrids. During courtship, male rufous hummingbirds, Selasphorus rufus , perform three types of displays: shuttles (S), half pendulums (H) and rufous dives (R), while Allen's hummingbirds, Selasphorus sasin , perform four displays: S, H, Allen's dives (A) and the pendulum (P). Here we explore the behavioural sequences expressed by their hybrids, on a sample of displays from 35 Allen's hummingbirds and 46 rufous hummingbirds sampled far from their hybrid zone, compared against 306 wild male birds from a hybrid zone in Oregon and California, U.S.A. Among Allen's hummingbirds, hybrids and rufous hummingbirds, there was almost no variation in the kinematic elements that comprised displays. By contrast, the displays themselves, display sequences and repertoires varied substantially among these three groups. Some hybrids performed transgressive display variants in which kinematic elements of typical displays were missing or duplicated. This transgressive segregation implies the displays are under oligogenic control. We analysed display sequences using k -mer analysis, in which we binned display sequences into 3-mers (sequences of three). Typical 3-mers for Allen's hummingbirds included sequences PPP, PPA and SHP while typical 3-mers for rufous hummingbirds included SHR and RRR. The most defining characteristic of certain hybrids was their sequence variability: the display repertoire of some hybrids encompassed the repertoire of both parent species (e.g. performed both PPA and RRR) as well as 3-mer sequences never observed in either parent such as PRA. Such high within-individual variability in hybrid phenotype differs from how modular morphological traits (such as flowers, feathers or hair) are expressed in hybrids. This within-individual variability may be unique to behaviour. • We analysed courtship sequences from 306 hummingbird hybrids in a hybrid zone. • Some individuals performed transgressive displays with extra display elements. • Some hybrid individuals were highly variable in their courtship display sequences. [ABSTRACT FROM AUTHOR]

Paspalum dilatatum Poir. is a perennial apomictic and pentaploid South American grass and a very valued forage crop. The species has been available commercially in several parts of the world; however, its low seed production, apomictic reproduction and ergot susceptibility are important limitations for its adoption and breeding. The Dilatata complex includes five sexual tetraploid mostly selfing species, very closely related to P. dilatatum, which can be hybridized in different combinations. To explore the productive potential of breeding this species group as a sexual selfing tetraploid by combining germplasm from different tetraploid sources, a cross was made between Paspalum flavescens and Paspalum plurinerve which showed high productivity and resistance to ergot. The F1 was compared to the parents and 20 F3 families to evaluate the presence of heterosis, and estimate the additive genetic variance and the degree of transgressive segregation for morphological and productive traits. The F1 showed heterosis for dry matter and the number of fertile tillers, while the F3 showed transgressive segregation in more than 30% of the families for most traits. These results show that hybridization at the tetraploid level can generate vigorous and productive recombinants with a high potential to produce promising transgressive segregants. This breeding strategy appears highly promising, supporting further research on the potential of interspecific hybridization in this group. [ABSTRACT FROM AUTHOR]

Under incomplete reproductive isolation, secondary contact of diverged allopatric lineages may lead to the formation of hybrid zones that allow to study recombinants over several generations as excellent systems of genomic interactions resulting from the evolutionary forces acting on certain genes and phenotypes. Hybrid phenotypes may either exhibit intermediacy or, alternatively, transgressive traits, which exceed the extremes of their parents due to epistasis and segregation of complementary alleles. While transgressive morphotypes have been examined in fish, reptiles, birds, and mammals, studies in amphibians are rare. Here, we associate microsatellite‐based genotypes with morphometrics‐based morphotypes of two tree frog species of the Hyla arborea group, sampled across a hybrid zone in Poland, to understand whether the genetically differentiated parental species also differ in morphology between each other and their hybrids and whether secondary contact leads to the evolution of intermediate or transgressive morphotypes. Using univariate approaches, explorative multivariate methods (principal component analyses) as well as techniques with prior grouping (discriminant function analyses), we find that morphotypes of both parental species and hybrids differ from each other. Importantly, hybrid morphotypes are neither intermediate nor transgressive but found to be more similar to H. orientalis than to H. arborea. [ABSTRACT FROM AUTHOR]

Understanding the origins of phenotypic diversity among closely related species remains an important largely unsolved question in evolutionary biology. With over 800 species, Lake Malawi haplochromine cichlid fishes are a prominent example of extremely fast evolution of diversity including variation in colouration. Previously, a single major effect gene, agrp2 (asip2b), has been linked to evolutionary losses and gains of horizontal stripe patterns in cichlids, but it remains unknown what causes more fine‐scale variation in the number and continuity of the stripes. Also, the genetic basis of the most common colour pattern in African cichlids, vertical bars, and potential interactions between the two colour patterns remain unknown. Based on a hybrid cross of the horizontally striped Lake Malawi cichlid Pseudotropheus cyaneorhabdos and the vertically barred species Chindongo demasoni we investigated the genetic basis of both colour patterns. The distribution of phenotypes in the F2 generation of the cross indicates that horizontal stripes and vertical bars are independently inherited patterns that are caused by two sets of genetic modules. While horizontal stripes are largely controlled by few major effect loci, vertical bars are a highly polygenic trait. Horizontal stripes show substantial variation in the F2 generation that, interestingly, resemble naturally occurring phenotypes found in other Lake Malawi cichlid species. Quantitative trait loci (QTL) mapping of this cross reveals known (agrp2) and unknown loci underlying horizontal stripe patterns. These findings provide novel insights into the incremental fine‐tuning of an adaptive trait that diversified through the evolution of additional modifier loci. [ABSTRACT FROM AUTHOR]

Extreme F2 phenotypes known as transgressive segregants can cause increased or decreased fitness in hybrids beyond the ranges seen in parental populations. Despite the usefulness of transgression for plant and animal breeding and its potential role in hybrid speciation, the genetic mechanisms and predictors of transgressive segregation remain largely untested. We generated seven hybrid crosses between five widely divergent Saccharomyces yeast species and measured the fitness of the parents and their viable F1 and F2 hybrids in seven stressful environments. We found that on average 16.6% of all replicate F2 hybrids had higher fitness than both parents. Against our predictions, transgression frequency was not a function of parental genetic and phenotypic distances across test environments. Within environments, some relationships were significant, but not in the predicted direction; for example, genetic distance was negatively related to transgression in ethanol and hydrogen peroxide. Significant effects of hybrid cross, test environment, and cross × environment interactions suggest that the amount of transgression produced in a hybrid cross is highly context specific and that outcomes of hybridization differ even among crosses made from the same two parents. If the goal is to reliably predict hybrid fitness and forecast the evolutionary potential of admixed populations, we need more efforts to identify patterns beyond the idiosyncrasies caused by specific genomic or environmental contexts. [ABSTRACT FROM AUTHOR]

This novel transgressive segregation has 125.8 kernels/spike, 10 spikes/plant and 61.98 g for grain yield/plant, however, it has 3.31 kernels/spikelet and 49.27 g for 1000- kernel weight. High positive and significant correlation coefficients occurred between number of kernels/spike and number of spike-lets/spike and between number of kernels/spike and number of kernels/spikelet. The F[sub 3] population had a maximum 38 spikelets/spike, 194.5 kernels/spike, 6.1 kernels/spikelet, 19.0 fertile spikes/plant, 64.72 g for 1000-kernel weight and 115.11 g for grain yield/plant. High positive and significant correlation coefficients occurred between number of kernels/spike and number of spikelets/spike (0.40**) and between number of kernels/spike and number of kernels/spikelet (0.80**). [Extracted from the article]

Transgressive segregation produces hybrid progeny phenotypes that exceed the parental phenotypes. Unlike heterosis, extreme phenotypes caused by transgressive segregation are heritably stable. We examined transgressive phenotypes of flowering time in rice, and revealed transgressive segregation in F2 populations derived from a cross between parents with similar (proximal) days to heading (DTH). The DTH phenotypes of the A58 × Kitaake F2 progenies were frequently more extreme than those of either parent. These transgressive phenotypes were maintained in the F3 and F4 populations. Both A58 and Kitaake are japonica rice cultivars adapted to Hokkaido, Japan, which is a high-latitude region, and have a short DTH. Among the four known loci required for a short DTH, three loci had common alleles in A58 and Kitaake, implying there is a similar genetic basis for DTH between the two varieties. A genome-wide single nucleotide polymorphism (SNP) analysis based on the F4 population identified five new quantitative trait loci (QTL) associated with transgressive DTH phenotypes. Each of these QTL had different degrees of additive effects on DTH, and two QTL had an epistatic effect on each other. Thus, a genome-wide SNP analysis facilitated the detection of genetic loci associated with extreme DTH phenotypes, and revealed that the transgressive phenotypes were produced by exchanging the complementary alleles of a few minor QTL in the similar parental phenotypes.

Hybridization is a source of phenotypic novelty and variation because of increased additive genetic variation. Yet, the roles of nonadditive allelic interactions in shaping phenotypic mean and variance of hybrids have been underappreciated. Here, we examine the distributions of male‐mating traits in F1 hybrids via a meta‐analysis of 3208 effect sizes from 39 animal species pairs. Although additivity sets phenotypic distributions of F1s to be intermediate, F1s also showed recessivity and resemblance to maternal species. F1s expressed novel phenotypes (beyond the range of both parents) in 65% of species pairs, often associated with increased phenotypic variability. Overall, however, F1s expressed smaller variation than parents in 51% of traits. Although genetic divergence between parents did not impact phenotypic novelty, it increased phenotypic variability of F1s. By creating novel phenotypes with increased variability, nonadditivity of heterozygotic genome may play key roles in determining mating success of F1s, and their subsequent extinction or speciation. [ABSTRACT FROM AUTHOR]

Physicochemical traits, such as 100-seed weight (100-SW), water absorption ratio (WAR), sprouting and storage protein fractions of soybean (Glycine max (L.) Merr.) seeds, contribute to the quality of soy products processed from them. In the present investigation, 108 recombinant inbred lines (RILs) derived from LSb1 × NRC7 were genotyped using 105 polymorphic simple sequence repeat (SSR) markers across the genome. These RILs were phenotyped for 100-SW, WAR, sprout yield, hypocotyl length, and glycinin (11S), and β-conglycinin (7S) subunits of storage protein also. The study revealed common genomic regions governing multiple seed traits, besides the identification of quantitative trait loci (QTL) for individual seed traits. Of the seven QTL identified for 100-SW and 10 for WAR, five QTL were novel for both the traits. All four QTL identified for sprout yield and two QTL for 11S/7S ratio were novel. Five QTL were identified for multiple seed traits. These genomic regions common to different seed traits should be useful for pyramiding desirable traits for 100-SW, WAR, sprout yield, and 11S/7S ratio in the same genetic background for developing soybean varieties suitable for processing food products. [ABSTRACT FROM AUTHOR]

The phenomenon of transgressive segregation, where a small minority of recombinants are outliers relative to the range of parental phenotypes, is commonly observed in plant breeding populations. While this phenomenon has been attributed to complementation and epistatic effects, the physiological and developmental synergism involved have not been fully illuminated by the QTL mapping approach alone, especially for stress-adaptive traits involving highly complex interactions. By systems-level profiling of the IR29 × Pokkali recombinant inbred population of rice, we addressed the hypothesis that novel salinity tolerance phenotypes are created by reconfigured physiological networks due to positive or negative coupling-uncoupling of developmental and physiological attributes of each parent. Real-time growth and hyperspectral profiling distinguished the transgressive individuals in terms of stress penalty to growth. Non-parental network signatures that led to either optimal or non-optimal integration of developmental with stress-related mechanisms were evident at the macro-physiological, biochemical, metabolic, and transcriptomic levels. Large positive net gain in super-tolerant progeny was due to ideal complementation of beneficial traits while shedding antagonistic traits. Super-sensitivity was explained by the stacking of multiple antagonistic traits and loss of major beneficial traits. The synergism uncovered by the phenomics approach in this study supports the modern views of the Omnigenic Theory, emphasizing the synergy or lack thereof between core and peripheral components. This study also supports a breeding paradigm rooted on genomic modeling from multi-dimensional genetic, physiological, and phenotypic profiles to create novel adaptive traits for new crop varieties of the 21st century.

The phenomenon of transgressive segregation, where a small minority of recombinants are outliers relative to the range of parental phenotypes, is commonly observed in plant breeding populations. While this phenomenon has been attributed to complementation and epistatic effects, the physiological and developmental synergism involved have not been fully illuminated by the QTL mapping approach alone, especially for stress-adaptive traits involving highly complex interactions. By systems-level profiling of the IR29 × Pokkali recombinant inbred population of rice, we addressed the hypothesis that novel salinity tolerance phenotypes are created by reconfigured physiological networks due to positive or negative coupling-uncoupling of developmental and physiological attributes of each parent. Real-time growth and hyperspectral profiling distinguished the transgressive individuals in terms of stress penalty to growth. Non-parental network signatures that led to either optimal or non-optimal integration of developmental with stress-related mechanisms were evident at the macro-physiological, biochemical, metabolic, and transcriptomic levels. Large positive net gain in super-tolerant progeny was due to ideal complementation of beneficial traits while shedding antagonistic traits. Super-sensitivity was explained by the stacking of multiple antagonistic traits and loss of major beneficial traits. The synergism uncovered by the phenomics approach in this study supports the modern views of the Omnigenic Theory, emphasizing the synergy or lack thereof between core and peripheral components. This study also supports a breeding paradigm rooted on genomic modeling from multi-dimensional genetic, physiological, and phenotypic profiles to create novel adaptive traits for new crop varieties of the 21st century. [ABSTRACT FROM AUTHOR]

Summary: Transgressive segregation and heterosis are the reasons that plant breeding works. Molecular explanations for both phenomena have been suggested and play a contributing role. However, it is often overlooked by molecular genetic researchers that transgressive segregation and heterosis are most simply explained by dispersion of favorable alleles. Therefore, advances in molecular biology will deliver the most impact on plant breeding when integrated with sources of heritable trait variation – and this will be best achieved within a quantitative genetics framework. An example of the power of quantitative approaches is the implementation of genomic selection, which has recently revolutionized animal breeding. Genomic selection is now being applied to both hybrid and inbred crops and is likely to be the major source of improvement in plant breeding practice over the next decade. Breeders' ability to efficiently apply genomic selection methodologies is due to recent technology advances in genotyping and sequencing. Furthermore, targeted integration of additional molecular data (such as gene expression, gene copy number and methylation status) into genomic prediction models may increase their performance. In this review, we discuss and contextualize a suite of established quantitative genetics themes relating to hybrid vigour, transgressive segregation and their central relevance to plant breeding, with the aim of informing crop researchers outside of the quantitative genetics discipline of their relevance and importance to crop improvement. Better understanding between molecular and quantitative disciplines will increase the potential for further improvements in plant breeding methodologies and so help underpin future food security. [ABSTRACT FROM AUTHOR]

Sesame (Sesamum indicum L.) is produced worldwide, although more than 96% of the world sesame seed is produced in Africa and Asia. The objective of this study was to determine morphological properties and identify the genetic diversity of cultivated sesame genotypes grown in different parts of Ethiopia. Three hundred sesame genotypes collected from diverse ecologies of Ethiopia and introduced from different African and Asian countries, were used in this study. Genotypes showed wide variability for most morphological traits, except for plant growth type, leaf glands, anther filament colour, anther connective tip gland, and anthocyanin colouration of the capsule. Genetic divergence using Mahalanobis D2 statistics was computed, and the genotype lines were grouped into six different clusters. Clustering was not associated with the geographical distribution; instead genotypes were grouped mainly based on morphological differences. The lowest divergence was noticed between cluster I and V (10.06). Maximum inter-cluster distance was observed between clusters IV and VI (D2 =342.56, followed by clusters I and VI (D2 =217.9783), and III with IV (D2 =190.8707). Maximum genetic recombination and variation in the subsequent generation, is expected from crosses that involve parents from the clusters characterised by maximum distances. Thus, maximum distances or varation could maximise opportunities for transgressive segregation, since unrelated genotypes would contribute unique desirable alleles at different loci. [ABSTRACT FROM AUTHOR]

Genetic novelties are important nucleators of adaptive speciation. Transgressive segregation is a major mechanism that creates genetic novelties with morphological and developmental attributes that confer adaptive advantages in certain environments. This study examined the morpho-developmental and physiological profiles of recombinant inbred lines (RILs) from the salt-sensitive IR29 and salt-tolerant Pokkali rice, representing the total range of salt tolerance including the outliers at both ends of the spectrum. Morpho-developmental and physiological profiles were integrated with a hypothesis-driven interrogation of mRNA and miRNA transcriptomes to uncover the critical genetic networks that have been rewired for novel adaptive architecture. The transgressive super-tolerant FL510 had a characteristic small tiller angle and wider, more erect, sturdier, and darker green leaves. This unique morphology resulted in lower transpiration rate, which also conferred a special ability to retain water more efficiently for osmotic avoidance. The unique ability for water retention conferred by such adaptive morphology appeared to enhance the efficacy of defenses mediated by Na+ exclusion mechanism (SalTol-effects) inherited from Pokkali. The super-tolerant FL510 and super-sensitive FL499 had the smallest proportions of differentially expressed genes with little overlaps. Genes that were steadily upregulated in FL510 comprised a putative cytokinin-regulated genetic network that appeared to maintain robust growth under salt stress through well-orchestrated cell wall biogenesis and cell expansion, likely through major regulatory (OsRR23, OsHK5) and biosynthetic (OsIPT9) genes in the cytokinin signaling pathway. Meanwhile, a constitutively expressed cluster in FL510 prominently featured two transcription factors (OsIBH1, TAC3) that control tiller angle and growth habit through the brassinosteroid signaling pathway. Both the putative cytokinin-mediated and brassinosteroid-mediated clusters appeared to function as highly coordinated network synergies in FL510. In contrast, both networks appeared to be sub-optimal and inferior in the other RILs and parents as they were disjointed and highly fragmented. Transgressively expressed miRNAs (miR169, miR397, miR827) were also identified as prominent signatures of FL510, with functional implications to mechanisms that support robust growth, homeostasis, and osmotic stress avoidance. Results of this study demonstrate how genetic recombination creates novel morphology that complements inducible defenses hence transgressive adaptive phenotypes.

The studies on genetic variability, heritability and genetic advance was carried out with 720 plants of each F2 populations of four chickpea crosses. High mean performance, wider range of variation, high heritability coupled with moderate to high expected genetic advance as per cent of mean was observed for number of branches per plant, number of pods per plant and seed yield per plant in GJG 0315 x ICCV 96029, GJG 0107 x GCP 105 and GJG 0719 x SAKI 9516 of F2 populations, which indicated the predominant role of additive gene action in the expression of these three traits. Moderate heritability and low genetic advance was recorded for number of branches per plant, number of pods per plant and seed yield per plant in GAG 0419 x JCP 245. Greater number of transgressive segregants was found for number of branches per plant followed by days to flowering and days to maturity, number of pods per plant and seed yield per plant. A track on these transgressive segregants should be maintained and forwarded to further generations till they reach nearly homozygous condition. Most promising one can be used in further breeding programme.

Early elimination of poor crosses based on an objective criterion allows increased allocation of resources only to a few promising crosses for identifying superior recombinant inbred lines (RILs) for use as pure-line cultivars in self-pollinated crops. Early generation (F2:3) prediction of frequency of superior RILs that could be derived from advanced generations of crosses is one such criterion. We predicted the frequency of transgressive RILs from two horse gram crosses (namely HPKM 320 × CRIDA18-R and IC 361290 × Palem 1) for primary branches per plant, pods per plant, pod weight per plant and grain weight per plant based on mid parental value, additive genetic effects and additive genetic variance estimated from trait means of parents, and their F2 and F2:3 generations. The predicted frequency of RILs that transgressed better parent/two checks varied with the cross and the trait within a cross. The frequencies of transgressive RILs predicted from IC 361290 × Palem 1 were higher than those predicted from HPKM 320 × CRIDA 18-R for three of the four traits. As expected, the minimum population size required to recover the transgressive RILs predicted from IC 361290 × Palem 1 was relatively smaller than that from IC 361290 × Palem 1. Increased allocation of resources for handling segregating populations derived from IC 361290 × Palem 1 is expected to result in superior RILs for use as cultivars. We believe that the objective criterion used in our study is handy in identifying superior RILs in early segregating populations derived from a few promising crosses. [ABSTRACT FROM AUTHOR]

Breeding for thermotolerance in processes determining fruit set and pollen germination is increasingly needed as global warming progresses. We previously reported good yields at high temperatures from the F1 hybrid of the Capsicum chinense cultivars 'Sy-2' and 'No. 3686', both of which yield poorly at high temperatures. Moreover, the percentages of fruit set at high temperature in the F2 population segregated quantitively. In addition, percentages of fruit set in some F2 individuals exceeded those of the F1 hybrid. Analysis of the F2 population using double-digest restriction site-associated DNA sequencing (ddRAD-Seq) shows that the percentage of fruit set under high temperature is strongly associated to single nucleotide polymorphisms (SNPs) in a certain gene region of chromosome 6 and weakly associated to a gene region on the chromosome 3. Furthermore, the pollen germination rate is strongly associated to SNPs of the same regions on chromosomes 3 and 6. Analysis of the genotypes and traits in another F2 population shows that the genotype determined by the cleaved amplified polymorphic sequence marker designed on the candidate gene region is associated to the percentage of fruit set and the pollen germination rate at high temperatures, supporting the results of ddRAD-Seq. The presence of alleles from both the gene regions of chromosome 3 from 'No. 3686' and chromosome 6 from 'Sy-2' increased the percentage of fruit set additively. We suggest that genes controlling fruit set and pollen germination at high temperature are located in these two gene regions. [ABSTRACT FROM AUTHOR]

Genetic novelties are important nucleators of adaptive speciation. Transgressive segregation is a major mechanism that creates genetic novelties with morphological and developmental attributes that confer adaptive advantages in certain environments. This study examined the morpho-developmental and physiological profiles of recombinant inbred lines (RILs) from the salt-sensitive IR29 and salt-tolerant Pokkali rice, representing the total range of salt tolerance including the outliers at both ends of the spectrum. Morpho-developmental and physiological profiles were integrated with a hypothesis-driven interrogation of mRNA and miRNA transcriptomes to uncover the critical genetic networks that have been rewired for novel adaptive architecture. The transgressive super-tolerant FL510 had a characteristic small tiller angle and wider, more erect, sturdier, and darker green leaves. This unique morphology resulted in lower transpiration rate, which also conferred a special ability to retain water more efficiently for osmotic avoidance. The unique ability for water retention conferred by such adaptive morphology appeared to enhance the efficacy of defenses mediated by Na+ exclusion mechanism (SalTol -effects) inherited from Pokkali. The super-tolerant FL510 and super-sensitive FL499 had the smallest proportions of differentially expressed genes with little overlaps. Genes that were steadily upregulated in FL510 comprised a putative cytokinin-regulated genetic network that appeared to maintain robust growth under salt stress through well-orchestrated cell wall biogenesis and cell expansion, likely through major regulatory (OsRR23, OsHK5) and biosynthetic (OsIPT9) genes in the cytokinin signaling pathway. Meanwhile, a constitutively expressed cluster in FL510 prominently featured two transcription factors (OsIBH1, TAC3) that control tiller angle and growth habit through the brassinosteroid signaling pathway. Both the putative cytokinin-mediated and brassinosteroid-mediated clusters appeared to function as highly coordinated network synergies in FL510. In contrast, both networks appeared to be sub-optimal and inferior in the other RILs and parents as they were disjointed and highly fragmented. Transgressively expressed miRNAs (miR169, miR397, miR827) were also identified as prominent signatures of FL510, with functional implications to mechanisms that support robust growth, homeostasis, and osmotic stress avoidance. Results of this study demonstrate how genetic recombination creates novel morphology that complements inducible defenses hence transgressive adaptive phenotypes. [ABSTRACT FROM AUTHOR]

In order to facilitate the selection of new genotypes, diversity evaluation and analysis of relationships of effective traits on grain yield of rice in F2 populations produced by crossing of Anbarbo cultivar as mother parent with semi dwarf and highly produced by Shafagh and Najafi as paternal parents, 450 F2 genotypes with three control varieties (Anbarbo, Shafagh and Najafi) were evaluated and grain yield and 16 different agronomic traits were investigated. By comparing the descriptive statistics of the parental cultivars and the resulting F2 progenies, positive and negative transgressive segregation was observed for most traits such as yield, harvest index, peduncle length and number of fertile tillers. Dry weight of panicle, number of grains Eer plant, biological yield, number of fertile tillers and grain per panicle, harvest index, 100-grain weight, eight, panicle length and peduncle length had positive and significant correlations with grain yield. To select grain yield justifying traits, stepwise regression analysis was performed and dry weight of panicle,number of grain per plant, 100-grain weight, number of grains per panicle, first and second internode lengths were introduced into the model as the most effective traits on grain yield. Path coefficient analysis showed that the most direct and positive affecting traits were number of grains per plant (0.834), 100-grain weight (0.348) and dry weight of panicle (0.122), respectively. In this research, grain number per plant, 100-grain weight and dry weight of panicle were identified as selection indexes for improving grain yield in rice and recommended for use in rice modification projects. According to the phenotypic variation observed among F2 progenies for different traits (variation range and coefficient of variation) in this study and applying the desired segregation in breeding programs, it could be achieved new lines with the desired characteristics and increased yield in later generations. [ABSTRACT FROM AUTHOR]

The East African cichlid radiations are characterized by repeated and rapid diversification into many distinct species with different ecological specializations and by a history of hybridization events between nonsister species. Such hybridization might provide important fuel for adaptive radiation. Interspecific hybrids can have extreme trait values or novel trait combinations and such transgressive phenotypes may allow some hybrids to explore ecological niches neither of the parental species could tap into. Here, we investigate the potential of second‐generation (F2) hybrids between two generalist cichlid species from Lake Malawi to exploit a resource neither parental species is specialized on: feeding by sifting sand. Some of the F2 hybrids phenotypically resembled fish of species that are specialized on sand sifting. We combined experimental behavioral and morphometric approaches to test whether the F2 hybrids are transgressive in both morphology and behavior related to sand sifting. We then performed a quantitative trait loci (QTL) analysis using RADseq markers to investigate the genetic architecture of morphological and behavioral traits. We show that transgression is present in several morphological traits, that novel trait combinations occur, and we observe transgressive trait values in sand sifting behavior in some of the F2 hybrids. Moreover, we find QTLs for morphology and for sand sifting behavior, suggesting the existence of some loci with moderate to large effects. We demonstrate that hybridization has the potential to rapidly generate novel and ecologically relevant phenotypes that may be suited to a niche neither of the parental species occupies. Interspecific hybridization may thereby contribute to the rapid generation of ecological diversity in cichlid radiations. [ABSTRACT FROM AUTHOR]

The alleles used for adaptation can pleiotropically affect traits under stabilizing selection. The fixation of alleles with deleterious pleiotropic side effects causes compensatory alleles to be favored by selection. Such compensatory alleles might segregate in interpopulation hybrids, resulting in segregation variance for traits where parents have indistinguishable phenotypes. If adaptation typically involves pleiotropy and compensation, then the segregation variance for traits under stabilizing selection is expected to increase with the magnitude of adaptive phenotypic divergence between parents. This prediction has not been tested empirically, and I gathered data from experimental hybridization studies to evaluate it. I found that pairs of parents that are more phenotypically divergent beget hybrids with more segregation variance in traits for which the parents are statistically indistinguishable. This result suggests that adaptive divergence between pairs of natural populations proceeds via pleiotropy and compensation and that deleterious transgressive segregation variance accumulates systematically as populations diverge. [ABSTRACT FROM AUTHOR]

Haploid inducers are key components of doubled haploid (DH) technology in maize. Robust agronomic performance and better haploid induction ability of inducers are persistently sought through genetic improvement. We herein developed C1-I inducers enabling large-scale in vivo haploid induction of inducers and discovered superior inducers from the DH progenies. The haploid induction rate (HIR) of C1-I inducers ranged between 5.8% and 12.0%. Overall, the success rate of DH production was 13% on average across the 23 different inducer crosses. The anthesis-silking interval and days to flowering of inducer F 1 s are significantly correlated with the success rate of DH production (r = -0.48 and 0.47, respectively). Transgressive segregants in DH inducers (DHIs) were found for the traits (days to flowering, HIR, plant height, and total primary branch length). Moreover, the best HIR in DHIs exceeded 23%. Parental genome contributions to DHI progenies ranged between 0.40 and 0.55, respectively, in 25 and 75 percentage quantiles, and the mean and median were 0.48. The allele frequency of the four traits from inducer parents to DHI progenies did not correspond with the phenotypic difference between superior and inferior individuals in the DH populations by genome-wide Fst analysis. This study demonstrated that the recombinant DHIs can be accessed on a large scale and used as materials to facilitate the genetic improvement of maternal haploid inducers by in vivo DH technology., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Chen, Lübberstedt and Frei.)