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Sweet sorghum is a promising source of ethanol production. In this sense, the investigation of genetic diversity aims to direct heterotic crosses and identify populations that display transgressive segregation in advanced generations. For this, two experiments consisting of 10 sweet sorghum genotypes were installed in 2015/16 at the municipalities of Sinop, in the state of Mato Grosso (MT), and Passo Fundo, in the state of Rio Grande do Sul (RS), Brazil. The variables evaluated in this assessment comprised fresh mass production, dry mass production, Ethanol liters per hectare, soluble solid contents, plant height and flowering. The sweet sorghum performance and genetic diversity was estimated. Five genetic groups were observed. Fresh mass, Ethanol, flowering and height were significant for both locations, demonstrating the influence of environment on hybrid behavior. Crosses between genotypes 4x8 at Passo Fundo, and 9x10 at Sinop are favorable, as these genotypes exhibit good agronomic characteristics, especially for the main variable employed in the sugar-alcohol industry. Flowering contributed the most to genotype separation in both locations. Crosses between genotypes 4x8 and 4x9 are promising to obtain superior segregating populations for both environments, as they exhibited the greatest diversity-interfering contributions considering the investigated variables.

Bread wheat (Triticum aestivum L.) is an important cereal crop that provides >20% of the global calorie intake. Bread wheat contains micronutrients, and thus plays a significant role in nutritional and food securities especially in developing countries. However, its grains are inherently deficient in some micronutrients, particularly iron and zinc, which makes them important biofortification targets. Our objective was to investigate variations in micronutrients and their relationship with grain yield components in wheat under four environments in South Africa. A population of 139 doubled haploid lines derived from a cross between cvv. Tugela-DN and Elands was phenotyped for grain iron and grain zinc concentrations and grain yield components. Heat and drought conditions at Arlington resulted in higher grain zinc concentrations and lower yield component traits; the opposite trend was observed at Bethlehem and Harrismith for both micronutrients and yield components. All traits showed transgressive segregation. Grain iron and zinc concentrations were significantly positively correlated in all four environments. The correlations between these minerals and yield components were inconsistent and ranged from significant to insignificant depending on the environment, indicating that this relationship is non-genetic. The results demonstrate that biofortification of both grain iron and grain zinc can be included as part of the breeding objectives and will not necessarily have adverse relationships with grain yield components.

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 coloration. 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 color pattern in African cichlids, vertical bars, and potential interactions between the two color 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 color 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.

Significant variability is available in the F2 population of brinjal. Top crosses of brinjal Biliudda badane × mullu badane produced from F1 generation were in augmented design at ZARS Shimogga in Kharif 2017. They have several characteristics of plant breeding significance with sufficient scope for added improvement to growing conditions. The F2 study showed significant variation for nine quantitative traits. Close estimates between GCV and PCV values indicated lesser influence of environmental factors on the expression of traits under study. In this investigation, the proportion of genetic contribution of high GCV, PCV coupled with high broad sense heritability and genetic advance to the overall phenotypic expression of the studied traits like number of fruits per plant, number primary branches, number of flowers per plant was high, indicating predominant control of additive genes, and these traits could be improved upon by selection without progeny testing. High magnitude of heritability for most of the characters suggested the progress of improvement in yield and its components. Differences in mean values of parents for various characters indicated involvement of diverse parents in the crosses studied. The F2 plants exceeded either of the parents for most of the characters, which seems to be due to transgressive segregation.

Bacterial wilt caused by Ralstonia solanacearum is the main bacterial disease in potato. Solanum commersonii Dun. (cmm; 2n = 2x = 24, 1 EBN) is a native species to southern Brazil, Uruguay and Argentina with desirable traits for introgressive hybridisation breeding into cultivated potato such as resistance to R. solanacearum. In Uruguay, successful crosses between cmm and Solanum tuberosum Group Tuberosum (tbr; 2n = 4x = 48, 4 EBN) have been carried out with this objective, resulting in backcross 1, 2 and 3 progenies. The aim of this study was to characterise one backcross 3 progeny (BC3) using cytogenetic, genetic, morphological and agronomic descriptors. Resistance to R. solanacearum showed transgressive segregation and an association with plant architecture. Fifty-two percent of individuals had chromosome numbers close to cultivated potato with no evidence of preferential loss of cmm chromosomes. All BC3 individuals showed male sterility, probably due to nuclear-cytoplasmic interactions. Although there was wide segregation in morphological traits, most individuals resembled the recurrent tbr parents. A few more backcrosses combined with screening for bacterial wilt resistance may be necessary to allow for further recombination and removal of undesirable traits from cmm. The presence of BC3 individuals with chromosome numbers close to 2n = 48, combining morphological traits from tbr with good levels of resistance, suggests the occurrence of introgression events. This points to S. commersonii as one of the most promising genetic resources for potato breeding from the Southern Atlantic region.

The radial variation and the genetic variation of wood properties between the parents and offspring of Populus deltoides were studied in this work. The chemical composition, density, and anatomical characteristics of Populus deltoides cl. ‘Danhong’ and its offspring exhibited the phenomenon of transgressive segregation. The chemical compositions of the parents and offspring were decreased in several attributes (benzene alcohol extract, hemicelluloses, lignin) with the increase of the cambial age. Moreover, the fibre length, fibre width, ratio of fibre length to width, and wall thickness to lumen ratio of parents and offspring were increased with cambial age. In addition, the densities of parents and offspring were increased with the increase of cambial age. There were significant differences in wood properties among Populus deltoides and its hybrids. These results indicated that Populus deltoides cl. ‘Danhong’ could be considered as pulp material and Populus deltoides cl. ‘Nanyang’ as building material. According to the radial variation rule of each material character, the rotation cutting period can be selected as years 7 or 8.

We identified cryptic early blight resistance introgressions in tomato breeding lines and demonstrated efficient genotypic selection for resistance in the context of a tomato breeding program. Early blight is a widespread and problematic disease affecting tomatoes (Solanum lycopersicum). Caused by the fungal pathogen Alternaria linariae (syn. A. tomatophila), symptoms include lesions on tomato stems, fruit, and foliage, often resulting in yield losses. Breeding tomatoes with genetic resistance would enhance production sustainability. Using cross-market breeding populations, we identified several quantitative trait loci (QTL) associated with early blight resistance. Early blight resistance putatively derived from ‘Campbell 1943′ was confirmed in modern fresh market tomato breeding lines. This resistance offered substantial protection against early blight stem lesions (collar rot) and moderate protection from defoliation. A distinctive and potentially novel form of early blight foliar resistance was discovered in a processing tomato breeding line and is probably derived from S. pimpinellifolium via ‘Hawaii 7998’. Additional field trials validated the three most promising large-effect QTL, EB-1.2, EB-5, and EB-9. Resistance effects for EB-5 and EB-9 were consistent across breeding populations and environments, while EB-1.2’s effect was population specific. Using genome-wide marker-assisted backcrossing, we developed fresh market tomato lines that were near-isogenic for early blight QTL. Resistance in these lines was largely mediated by just two QTL, EB-5 and EB-9, that together captured 49.0 and 68.7% of the defoliation and stem lesion variance, respectively. Our work showcases the value of mining cryptic introgressions in tomato lines, and across market classes, for use as additional sources of disease resistance.

The wild species of rice, Oryza rufipogon, is a source of genetic variation for yield-enhancing traits and blast resistance. With the objective to genetically enhance the elite rice cultivar, ‘Samba Mahsuri’, a set of 192 BC2F2 and BC2F3 lines developed from O. rufipogon was characterized for yield-enhancing traits and blast resistance. The study revealed the presence of significant genetic variability and transgressive segregation for productive tillers, spikelets per panicle, and grain yield per plant. The study also identified several introgression lines superior to the recurrent parent for yield enhancing traits and blast resistance. Molecular characterization of 26 blast resistant lines identified multiple blast resistance genes in IL-136 [Pib, Pi9 (t), Pi54, Pi38, Pitp and Pi20(t)], IL-3 [Pib, Pi54, Pi38, Pitp and Pi20(t)], and IL-140 [Pib, Pi9(t), Pi54, Pi38, and Pitp]. Based on the performance of yield-enhancing traits and blast resistance, seven lines (IL-27, IL-28, IL-29, IL-72, IL-139, IL-158 and IL-171) showed merit. Estimation of the recovery of the recurrent parental genome by using 117 polymorphic SSR markers revealed that recurrent-parental genome recovery varied from 54.0 (IL-158) to 92.3% (IL-27). These promising, high-yielding introgression lines with multiple blast-resistance genes can serve as important genetic resources for yield and blast resistance improvement in rice, especially for the southern India.

A reduction in pod shattering is one of the main components of grain legume domestication. Despite this, many domesticated legumes suffer serious yield losses due to shattering, particularly under arid conditions. Mutations related to pod shattering modify the twisting force of pod walls or the structural strength of the dehiscence zone in pod sutures. At a molecular level, a growing body of evidence indicates that these changes are controlled by a relatively small number of key genes that have been selected in parallel across grain legume species, supporting partial molecular convergence. Legume homologs of Arabidopsis thaliana silique shattering genes play only minor roles in legume pod shattering. Most domesticated grain legume species contain multiple shattering-resistance genes, with mutants of each gene typically showing only partial shattering resistance. Hence, crosses between varieties with different genes lead to transgressive segregation of shattering alleles, producing plants with either enhanced shattering resistance or atavistic susceptibility to the trait. The frequency of these resistance pod-shattering alleles is often positively correlated with environmental aridity. The continued development of pod-shattering-related functional information will be vital for breeding crops that are suited to the increasingly arid conditions expected in the coming decades.

The available genetic variability in the studied germplasm may be used for direct selection or hybridization program. The experimental material comprised of F1 and F2 populations along with their respective parents of two intra-specific cotton crosses belonging to G. barbadense L., to estimate heritability, genetic advance as percent of mean and transgressive segregation for boll weight, seed cotton yield per plant, lint yield per plant, lint percentage, fiber length, fiber strength, fiber fineness and uniformity ratio. Variance of parents was lowest for all the studied traits suggesting thereby homogeneity within parents. But it abruptly increased in F2 population due to release of segregation variability. Most of the studied traits showed high heritability coupled with low genetic advance as percent of mean which indicated the predominant role of non-additive gene action in the expression of these traits. Both skewness and kurtosis had lower values and differ in the two crosses for studied traits. Lint yield / plant and lint % showed negative skewness sign and micronaire value had positive kurtosis sign for the two studied crosses. The two crosses had thrown maximum number of transgressive segregants over better parent for fiber length followed by micronaire value and boll weight, while, uniformity ratio had lowest number of transgressive segregants. The most promising transgressive segregants selected in F2 generation also to breakdown the negative correlation between high yield and fiber quality traits. The cotton breeder could be used indirect selection to improve these traits. These desirable selected plants had higher threshold value for the eight studied traits. A track on these transgressive segregants should be maintained and forwarded to further generations up to reach to homozygosity. Most promising one could be used in further breeding programme.

The triple test cross analysis was used to study different components of genetic variation by using 75 triple test cross families and their parents, F1 and F2 in one cotton cross (Giza 95 x Australy) for yield, its components and fiber quality traits. The 75 TTC families (25L1, 25L2 and 25L3) were sown at Sakha Experimental Station; Agriculture Research Center, Kafr El-Sheikh government; Egypt. Mean squares between L1, L2 and L3 were highly significant for all traits studied, while between L1 and L2 Families found to be significant for boll weight, lint percentage, lint index, fiber length and micronaire reading. Overall epistatic gene effects were highly significant differences for all traits studied except for fiber length and fiber strength. The (i) fixable type (additive × additive) was the most important epistatic effect than j and 1 non-fixable type for all traits. Both additive and dominance components were highly significant for all the traits studied. The degree of dominance was less than unity and confirmed the presence of partial dominance for all traits studied except for lint yield/plant; lint index and seed index were over-dominance. The Additive gene action played an important role in controlling inheritance for all traits studied than dominance one except for lint yield/plant; lint index and seed index. Direction of dominance (r) was non-significant for most traits indicating absence of dominance directional. Due to influence of (i) type of epistatic effects for the majority of the studied traits selection in early generations may be recommended. Genotypic correlation was positive and significant between yield traits and its components. This could help cotton breeder to use indirect selection to increase yield traits. All the studied traits showed higher proportion of recombinants inbreds falling outside parental range nearly 40%. So, these higher values of prediction revealed that it would be feasible to predict as early as possible for transgressive segregation which can surpass parental range for most studied traits.

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.

Cotton is grown in arid and semi-arid regions where abiotic stresses such as drought and salt are prevalent. There is a lack of studies that simultaneously address the genetic and genomic basis of tolerance to drought and salt stress. In this study, a multi-parent advanced generation inter-cross (MAGIC) population of 550 recombinant inbred lines (RILs) together with their 11 Upland cotton parents with a total of 473,516 polymorphic SNP markers was used to identify quantitative trait loci (QTL) for drought tolerance (DT) and salt tolerance (ST) at the seedling stage based on two replicated greenhouse tests. Transgressive segregation occurred in the MAGIC-RILs, indicating that tolerant and sensitive alleles recombined for tolerance to the abiotic stress during the intermating process for the population development. A total of 20 QTL were detected for DT including 13 and 7 QTL based on plant height (PH) and dry shoot weight (DSW), respectively; and 23 QTL were detected for ST including 12 and 11 QTL for PH and DSW, respectively. There were several chromosomes with QTL clusters for abiotic stress tolerance including four QTL on chromosome A13 and three QTL on A01 for DT, and four QTL on D08 and three QTL on A11 for ST. Nine QTL (21% of the 43 QTL) detected were in common between DT and ST, indicating a common genetic basis for DT and ST. The narrow chromosomal regions for most of the QTL detected in this study allowed identification of 53 candidate genes associated with responses to salt and drought stress and abiotic stimulus. The QTL identified for both DT and ST have significantly augmented the repertoire of QTL for abiotic stress tolerance that can be used for marker-assisted selection to develop cultivars with resilience to drought and/or salt and further genomic studies towards the identification of drought and salt tolerance genes in cotton.

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 ...

Cultivated lentil suffers yield loss from stemphylium blight, caused by Stemphylium botryosum Wallr. Identification of sources of stemphylium blight resistance and knowledge of the mode of inheritance of resistance are important for developing resistant cultivars. The interspecific recombinant inbred line (RIL) population developed from a cross between the moderately resistant parent Lens culinaris cv. ‘Eston’ and the resistant parent L. ervoides (Brign.) Grande accession IG 72815 was evaluated for stemphylium blight resistance under controlled conditions at the University of Saskatchewan, Saskatoon, Canada, and under field conditions at the Pulses Research Centre (PRC), Ishurdi, Bangladesh. We hypothesized that resistance from both parents will lead to transgressive segregation indicative of pyramiding of resistance genes from the same. However, no resistant transgressive segregants were observed in the RIL population. A large proportion (50%) of the RILs had disease severity levels similar to the resistant parent IG 72815 in experiments conducted under natural disease pressure in Bangladesh. Under controlled conditions in Saskatoon, 38% of RILs had resistance levels similar to IG 72815. Across all environments, 14 RILs consistently had resistance levels similar to IG 72815. The distribution of disease severity scores for all RILs indicated polygenic inheritance of stemphylium blight resistance in the population. RILs with consistent resistant reactions should prove useful for lentil improvement programmes. This will contribute to increasing the productivity of lentil crops in North America and the Indo-Gangetic region, which account for more than 68% of world lentil production.

Farinograph and mixograph-related parameters are key elements in wheat end-products quality. Understanding the genetic control of these traits and the influence of environmental factors such as heat stress, and their interaction are critical for developing cultivars with improved for those traits. To identify QTL for six farinograph and three mixograph traits, two double haploid (DH) populations (Yecora Rojo × Ksu106 and Klasic × Ksu105) were used in experiments conducted at Riyadh and Al Qassim locations under heat stress. Single nucleotide polymorphism (SNP) markers were used to determine the number of QTLs controlling these parameters. The genetic analysis of farinograph and mixograph-related traits showed considerable variation with transgressive segregation regardless of heat stress conditions in both locations. A total of 108 additive QTLs were detected for the six farinograph and three mixograph traits in the Yecora Rojo × Ksu106 population in both locations under heat treatments. These QTLs were distributed over all 21 wheat chromosomes except 3A. Similarly, in Klassic × Ksu105 population, there were an additional 68 QTLs identified over the two locations and were allocated on all chromosomes except 1D, 2A, 6A, and 6D. In population (Yecora Rojo × Ksu106), the QTL on chromosome 7A (Excalibur_c62415_288) showed significant effects for farinograph and mixograph traits (FDDT, FDST, FBD, M × h8, and M × t) under normal and heat stress condition at both locations. Interestingly, several QTLs that are related to farinograph and mixograph traits, which showed stable expression under both locations, were detected on chromosome 7A in population (Klassic × Ksu105). Results from this study show the quantitative nature of the genetic control of the studied traits and constitute a step toward identifying major QTLs that can be sued molecular-marker assisted breeding to develop new improved quality wheat cultivars.

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.

The bread-making quality traits of bread wheat underlie into genetic make-up of a variety and are influenced by environmental factors and their interaction. Identifying QTL that control bread-making traits in wheat under heat stress may help to develop cultivars that are improved for those traits. Two doubled haploid (DH) populations (Yecora Rojo × Ksu106 and Klasic × Ksu105) were used to identify QTL for eight bread-making traits in wheat under heat stress. The phenotyping of bread-making traits was performed under normal and heat stress conditions in Al-Qassim and Riyadh locations, Saudi Arabia. Single nucleotide polymorphism (SNP) markers have been used to determine the number of QTLs controlling the bread-making traits. The genetic analysis of bread-making traits showed considerable variation for measurable traits with transgressive segregation under normal and heat stress conditions in both locations. A total of 60 QTL explained 10–22% of phenotypic variation in the population (Klassic × KSU105). In the population (Yecora Rojo × KSU106), the 98 QTL explained 10–23% of phenotypic variation. In the population (Klassic × KSU105), eleven co-located QTLs were identified on chromosomes 2A, 3A, 3D, 5B and5D. The BBS QTL under heat stress co-located with QTLs for BCC and BSY under heat stress and normal conditions, respectively, in Riyadh location. Nineteen QTL clusters were identified on chromosomes 1D, 2A, 2B, 2D, 3B, 3D, 4A, 4D, 5A, 5B, 6A, 7A and 7D based on Map 2 in the population (Yecora Rojo × KSU106). Interestingly, one locus (JD_c4438_839) on the chromosome 5D was identified in both populations and was considered stable QTL. This locus was associated with QLFV.hs and QSLFV.hs in the population (Klassic × KSU105) and QLFW.n in the population (Yecora Rojo × KSU106). The finding of SNP marker (JD_c4438_839) has an important significant for marker-assisted selection of bread-making quality traits under heat stress.

Drought tolerance of plants is related to their root system architecture. The architecture of a mature plant root system is closely linked to seminal root growth at the seedling stage; hence, selection for root characteristics at the seedling stage may identify genotypes better suited for drought conditions. Here, the genetics of seminal root angle and number were investigated in three doubled haploid mapping populations of wheat. All populations showed significant phenotypic variation for both traits and each demonstrated transgressive segregation. In total, 34 genomic regions were associated with seminal root traits; however, most QTLs were variable from year to year and were population specific. Considering only the results consistent across both years of experiments, five QTLs for seminal root angle were identified on chromosomes 2DS, 5BS, 6AL, 7A, and 7BS, but only the 2DS QTL appeared in two of the three populations. For the seminal root number, one QTL was identified on 4BL. Correlation analyses for seminal root angle, number, and seed weight revealed interesting relationships to consider for future research. In one population, those interactions wrongfully identified QTLs for seed weight as QTLs for seminal root traits. Our findings demonstrate that seminal root angle and number are complex traits and despite high heritability, may be more difficult to unwind than previously proposed.

The Present study was carried out at Research cum Instructional Farm, Department of Genetics and Plant Breeding, Indira Gandhi Krishi Vishwavidyalaya, Raipur (M.P.) during rabi of 2015-16. The present study is based on a cross between GMU 244 x GMU 1303 and its F2 progeny study based on the segregation pattern of fatty acids and study of transgressive segregation. Over other allogamous oilseed crops, such as sunflower and rapeseed, safflower is characterized by high degree self-pollination which has greater advantage for commercial production of high oleic acid. It is a type of oilseed crop which consists of various composition of different fatty acids and this can be controlled by combination of various major genes and some changes in environment condition. The association of markers with traits of study is estimated by their positive average additive effect with different traits. In present study SSR marker SES 33 was found to be linked with number of seeds per capitulam and seed yield per plant. Similarly, SSR marker SF 18 was observed to be linked with plant height, number of branches per plant, number of capitulam per plant, seed yield per plant and oil %. SSR marker SES144 was found to be associated with yield contributing traits like plant height, number of capitulum per plant and oil %. SSR marker SES 99 was found to be associated with traits, plant height, and number of seeds per capitulam, seed yield per plant and oil %. In this study SSR marker SES 86 was observed to be linked with number of branches per plant and oil %. Marker SES 85 was found to be linked with number of branches per plant, oil %, number of seeds per capitulam and seed yield per plant. The SSR marker SES 81 was found to be linked with plant height.

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., 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. 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.

Earliness in crop plants has a crucial role in avoiding the stress of drought and heat, which are the most important challenging stressors in crop production and are predicted to increase in the near future due to global warming. Furthermore, it provides a guarantee of vegetable production in the short growing season of agricultural lands in the northern hemisphere and at high altitudes. The growing human population needs super early plant cultivars for these agricultural lands to meet future global demands. This study examined de novo super-early progeny, referred to as much earlier than that of the earlier parent, which flowered in 13–17 days and pod setting in 18–29 days after germination, discovered in F2 and studied up to F5 derived from interspecific crosses between garden pea (P. sativum L.) and the most distant relative of pea (P. fulvum Sibth. et Sm.). De novo super-early progeny were found to be earlier by about one month than P. sativum and two months than P. fulvum under short day conditions in the F5 population. In respect of days to flowering and pod setting, de novo super-early progeny had a relatively high level of narrow sense heritability (h2 = 82% and 80%, respectively), indicating that the selections for earliness in segregating populations was effective for improvement of extreme early maturing varieties. De novo super-early progeny could be grown under heat stress conditions due to the escape ability. Vegetable types were not only high yielding but also free of any known undesirable traits from the wild species, such as pod dehiscence and non-uniform maturity. It could be considered complementary to “speed breeding”, possibly obtaining more than six generations per year in a suitable climate chamber. Not only de novo super-early progeny but also transgressive segregation for agro-morphological traits can be created via interspecific crosses between P. sativum and P. fulvum, a precious unopened treasure in the second gene pool. Useful progeny obtained from crossing wild species with cultivated species reveal the importance of wild species.

Head smut (HS) is one of the most devastating diseases in spring maize growing region. To provide theoretical and applied basics for breeding resistant maize to HS, quantitative trait loci (QTL) for HS resistance was identified in this study. The resistant QTL to HS was studied by the F2:3 population derived from the cross T32 (highly resistant genotype) × HC (highly susceptible genotype). Analysis for each environment and joint analysis across three environments were used to identify QTL for the F2:3 population. A significant difference in HS resistance was found between inbred lines ‘T32’ and ‘HC’. A large genetic variation and transgressive segregation of the F2:3 population were observed among three different sites, Guian (GA), Huaxi (HX), and Pingba (PB). Two stable QTL for resistance to HS were detected in different environments, located in the interval umc1177 to umc2224 on chromosome 1 and in the interval umc1006 to nc013 on chromosome 6. Both of these QTL can be used for further marker-assisted selection (MAS) breeding and theoretical study of maize resistance to HS.

To develop crops capable of withstanding challenges posed by climate change, breeding strategies must focus on addressing multiple stresses occurring concurrently in plants. Leaf epidermal structures such as trichomes, stomata, and epidermal cells play an important role in mediating plant defense and could be essential traits that impart wide-ranging tolerance to biotic and abiotic stresses. Consequently, it is important to inform on the underlying diversity in these traits in lentil germplasm (Lens spp.). In this study, we characterized foliar microstructures of 12 genotypes belonging to seven wild and cultivated Lens species. We performed scanning electron microscopy on leaflet and pod surfaces for their qualitative characterization. For quantitative characterization, we observed surface imprints via light microscopy and quantified trichome density (TD), trichome length (TL), stomatal density (SD), epidermal cell density (ECD), and stomatal index (SI) on adaxial and abaxial leaflet surfaces for each genotype. We also assessed the heritability of trichome traits by evaluating interspecific recombinant inbred lines (RILs) derived from the cross Lens culinaris CDC Redberry × Lens tomentosus IG 72805. Comparing foliar microstructures, we found that TD and TL varied widely among cultivated and wild lentil genotypes. However, in most lentil genotypes, the adaxial leaflet surface had lower TD and longer trichomes compared to the abaxial surface. Pubescence on pods comprised five major phenotypes: no trichomes or glabrous pods, very short trichomes at low density, short trichomes at high density, medium-length trichomes at high density, and long trichomes at high density. Leaves of all species were amphistomatous, and SI, SD, and ECD were all higher on the adaxial compared to the abaxial surface. Adaxial surfaces had slightly sunken stomata, which might be an adaptive trait to conserve water. Quantifying TD and TL on the leaflets of interspecific RILs revealed transgressive segregation of these traits, suggesting that TD and TL are quantitative in nature. While taxonomic implications of this study are limited, a detailed description of agronomically relevant morphophysiological traits presented in this paper along with the mode of inheritance of trichomes may serve as a resource for scientists developing lentil adapted to concurrent biotic and abiotic stresses of the future.

The present work aimed to study the effect of two cycles of pedigree selection for highly grain yield in two segregating populations of wheat under water stress, during the two winter seasons of 2015/2016 and 2016/2017at Toshka Research Station, Desert Research Center, Aswan, Egypt. The water treatments were 100 and 67% of the irrigation requirements of wheat in Toshka as normal and drought condition, respectively. A transgressive segregation in both populations for all studied traits inducted the suitability of those material for pedigree selections. The genetic advanced for grain yield/plant and its components were greater in population 2 than in population 1 in the first cycle in pedigree selection. Highly significant differences among the selected families for all the studies traits were observed in both populations under normal and drought conditions. After one cycles of selection, the broad sense heritability was very high for most traits and reached 77.79 and 92.02% for grain yield/plant under normal irrigation, while were 87.53 and 93.12% under drought stress in population 1 and population 2, respectively. Two cycles of pedigree selection for grain yield/plant was enough to detect the best families and could be performed in the early segregating generations. It could be concluded that single trait selection was efficient to improve the selection criteria in these populations. These genotypes could be sources for drought tolerance.

Hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) is widely used for turf throughout subtropical and tropical climates because of its superior quality and performance. Development of cultivars adapted to broad range of environments is the main goal of many breeding programs. There is large variation for turfgrass characteristics and drought resistance among native bermudagrass (C. dactylon) germplasm originating from the Mediterranean region. Hence, the aim of this study was to develop triploid turf-type bermudagrass hybrids by making use of native genetic resources. Drought resistant tetraploid C. dactylon genotypes originating from the Mediterranean coastal region of Turkey were crossed with a diploid accession of C. transvaalensis from South Africa in 2011 and 2012. The hybrids were first identified using SRAP molecular markers. Then, phenotypic pre-selection was made for leaf shape, color and density and 273 hybrids were transplanted into the field. Two SSR markers further confirmed the true hybridity of 170 (62%) of these genotypes. Establishment rates in 2013, and turfgrass characteristics in 2014 and 2015 were recorded. Transgressive segregation was evident for estabilishment rate, turfgrass quality and color, and shoot density among progenies. Correlation analysis indicated that selection for shoot density, leaf texture, and prostrate growth habit could increase turf quality. The genotypes ‘45’ and ‘150’ were identified as promising parents for future breeding efforts as they provided positive general combining ability. The best ten hybrids with acceptable turfgrass characteristics were evaluated further under replicated field trials and line T4-C3 has just been released for commercial use.

Soybean (Glycine max [L.] Merr.) is an important source of human dietary protein and vegetable oil. A strong negative correlation between protein and oil contents has hindered efforts to improve soybean seed quality. The metabolic and genetic bases of soybean seed composition remain elusive. We evaluated metabolic diversity in a soybean near-isogenic line (NIL) population derived from parents (JD12 and CMSD) with contrasting seed oil contents. Using GC-TOF/MS, we compared seed primary metabolites of high protein/low oil lines, low protein/high oil lines, and their parents. Principal-components analysis showed that metabolic profiles of all progeny lines could be discriminated based on protein and oil contents. Univariate analysis revealed wide variation and transgressive segregation of metabolites in the population. Twenty-eight annotated metabolites, in particular free asparagine, free 3-cyanoalanine, and L-malic acid, were correlated with seed protein content or seed oil content or seed protein and oil content. These results shed light on the metabolic and genetic basis of soybean seed composition. Keywords: Metabolomics, Seed composition, Protein, Oil, Near-isogenic population

A population of 206 recombinant inbred lines (RILs F9–F10) derived from wheat cross WL711/C306 was phenotyped for morpho-physiological traits such as flag leaf area (FLA), flag leaf length (FLL), flag leaf width (FLW), and cell membrane stability (CMS) under water deficit stress (WDS) environment. High yielding cultivar, WL711 had higher FLA than the medium yielding cultivar C306 across trials under both environments. Parent cultivar C306 maintained membrane integrity while WL711 showed higher membrane damage under WDS. The RIL population showed considerable variation, normal distribution and transgressive segregation for FLA, FLL, FLW and CMS under WDS. The genetic linkage map of WL711/C306 RIL population was constructed comprising of 346 markers. The total map distance was 4526.8 cM with an averaged interval of 12.9 cM between adjacent markers. Major consistent QTL for FLA, FLL, FLW, and CMS were identified on chromosomes 2DS and 3BS respectively in the WL711/C306 RIL population under WDS. The major QTL for FLA, qFLAWD.2D.1 which expressed in multiple environments and for CMS, qCMSWD.3B.3 and qCMSWD.3B.4, accounted for a large proportion of phenotypic variance (PV) with positive allele being contributed by C306, a drought resistant (DR) parent. QTL qFLAWD.2D.1 for FLA co-located with QTL for grain number (GN) and days to flowering (DTF) while QTL qCMSWD.3B.3 and qCMS.3B.4 co-located with QTL for grain yield and its components, days to flowering, canopy temperature and coleoptiles length as reported in our previous publications on the WL711/C306 population (Shukla et al. in Euphytica 203:449–467, 2015; Singh et al. in J Plant Biochem Biotechnol 24:324–330, 2015). Two candidate genes Ghd7 for grain yield and heading date and OsCDK4 for calcium dependent protein kinases were identified in the 2DS and 3BS QTL regions respectively on comparison with gene content of rice chromosomes 7 and 1 respectively. Hence, QTLs qFLAWD.2D.1 and qCMSWD.3B.3 are potential target regions for fine mapping and marker assisted selection for FLA and CMS respectively in wheat under water deficit environments.

Phenotypic characteristics, as well as the relation between carotenoid accumulation and gene expression during ripening were determined in fruits of five new hybrids between tangor cv. ‘Murcott’ and sweet orange cv. ‘Pera’. The genotypes were classified into the orange-like group, showing mainly epoxycarotenoids, oval fruit shape and yellowish color, or in the mandarin-like group, showing mainly β-cryptoxanthin, flattened shape and deep-orange coloration; although some hybrids presented intermediate characteristics. The diversity in carotenoid composition of hybrids and genitors were mostly explained by patterns of gene expression. High carotenoid (250–426 μg/g dry weight [dw]) and β-cryptoxanthin (81–125 μg/g dw) contents, observed in the mandarin-like group, were generally associated with high expression of upstream genes (GGPPS1, PSY, PDS). On the other hand, low expression/repression of these genes and high expression of downstream genes (BCHX and ZEP) were associated with low carotenoid (~158 μg/g dw) and β-cryptoxanthin (5–22 μg/g dw) contents and epoxycarotenoid accumulation, as occurred in the orange-like group. Breeding experiments resulted in hybrids with outstanding higher carotenoid contents than both genitors (up to 426 μg/g dw versus 158–250 μg/g dw in genitors), which was attributed to transgressive segregation. Differences among genotypes have great impact on commercial fruit quality and potential health benefits, such as the provitamin A content.

Wild relatives of safflower (Carthamus tinctorius L.) may contribute genes to improve cultivated species under water stress conditions. This study was conducted to increase genetic diversity of safflower for agromorphological traits and fatty acid profiles using interspecific hybridization. Three species—C. tinctorius, C. palaestinus Eig., and C. oxyacanthus M. Bieb.—were used to develop three segregating populations of C. tinctorius × C. palaestinus (TP), C. oxyacanthus × C. palaestinus (OP), and C. oxyacanthus × C. palaestinus (TO). Seventy-three lines, along with the three parental species, were evaluated for agromorphological traits under water stress and nonstress conditions in F₃ and F₄ generations during 2 yr. Fatty acid analysis of interspecific progenies showed occurrence of transgressive segregation. The results showed that mean values of seed yield for TP and TO progenies, where C. tinctorius was one of their parents, were higher than mean value of seed yield for OP that derived from the two wild species. High genetic variation was observed for seed yield, capitulum diameter, and phenological traits in interspecific populations under both moisture conditions. Indirect selection for flowering and seed yield components under water deficit conditions was most efficient to improve seed yield. Results indicated that gene introgression from wild relatives of safflower into the cultivated gene pool increased genetic variation for the measured traits and allowed identifying superior genotypes for future breeding programs.

Zoysia germplasm exhibit different levels of sensitivity to fluazifop-P-butyl, but the genetic factors responsible for such differences are unknown. Segregation patterns of the fluazifop-P-butyl tolerance trait were studied under greenhouse conditions. In total, 244 F1 lines were generated from multiple crosses between the tolerant line 5337-2 (non–target site tolerance) and three more-sensitive lines (123, 252, and 5330-23). Progeny segregation showed that fluazifop-P-butyl tolerance within zoysiagrass (Zoysia spp.) is expressed as a quantitative trait with a wide range of intermediate phenotypes between parental phenotypes. Transgressive segregation was extensive and largely favored susceptibility in most families, but was especially evident for 5337-2 × 123 and 5337-2 × 5330-23. The segregation patterns for biomass reduction and percent injury were different within reciprocal crosses and among three different family crosses. Reciprocal effects were observed in growth reduction for 5337-2 × 5330-23, in percent injury at 3 wk after the treatment (WAT), and for 5337-2 × 252 at 6 WAT. This indicated that fluazifop-P-butyl tolerance was not completely controlled by nuclear genetic factors in 5337-2 and maternal/cytoplasmic inheritance was also partially responsible. These results suggested that fluazifop-P-butyl tolerance may be attributed to multiple genetic mechanisms, which could present a challenge for future breeding efforts because of the difficulty of fixing multiple traits within a breeding population.

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.

Heterosis might be used in a strategic way to increase yields of flue-cured tobacco (Nicotiana tabacum L.), but previous reports have suggested levels of heterosis to be low for F₁ hybrids of this market class. Based on analysis of a 14-parent diallel, we found average levels of F₁ midparent heterosis to be 10.3%, a level that is substantially higher than previous estimates from the 1960s. Thirteen of ninety-one tested hybrids significantly outyielded the highest yielding parental lines. Heterosis might also be an indicator of superior allelic complementation by parental lines that, in principle, could be fixed in derived inbred lines. We compared F₃:₄ families derived from three high heterotic crosses and three low heterotic crosses and observed positive correlations between F₁ heterosis and desirable transgressive segregation. Hence, the data support the use of F₁ heterosis as a predictor of breeding crosses with increased potential for desired outcomes. Several derived F₃:₄ families exhibited yields that were comparable with, or significantly better than, corresponding heterotic F₁ hybrids, indicating that heterotic effects could be fixed within inbred lines. Results suggest a reconsideration of heterosis for increasing yields of flue-cured tobacco.

Pigeonpea breeding activities started about a century ago and for decades only late maturing cultivars dominated the global cultivation. Historically, no early maturing cultivar was available for a very long time and breeding of such varieties started in the third quarter of 20th century but at a low key. From these efforts, some pigeonpea varieties maturing in 90–150 days were bred. Information gathered from various sources revealed that the first few early maturing genotypes originated through spontaneous mutations in the late maturing field‐grown landraces. In other cases, transgressive segregation and induced mutations also produced early maturing varieties. At present, the high yielding early maturing cultivars are contributing significantly towards widening the adaption barriers and in the diversification of some age‐old cropping systems. In this paper, the authors, besides discussing the importance of early maturing cultivars in present agricultural systems, also summarize information related to the origin of primary sources of earliness.

Adaptation of pigeonpea [Cajanus cajan (L.) Millspaugh], a short-day species, is restricted due to its sensitivity to photo-period. Earliness in this crop is reported to be linearly associated with photo-insensitivity; and this provides an opportunity to breed widely adapted cultivars through the selection for earliness. This research note reports breeding of the earliest maturing pigeonpea germplasm at ICRISAT. This germplasm, nicknamed as ‘super early’ and bred through the selection of transgressive segregants matured in

Haploid genome doubling is a key limiting step of haploid breeding in maize. Spontaneous restoration of haploid male fertility (HMF) provides a method by which costs can be saved and which does not require the use of toxic chemicals, in contrast to the artificial doubling process. To reveal the genetic basis of HMF, haploids were obtained from the offspring of 285 F2:3 families, derived from the cross Zheng58×K22. The F2:3 families were used as female donor and YHI-1 as the male inducer line. The rates of HMF from each family line were evaluated at two field sites over two planting seasons. Quantitative trait loci (QTL) for HMF were identified using a genetic linkage map containing 157 simple sequence repeat (SSR) markers. QTL for HMF displayed incomplete dominance. Transgressive segregation of haploids from F2:3 families was observed relative to haploids derived from the two parents of the mapping population. A total of nine QTL were detected, which were distributed on chromosomes 1, 3, 4, 7, and 8. Three QTL, qHMF3b, qHMF7a, and qHMF7b were detected in both locations, respectively. In our mapping population, HMF was controlled by three major QTL. These QTL could be useful to predict the ability of spontaneous haploid genome doubling in related breeding materials, and to accelerate the haploid breeding process by introgression or aggregation of those QTL.

Shape of almond kernel has an important impact in the final commercial value. Elliptic shapes are more common while round shapes, ‘Marcona’ types, are scarce and very appreciated. In order to increase the efficiency of the breeding programs for specific shape is important to know the genetic control of this trait. In this work, heritability of length, width, thickness, roundness and globosity, of shell and kernel, was estimated by midparent-offspring regression (narrow sense, h2) and by variance components analysis (broad sense, H2) for three years, using full-sib and half-sib offsprings coming from four crosses designed only for this objective. Length and roundness of shell and kernel showed the highest heritability by both methods every year, being intermediate or very low for the other traits. Kernels were usually less rounded than their shells. Values near one of the ratio h2/H2 were observed for length and roundness, showing an absence of non-additive effects for these two traits. In general, a normal phenotypic distribution was observed for all the traits and certain transgressive segregation was observed in the descendants. The results confirmed the complex architecture of this trait transmitted quantitatively, where additive effects play the mayor role.

Rice grain shape and nutritional quality traits have high economic value for commercial production of rice and largely determine the market price, besides influencing the global food demand for high-quality rice. Detection, mapping and exploitation of quantitative trait loci (QTL) associated with kernel elongation and grain quality in Basmati rice is considered as an efficient strategy for improving the kernel elongation and grain quality trait in rice varieties. Genetic information in rice for most of these traits is scanty and needed interventions through the use of molecular markers. A recombinant inbred lines (RIL) population consisting of 130 lines generated from the cross involving Basmati 370, a superior quality Basmati variety and Pusa Basmati 1121, a Basmati derived variety were used to map the QTLs for 9 important grain quality and yield related traits. Correlation studies showed that various components of yield show a significant positive relationship with grain yield. A genetic map was constructed using 70 polymorphic simple sequence repeat (SSR) markers spanning a genetic distance of 689.3 cM distributed over 12 rice chromosomes. Significant variation was observed and showed transgressive segregation for grain quality traits in RIL population. A total of 20 QTLs were identified associated with nine yield and quality traits. Epistatic interactions were also identified for grain quality related traits indicating complex genetic nature inheritance. Therefore, the identified QTLs and flanking marker information could be utilized in the marker-assisted selection to improve kernel elongation and nutritional grain quality traits in rice varieties.

Background Water supply limits agricultural productivity of many crops including lettuce. Identifying cultivars within crop species that can maintain productivity with reduced water supply is a significant challenge, but central to developing resilient crops for future water-limited climates. We investigated traits known to be related to water-use efficiency (WUE) and yield in lettuce, a globally important leafy salad crop, in a recombinant inbred line (RIL) lettuce mapping population, produced from a cross between the cultivated Lactuca sativa L. cv. Salinas and its wild progenitor L. serriola L. Results Wild and cultivated lettuce differed in their WUE and we observed transgressive segregation in yield and water-use traits in the RILs. Quantitative trait loci (QTL) analysis identified genomic regions controlling these traits under well-watered and droughted conditions. QTL were detected for carbon isotope discrimination, transpiration, stomatal conductance, leaf temperature and yield, controlling 4–23 % of the phenotypic variation. A QTL hotspot was identified on chromosome 8 that controlled carbon isotope discrimination, stomatal conductance and yield under drought. Several promising candidate genes in this region were associated with WUE, including aquaporins, late embryogenesis abundant proteins, an abscisic acid-responsive element binding protein and glutathione S-transferases involved in redox homeostasis following drought stress were also identified. Conclusions For the first time, we have characterised the genetic basis of WUE of lettuce, a commercially important and water demanding crop. We have identified promising candidate genomic regions determining WUE and yield under well-watered and water-limiting conditions, providing important pre-breeding data for future lettuce selection and breeding where water productivity will be a key target.

Populations derived from intraspecific crosses within two mint species of Mentha spicata and M. longifolia, were studied for genetic and phenotypic coefficients of variation, heritabilities, and genetic advances in various traits including plant height, fresh and dry weights, number of branches per plant, plant canopy diameter, leaf area, and essential oil content and yield. The majority of agro-economic characters showed high heritability (h2) and genetic advances in the F2 generation. The maximum genetic advance and genotypic coefficient of variation were recorded for fresh weight, leaf area, and essential oil content and yield. Based on these traits, total flavonoid (TFC) and phenolic (TPC) contents of the best genotypes from each species of M. longifolia and M. spicata were estimated. The results showed that some of the F2 plants had a higher amount of TFC and TPC compared with the parents. The analysis of essential oil components also revealed that the amount of piperitenone and menthone in M. longifolia and carvone and limonene in M. spicata significantly increased in the selected genotypes derived from intraspecific crosses. It is hypothesized that the improvements in the offspring derived from intraspecific crosses of mint are attributed to transgressive segregation and heterosis. Therefore, crossing within mint species can be effectively utilized for recombination breeding to obtain genotypes with a novel genetic structure potentially usable in breeding programs for pharmaceutical purposes.

Hybridization is a source of phenotypic novelty and variation because of increased additive genetic variation. Yet, the roles of non-additive 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 3,208 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. While genetic divergence between parents did not impact phenotypic novelty, it increased phenotypic variability of F1s. By creating novel phenotypes with increased variability, non-additivity of heterozygotic genome may play key roles in determining mating success of F1s, and their subsequent extinction or speciation. This article is protected by copyright. All rights reserved.

38 Pags.- 13 Figs.- 2 Tabls. The definitive version is available at: https://www.sciencedirect.com/science/journal/11610301, Genetic gains in wheat yield are required to meet future demand. In order to design strategic crosses, it is essential to quantify the genetic variation among elite cultivars on traits responsible for the adaptation and the generation of yield components. We explored the degree of variation within well-adapted commercial cultivars on developmental phases (vegetative, early reproductive and late reproductive), final leaf number and phyllochron, leaf and spikelet plastochron, number of spikelets, florets, and dynamics of floret primordia development. Variation in flowering time among cultivars was minor but they differed in the partitioning of that time into particular phases. Main differences were found for the length of the late reproductive phase, partly linked to those in final leaf number. Variations on number of fertile florets at anthesis were mostly explained by floret survival, due to differential ability of labile florets to maintain normal development between cultivars. These differences were related to the duration of the floret development, but not to the synchrony of development among florets. These findings provide useful information for breeders when selecting genotypes for strategic crosses, as considering floret survival through duration of floret development in one of the parents (for which these processes shall be characterised in the elite germplasm) might increase the likelihood of transgressive segregation towards high-yielding offspring., Funding was provided by ADAPTAWHEAT (a project funded by the European Commission under the 7th Framework Programme for Research and Technological Development) and by project AGL2012- 35300 funded by the Ministry of Economy and Competitiveness of Spain. HO held a FPI scholarship from the Spanish Ministry of Science and Innovation, and PP held a PhD scholarship from the University of Lleida.

Genetic variation in growth over the course of the season is a major source of grain yield variation in wheat, and for this reason variants controlling heading date and plant height are among the best-characterized in wheat genetics. While the major variants for these traits have been cloned, the importance of these variants in contributing to genetic variation for plant growth over time is not fully understood. Here we develop a biparental population segregating for major variants for both plant height and flowering time to characterize the genetic architecture of the traits and identify additional novel QTL. We find that additive genetic variation for both traits is almost entirely associated with major and moderate-effect QTL, including four novel heading date QTL and four novel plant height QTL.FT2andVrn-A3are proposed as candidate genes underlying QTL on chromosomes 3A and 7A, whileRht8is mapped to chromosome 2D. These mapped QTL also underlie genetic variation in a longitudinal analysis of plant growth over time. The oligogenic architecture of these traits is further demonstrated by the superior trait prediction accuracy of QTL-based prediction models compared to polygenic genomic selection models. In a population constructed from two modern wheat cultivars adapted to the southeast U.S., almost all additive genetic variation in plant growth traits is associated with known major variants or novel moderate-effect QTL. Major transgressive segregation was observed in this population despite the similar plant height and heading date characters of the parental lines. This segregation is being driven primarily by a small number of mapped QTL, instead of by many small-effect, undetected QTL. As most breeding populations in the southeast U.S. segregate for known QTL for these traits, genetic variation in plant height and heading date in these populations likely emerges from similar combinations of major and moderate effect QTL. We can make more accurate and cost-effective prediction models by targeted genotyping of key SNPs.