Paternal Parent Research Articles

Heterosis and genetic diversity in the crossings of gladiolus cultivars Amsterdam and White Prosperity

Abstract Gladiolus is one of the most important and popular cut-flower bulbous in Iran. The aim of this research was to produce new, high-quality hybrids through hybridization. We generated two promising hybrids (OPRC16 and OPRC57) combination from the varieties “Amsterdam” and “White Prosperity”. The Research was conducted in Ornamental Plants Research Center in Mahallat from 2014 to 2018. Values of Hm for traits were defined as the difference between the mid-F1 value and the mid-parent value, Mean Mid-parent Heterosis (MPH) or (Hmp) and High Parent Heterosis (HPH) or (Hsp). The results showed that the morphological analysis revealed the heredity and variation in the promising hybrids. The results for the hybrid OPRC16 showed that the Hm and Hmp values were negative for peduncle length but positive for other traits. The Hsp value was observed to be negative for the traits of peduncle length, leaf width, stem diameter, and cormels diameter, but it was positive for other traits. According to the results for the hybrid OPRC57, the Hm and Hmp values were negative for plant height, floret number, peduncle length, floret diameter, stem diameter, spike length, cormles weight, and cormlet diameter and negative for other traits. Peduncle length was positive in other traits. The Hmp value was negative for peduncle length, but positive for other traits. The Hsp value was recorded to be positive for leaf length, bud diameter, vase life, cormlet number, and cormles yield but negative for other traits. All in all, OPRC57 showed a negative heterosis in most traits. Based on the results, when ‘Amsterdam’ is used as the maternal plant in crosses, it has more positive heterosis effects than when it is used as the paternal parent. These results indicate that major of traits in the phenotypic and genetic diversity coefficient was very low, indicating that they had less environmental effects, since the genotypes were cultivated under similar and controlled conditions.

A pentaploid-based linkage map of the ancestral octoploid strawberry Fragaria virginiana reveals instances of sporadic hyper-recombination

The first high-resolution genetic linkage map of the ancestral octoploid (2n = 8x = 56) strawberry species, Fragaria virginiana, was constructed using segregation data obtained from a pentaploid progeny population. This novel mapping population of size 178 was generated by crossing highly heterozygous F. virginiana hybrid “LB48” as a paternal parent with diploid (2n = 2x = 14) Fragaria vesca “Hawaii 4”. The LB48 linkage map comprises 6055 markers genotyped on the Axiom® IStraw90 strawberry SNP array. The map consists of 28 linkage groups (LGs) organized into seven homoeology groups of four LGs each, and excludes a small 29th LG of undefined homoeology. One member of each homoeology group was assignable to an “A” subgenome associated with ancestral diploid Fragaria vesca, while no other subgenomes were defined. Despite an intriguing discrepancy within homoeology group VI, synteny comparisons with the previously published Fragaria ×ananassa DA × MO linkage map revealed substantial agreement. Following initial map construction, examination of crossover distributions revealed that six of the total 5162 (=29 chromosomes/individual × 178 individuals) chromosomes making up the data set exhibited abnormally high crossover counts, ranging from 15 to 48 crossovers per chromosome, as compared with the overall mean of 0.66 crossovers per chromosome. Each of these six hyper-recombinant (HypR) chromosomes occurred in a different LG and in a different individual. When calculated upon exclusion of the six HypR chromosomes, the canonical (i.e., broadly representative) LB48 map had 1851 loci distributed over a total map length of 1873 cM, while their inclusion increased the number of loci by 130, and the overall map length by 91 cM. Discovery of these hyper-recombinant chromosomes points to the existence of a sporadically acting mechanism that, if identified and manipulable, could be usefully harnessed for multiple purposes by geneticists and breeders.

Construction of an anchoring SSR marker genetic linkage map and detection of a sex-linked region in two dioecious populations of red bayberry

Red bayberry (Morella rubra) is an evergreen fruit tree found in southern China whose whole-genome sequence has recently been published. We updated the linkage map of the species by adding 118 SSR markers and the female-specific marker MrFT2_BD-SEX. The integrated map included eight linkage groups and spanned 491 cM. Eleven sex-associated markers were identified, six of which were located in linkage group 8, in agreement with the previously reported location of the sex-determining region. The MrFT2_BD-SEX marker was genotyped in 203 cultivated accessions. Among the females of the accessions, we found two female-specific alleles, designated W-b (151 bp) and W-d (129 bp). We previously found that ‘Dongkui’, a female cultivar, could produce viable pollen (we refer to such plants ‘Dongkui-male’) and serve as the paternal parent in crosses. The genotypes of the MrFT2_BD-SEX marker were W-b/Z in ‘Biqi’ and W-d/Z in ‘Dongkui-male’. The progeny of a cross between these parents produced a 3:1 female (W-) to male (ZZ) ratio and the expected 1:1:1:1 ratio of W-b/W-d: W-b/Z: W-d/Z: Z/Z. In addition, the flowering and fruiting phenotypes of all the F1 progeny fit their genotypes. Our results confirm the existence of ZW sex determination and show that the female phenotype is controlled by a single dominant locus (W) in a small genomic region (59 kb and less than 3.3 cM). Furthermore, we have produced a homozygous “super female” (WW) that should produce all-female offspring in the F2 generation, providing a foundation for commercial use and presenting great potential for use in modern breeding programs.

Genotype calling of triploid offspring from diploid parents

BackgroundPolyploidy is widespread in animals and especially in plants. Different kinds of ploidies exist, for example, hexaploidy in wheat, octaploidy in strawberries, and diploidy, triploidy, tetraploidy, and pseudo-tetraploidy (partly tetraploid) in fish. Triploid offspring from diploid parents occur frequently in the wild in Atlantic salmon (Salmo salar) and, as with triploidy in general, the triploid individuals are sterile. Induced triploidy in Atlantic salmon is common practice to produce sterile fish. In Norwegian aquaculture, production of sterile triploid fish is an attempt by government and industry to limit genetic introgression between wild and farmed fish. However, triploid fish may have traits and properties that differ from those of diploids. Investigating the genetics behind traits in triploids has proved challenging because genotype calling of genetic markers in triploids is not supported by standard software. Our aim was to develop a method that can be used for genotype calling of genetic markers in triploid individuals.ResultsAllele signals were produced for 381 triploid Atlantic salmon offspring using a 56 K Thermo Fisher GeneTitan genotyping platform. Genotypes were successfully called by applying finite normal mixture models to the (transformed) allele signals. Subsets of markers were filtered by quality control statistics for use with downstream analyses. The quality of the called genotypes was sufficient to allow for assignment of diploid parents to the triploid offspring and to discriminate between maternal and paternal parents from autosomal inheritance patterns. In addition, as the maternal inheritance in triploid offspring is identical to gynogenetic inheritance, the maternal recombination pattern for each chromosome could be mapped by using a similar approach as that used in gene-centromere mapping.ConclusionsWe show that calling of dense marker genotypes for triploid individuals is feasible. The resulting genotypes can be used in parentage assignment of triploid offspring to diploid parents, to discriminate between maternal and paternal parents using autosomal inheritance patterns, and to map the maternal recombination pattern using an approach similar to gene-centromere mapping. Genotyping of triploid individuals is important both for selective breeding programs and unravelling the underlying genetics of phenotypes recorded in triploids. In principle, the developed method can be used for genotype calling of other polyploid organisms.

Nuclear and Chloroplast Sequences Resolve the Enigmatic Origin of the Concord Grape.

Despite the commercial importance of the Concord grape, its origin has remained unresolved for over 150 years without a comprehensive phylogenetic analysis. In this study we aimed to reconstruct the evolutionary history of the Concord grape using sequence data from four nuclear markers (AT103, GAI1, PHYA, and SQD1), six plastid markers (matK, psbA-trnH, petN-trnC, ycf1, trnL-F, and trnS-G), and the plastid genome. We sampled extensively the Vitis species native to northeastern North America as well as representative species from Europe and Asia, including the commercially important Vitis vinifera (wine grape), a native European species with hermaphroditic flowers, and its wild progenitor, V. vinifera subsp. sylvestris. We also sequenced the plastid genome of one accession of the Concord grape and compared the plastid genome data to the recently published data set of Vitis plastomes. Phylogenetic analyses of the plastid and nuclear data using maximum likelihood and Bayesian inference support the hybrid origin of the Concord grape. The results clearly pinpoint the wine grape, V. vinifera, as the maternal donor and the fox grape, Vitis labrusca, which is common in northeastern North America, as the paternal donor. Moreover, we infer that the breeding history of the Concord grape must have involved the backcrossing of the F1 hybrid with the paternal parent V. labrusca. This backcrossing also explains the higher morphological similarity of the Concord grape to V. labrusca than to V. vinifera. This study provides concrete genetic evidence for the hybrid origin of a widespread Vitis cultivar and is, therefore, promising for similar future studies focused on resolving ambiguous origins of major crops or to create successful hybrid fruit crops.

Tetraploid Induction by Colchicine Treatment and Crossing with a Diploid Reveals Less-Seeded Fruit Production in Pointed Gourd (Trichosanthes dioica Roxb.).

Pointed gourd (Trichosanthes dioica Roxb.) (2n = 2x = 22) is a dioecious cucurbit vegetable and green fruit that is edible after cooking. Consumers prefer to consume seedless or less-seeded fruit because seeds are unpalatable due to their hard coats. Therefore, the cross compatibility between the diploid and induced tetraploid will be helpful for seedless or less-seeded fruit production. Thus, the present study was conducted using mature seeds that were immersed in 0.05%, 0.1%, and 0.5% colchicine for 24, 48, and 72 h to induce tetraploids. These tetraploids were used as parents (male or female) in the inter-ploidy and intra-ploidy crosses. A flow cytometric analysis confirmed the induction of three tetraploids at 0.5% colchicine for 48 and 72 h soaking periods. Among these, two (2) females and one (1) male were differentiated after flower initiation. Crossing between the tetraploid’s maternal and diploid paternal parent (4x × 2x), which were revealed to be compatible, resulted in a similar fruit set rate and shape as those of the diploid. In addition, a seed number of 4x × 2x produced fruits that were drastically reduced to 1.8 seeds per fruit, whereas the natural diploid fruits had 26.4 seeds per fruit. These findings suggest that colchicine-induced tetraploid females are important genetic resources for less-seeded fruit production. The genetic stability of tetraploid clones can easily and effectively be maintained by vine cutting for advanced uses.

Multifamily QTL analysis and comprehensive design of genotypes for high-quality soft wheat.

Milling properties and flour color are essential selection criteria in soft wheat breeding. However, high phenotypic screening costs restrict selection to relatively few breeding lines in late generations. To achieve marker-based selection of these traits in early generations, we performed genetic dissection of quality traits using three doubled haploid populations that shared the high-quality soft wheat variety Kitahonami as the paternal parent. An amplicon sequencing approach allowed effective construction of well-saturated linkage maps of the populations. Marker-based heritability estimates revealed that target quality traits had relatively high values, indicating the possibility of selection in early generations. Taking advantage of Chinese Spring reference sequences, joint linkage maps of the three populations were generated. Based on the maps, multifamily quantitative trait locus (QTL) analysis revealed a total of 86 QTLs for ten traits investigated. In terms of target quality traits, 12 QTLs were detected for flour yield, and 12 were detected for flour redness (a* value). Among these QTLs, six for flour yield and nine for flour a* were segregating in more than two populations. Some relationships among traits were explained by QTL collocations on chromosomes, especially group 7 chromosomes. Ten different ideotypes with various combinations of favorable alleles for the flour yield and flour a* QTLs were generated. Phenotypes of derivatives from these ideotypes were predicted to design ideal genotypes for high-quality wheat. Simulations revealed the possibility of breeding varieties with better quality than Kitahonami.

Genome-Wide Association Studies Reveal the Genetic Basis of Fertility Restoration of CMS-WA and CMS-HL in xian/indica and aus Accessions of Rice (Oryza sativa L.)

BackgroundWild-abortive cytoplasmic male sterility (CMS-WA) and Honglian CMS (CMS-HL) are the two main CMS types utilized in production of three-line hybrid rice in xian/indica (XI) rice. Dissection of the genetic basis of fertility restoration of CMS-WA and CMS-HL in the core germplasm population would provide valuable gene and material resources for development of three-line hybrid combinations.ResultsIn this study, two F1 populations with CMS-WA and CMS-HL background respectively were developed using 337 XI and aus accessions being paternal parents. Genome-wide association studies on three fertility-related traits of the two populations for two consecutive years revealed that both fertility restoration of CMS-WA and CMS-HL were controlled by a major locus and several minor loci respectively. The major locus for fertility restoration of CMS-WA was co-located with Rf4, and that for fertility restoration of CMS-HL was co-located with Rf5, which are cloned major restorer of fertility (Rf) genes. Furthermore, haplotype analysis of Rf4, Rf5 and Rf6, the three cloned major Rf genes, were conducted using the 337 paternal accessions. Four main haplotypes were identified for Rf4, and displayed different subgroup preferences. Two main haplotypes were identified for Rf5, and the functional type was carried by the majority of paternal accessions. In addition, eight haplotypes were identified for Rf6.ConclusionsHaplotype analysis of three Rf genes, Rf4, Rf5 and Rf6, could provide valuable sequence variations that can be utilized in marker-aided selection of corresponding genes in rice breeding. Meanwhile, fertility evaluation of 337 accessions under the background of CMS could provide material resources for development of maintainer lines and restorers.

Evidence of maternal effect on germination and vigor of sour passion fruit

Abstract The seminiferous propagation of Sour Passion Fruit (Passiflora edulis Sims) is the main kind of multiplication due to the ease formation of seedlings. However, the reduced number of productive and homogeneous cultivars reflects the need for genetic breeding. The objective of this study was to assess the maternal and reciprocal effects in vigor and germination of Sour Passion Fruit seeds. The experiment was conducted in a completely randomized design in the factorial scheme, with two structure (hybrid and reciprocal) and ten crosses with four replicates (50 seeds) in trays containing inert sand in germination chamber. Before sowing, it was obtained the weight of 100 seeds, and at 28 days germination percentage, emergence speed index, total seedlings length, shoot length and main root length, number of normal seedlings and dry mass per seedlings were evaluated. The reciprocal effects tell us which genotype is most promising when used as the female or male parent for the trait studied. It can be inferred that there is maternal effect influencing the weight of 100 seeds, emergence, emergence speed index and the number of normal seedlings. There was influence of the parent on the expression of traits in seeds of Sour Passion Fruit. It is important to define the paternal and maternal parent to obtain seeds with high germination potential.

Spray Chrysanthemum ‘Field Green’ with Yellow Green Petal, Single Type, and White Rust Resistance for Cut Flower

The chrysanthemum cultivar Field Green (Chrysanthemum x morifolium) was developed at the National Institute of Horticultural and Herbal Science, Rural Development Administration (RDA) in 2012. The cultivar Field Green was derived from the artificial crossing in 2008 between two spray chrysanthemum cultivars, Laque Roicks, a maternal p arent with y ellow single t ype flower, and F rill Green, a paternal parent with a green single type and white rust disease resistance. The vigorous plants with green petals and stable flower shapes were selected in 2009. After an evaluation of the characteristics, including shading culture in summer and retarding culture in spring and consecutive selections from 2010 to 2012, the final selection was made. The flowering time of Field Green was October 26 in a natural day length, and year-round production was possible by day-length treatment. This cultivar has single-type flowers with bright green ray florets and green disc florets. The number of ray florets is 18.8, and the flower diameter is 7.1 cm. The growth of the plant is vigorous, with a plant height of 130 cm. Field Green is highly resistant to white rust disease, and vase life is about 20 days in autumn. Number 2013-153 was applied to Field Green on February 20, 2013 for variety protection; its plant variety protection rights were then registered (No. 4839) on April 2, 2014 at the Korea Seed and Variety Service.

Paternal Contribution to Banana (Musa sapientum L.) & Plantain (Musa paradisiaca L.) Progenies & Progeny Ploidy Composition in a Polycross Mating System Using RAPD & Flow Cytometry

Aims: A 4x – 2x polycross mating design of 4 tetraploid female parents was established to determine paternal contributions of 3 diploid male parents to resulting progenies, their ploidy composition and genetic diversity of synthetic hybrids.
 Study Design: The polycross mating design comprised 2 blocks having both maternal and paternal selections, with seed parents replicated at 12 plants per clone. Each crossing block had 31 plants of each of the three male parents.
 Place and Duration of Study: International Institute of Tropical Agriculture (IITA) High Rainfall Station, Onne (4º51’N, 7º03’E, 10 m above sea level), Rivers State, South-South Nigeria for a period of 24 months.
 Methodology: At maturity of maternal parents (TMPx 2796-5; TMPx 1658-4; TMPx 5511-2; and TMPx 7152-2), fruit bunches were harvested, ripened and the seeds extracted. Hard seeds obtained were germinated in vivo in seed trays and emerging seedlings transplanted to perforated nursery bags. At 12 weeks, DNA was extracted from candle leaf for RAPD analysis of 80 progenies and the 3 pollen parents. Ploidy status of progenies was determined using flow cytometry method.
 Results: There was significant unequal paternal contribution to Musa polycross progenies with 3 maternal parents; TMPx 2796-5, TMPx 5511-2, and TMPx 1658-4. Two of the 3 paternal parents had progenies with all 4 maternal parents while TMB2x 5105-1 did not have any progeny with TMPx 2796-5. Progenies exhibited 4 ploidy levels with frequency differing with each female parent: TMPx 7152-2 produced 100% 3x progeny; TMPx 5511-2, 63% 3x and 37% 2x; TMPx 2796-5, 91% 3x and 9% 2x and TMPx 1658-4, 82% 3x, 9% 2x, 6% 4x and 3% 5x. The 5x progeny was recorded in the first ratoon crop. The second ratoon crop had only triploids.
 Conclusion: The high frequency of 3x progenies from all maternal types in this study, suggests the effectiveness of the polycross mating design in Musa improvement.

Fitness of F1 hybrids between stacked transgenic rice T1c-19 with cry1C*/bar genes and weedy rice

Compared to single-trait transgenic crops, stacked transgenic plants may be more prone to become weedy, and transgene flow from stacked transgenic plants to weedy relatives may pose a potential environmental risk because these hybrids could be more advantageous under specific environmental conditions. Evaluation of the potential environmental risk caused by stacked transgenes is essential for assessing the environmental consequences caused by crop-weed transgene flow. The agronomic performance of fitness-related traits was assessed in F1+ (transgene positive) hybrids (using the transgenic line T1c-19 as the paternal parent) in monoculture and mixed planting under presence or absence glufosinate pressure in the presence or absence of natural insect pressure and then compared with the performance of F1– (transgene negative) hybrids (using the non-transgenic line Minghui 63 (MH63) as the paternal parent) and their weedy rice counterparts. The results demonstrated that compared with the F1– hybrids and weedy rice counterparts, the F1+ hybrid presented higher performance (P<0.05) or non-significant changes (P>0.05) under natural insect pressure, respectively, lower performance (P<0.05) or non-significant changes (P>0.05) in the absence of insect pressure in monoculture planting, respectively. And compared to weedy rice counterparts, the F1+ hybrid presented higher performance (P<0.05) or non-significant changes (P>0.05) in the presence or absence of insect pressure in mixed planting, respectively. The F1+ hybrids presented non-significant changes (P>0.05) under the presence or absence glufosinate pressure under insect or non-insect pressure in monoculture planting. The all F1+ hybrids and two of three F1– hybrids had significantly lower (P<0.05) seed shattering than the weedy rice counterparts. The potential risk of gene flow from T1c-19 to weedy rice should be prevented due to the greater fitness advantage of F1 hybrids in the majority of cases.

Selection estimation of red currant hybrid family ‘Belaya Potapenko’ x SS 1426-21-80

Relevance.One of the priority trends in berry crop breeding is to create highly adaptive and resistant to biotic and abiotic environmental factors varieties with high commodity and consumer quality of berries, not inferior to the best Western European varieties.Material and methods.The research was conducted in 2017-2018 at VNIISPK (Orel) on the selection plot of red currants, planted in 2012, with a planting scheme 2.8 x 0.8 m. The research object was the selection red currant family 2466 (♀Belaya Potapenko x ♂SS 1426-21-80) of VNIISPK breeding in the amount of 66 hybrid seedlings. The parent forms of this family were selected as sources of valuable economical and breeding characters. The variety Belaya Potapenko has a dessert taste of berries, and the selected seedling 1426-21-80 was taken due to its productivity and long racemes. The economical and biological characters of the hybrid seedlings were studied according to the “Program and methods of fruit, berry and nut crops variety investigation”, section “Currants, gooseberry and their hybrids” (1999).Results.The progeny of the crossing combination Belaya Potapenko x SS 1426-21-80 is characterized by high adaptability to soil and climatic conditions of cultivation that provides good development of the seedlings and their high productivity. When crossing white-fruit Belaya Potapenko with redfruit SS 1426-21-80, seedlings with white berries are absent in the offspring, which indicates that the paternal original form is homozygous for the dominant gene that controls the red color of the berries. Hybridological analysis showed that with medium weight of berries of parental forms, the manifestation of this trait in the offspring increased, the share of large-fruited seedlings was 18-37%, depending on the year of the study. The taste estimation of the off-spring of this family showed that a great amount of the seedlings had an intermediate sweet and sour taste, part of hybrids inherited sour taste from the paternal original parent. The hybrid family is valuable for the output of highly productive large-fruited seedlings with long racemes. Re-hybridization of the best seedlings with sources of high taste of berries is necessary to improve the taste.

Genetic mapping of leaf-related traits in autotetraploid alfalfa (Medicago sativa L.)

Understanding the genetic architecture of leaf-related traits is important for improving alfalfa yield. Leaf size has a great influence on the protein content and yield for alfalfa. In this study, a low-yielding precocious alfalfa individual (paternal parent) and a high-yielding late-maturing alfalfa individual (maternal parent) were used to build a hybrid F1 population of 149 individuals. The linkage map was constructed using simple sequence repeat and single nucleotide polymorphism markers, and quantitative trait loci (QTL) for leaf length, leaf width, and leaf area were mapped using 3 years phenotypic data. We identified a total of 60 QTLs associated with leaf size. These QTLs were located on chromosomes 1 to 8, and the percent of phenotypic variation explained by QTL ranged from 2.97% to 18.78%. There were 13 QTLs explain more than 10% of phenotypic variation, most of which represent novel loci controlling leaf traits that have not been found in previous studies. The nearest markers of QTL may be used in marker-assisted selection and breeding alfalfa new varieties with high yield.

Creation of an avocado unambiguous genotype SNP database for germplasm curation and as an aid to breeders

Avocado (Persea americana) is an important tropical and subtropical fruit tree crop. Traditional tree breeding programs face the challenges of long generation times and significant expense in land and personnel resources. Avocado selection and breeding can be more efficient and less expensive through the development and application of molecular markers. A total of 1524 individuals were genotyped with 384 SNPs creating the largest SNP genotype database for avocado. These individuals correspond to four extensive germplasm collections including two housed in Florida and two in California. In addition, hybrids and selections from two rootstock breeding programs have been genotyped. Genotype data were analyzed using an affinity propagation method to define 155 groups. The 384 SNP markers provided accurate genotype data for individuals from different Persea species as well as half-siblings. Therefore, the majority of the genetic diversity of the avocado germplasm and related species that were genotyped has been captured. A simple visual method can also be used to identify self-pollinated individuals among the half-siblings of known maternal parents and, in some cases, to infer likely candidates for the paternal parent. Finally, this dataset is unambiguous so breeders can determine the genetic diversity of their breeding stock to optimize avocado breeding and selection programs by identifying outcrossed individuals at the seedling stage, thus increasing the efficiency of avocado genetic improvement.

High Density Genetic Maps of Seashore Paspalum Using Genotyping-By-Sequencing and Their Relationship to The Sorghum Bicolor Genome

As a step towards trait mapping in the halophyte seashore paspalum (Paspalum vaginatum Sw.), we developed an F1 mapping population from a cross between two genetically diverse and heterozygous accessions, 509022 and HI33. Progeny were genotyped using a genotyping-by-sequencing (GBS) approach and sequence reads were analyzed for single nucleotide polymorphisms (SNPs) using the UGbS-Flex pipeline. More markers were identified that segregated in the maternal parent (HA maps) compared to the paternal parent (AH maps), suggesting that 509022 had overall higher levels of heterozygosity than HI33. We also generated maps that consisted of markers that were heterozygous in both parents (HH maps). The AH, HA and HH maps each comprised more than 1000 markers. Markers formed 10 linkage groups, corresponding to the ten seashore paspalum chromosomes. Comparative analyses showed that each seashore paspalum chromosome was syntenic to and highly colinear with a single sorghum chromosome. Four inversions were identified, two of which were sorghum-specific while the other two were likely specific to seashore paspalum. These high-density maps are the first available genetic maps for seashore paspalum. The maps will provide a valuable tool for plant breeders and others in the Paspalum community to identify traits of interest, including salt tolerance.

Interspecies hybrids of Panax ginseng Meyer new line 0837 and Panax quinquefolius generated superior F1 hybrids with greater biomass and ginsenoside contents

Panax ginseng and Panax quinquefolius are important herbs with similar benefits and medicinal properties. Both possess ginsenosides, the pharmacologically active components, abundantly in their roots. In an attempt to establish ginseng cultivars with improved agronomical characters and higher ginsenoside content, reciprocal interspecific hybrids were generated by artificial pollination of emasculated flowers. Three elite cultivars of P. ginseng, types Jakyung, Chungkyung, and Hwangsook, and two new lines, 0837 and 0702, were used to assess interspecific hybrid potential. Among F1 reciprocal hybrids generated using line 0837 as either the maternal or paternal parent showed excellent agronomical traits and hybrid vigor. They showed strong root phenotypes with many lateral and fine roots resulting in 10 to 20% higher ginsenoside content compared to the parental lines. Among the major ginsenosides, pharmacologically active Re, Rb1, Rb2, and F1 were enriched. They accounted for 70% of the protopanaxadiol ginsenosides in 0837/Pq and Pq/0837 crosses, displaying strong maternal dominance. Thus, based on our results, we conclude that P. ginseng line 0837 is superior compared to already existing lines for performing interspecific hybridization with promising outcomes in root quality and ginsenoside content.

Paternally Acting Canonical RNA-Directed DNA Methylation Pathway Genes Sensitize Arabidopsis Endosperm to Paternal Genome Dosage.

Seed development is sensitive to parental dosage, with excess maternal or paternal genomes creating reciprocal phenotypes. Paternal genomic excess frequently results in extensive endosperm proliferation without cellularization and seed abortion. We previously showed that loss of the RNA polymerase IV gene NUCLEAR RNA POLYMERASE D1 (NRPD1) in tetraploid fathers represses seed abortion in paternal excess crosses. Here, we show genetically that RNA-directed DNA methylation (RdDM) pathway activity in the paternal parent is sufficient to determine the viability of paternal excess Arabidopsis (Arabidopsis thaliana) seeds. We compared transcriptomes, DNA methylation, and small RNAs from the endosperm of seeds from balanced crosses (diploid × diploid) and lethal (diploid × tetraploid) and viable paternal excess crosses (diploid × tetraploid nrpd1). Endosperms from both lethal and viable paternal excess seeds share widespread transcriptional and DNA methylation changes at genes and transposable elements. Interploidy seed abortion is thus unlikely to be caused by transposable elements or imprinted gene misregulation, and its repression by the loss of paternal RdDM is associated with only modest gene expression changes. Finally, using allele-specific transcription data, we present evidence for a transcriptional buffering system that increases the expression of maternal alleles and represses paternal alleles in response to excess paternal genomic dosage. These findings prompt reconsideration of models for dosage sensitivity in endosperm.

Mating barriers between genetically divergent strains of the parasitic nematode Haemonchus contortus suggest incipient speciation

Haemonchus contortus, in common with many nematode species, has extremely high levels of genetic variation within and between field populations derived from distant geographical locations. MHco10(CAVR), MHco3(ISE) and MHco4(WRS) are genetically divergent H. contortus strains, originally derived from Australia, Kenya and South Africa, respectively, that have been maintained by numerous rounds of in vivo experimental infection of sheep. In order to explore potential pre-zygotic competition or post-zygotic incompatibility between the strains, we have investigated the ability of MHco10(CAVR) to interbreed with either MHco3(ISE) or MHco4(WRS) during dual strain co-infections. Sheep were experimentally co-infected with 4000 infective larvae (L3) per os of the MHco10(CAVR) strain and an equal number of either the MHco3(ISE) or the MHco4(WRS) strain L3. The adult worm establishement rates and the proportions of F1 progeny resulting from intra- and inter-strain mating events were determined by admixture analysis of microsatellite multi-locus genotypes. Although there was no difference in adult worm establishment rates, the proportions of F1 progeny of both the MHco10(CAVR) × MHco3(ISE) and MHco10(CAVR) × MHco4(WRS) dual strain co-infections departed from Mendelian expectations. The proportions of inter-strain hybrid F1 progeny were lower than the expected 50%, suggesting either pre-zygotic competition or post-zygotic incompatibility between the co-infecting strains. To investigate this further, both eggs and hatched L1 of broods from single adult female worms recovered from each dual co-infection were genotyped. Unhatched eggs from the broods revealed no inter-strain hybrid genotype deficit, suggesting there is no pre-zygotic competition between the strains. In contrast, there was a deficit in L1 inter-strain hybrid genotypes in the broods derived from MHco3(ISE) or MHco4(WRS) maternal parents, but not from MHco10(CAVR) maternal parents. This suggests that hybrid progeny of MHco10(CAVR) paternal parents have reduced post-zygotic development and/or viability consistent with incipient speciation of the MHco10(CAVR) strain. The presence of mating barriers between allopatric H. contortus strains has important implications for parasite ecology, including the ability of newly introduced anthelmintic-resistant parasite populations to compete and interbreed with populations already established in a region.

Estimation of genetic diversity and relatedness in a mango germplasm collection using SNP markers and a simplified visual analysis method

Mango is a globally important tropical fruit but lacks genomic tools to support cultivar identification and to enable breeding efforts. Assessing the genetic diversity and relatedness of mango germplasm is essential for identifying genetically distant parents with favorable agronomic traits to produce hybrid populations enabling selection of improved cultivars. We thus genotyped 1915 mango accessions from the United States, Senegal, Thailand, and Australia with 272 single nucleotide polymorphism (SNP) markers identifying over 520,000 genotypes. These accessions represent the available diversity from both public and private germplasm collections in these countries, as well as accessions from smaller international collections. The study included Mangifera indica, other Mangifera species, and accessions from half sibling populations. Genotype data were analyzed using an affinity propagation method to define 258 groups. Using a simple visual method, no more than 30 SNPs are needed to distinguish a single cultivar of interest from all other cultivars in the dataset enabling the accurate identification of important commercial cultivars. As these SNP markers provided accurate genotype data for accessions from different genera as well as half siblings, the majority of the genetic diversity of the mango germplasm and related species that were genotyped has been captured. The dataset contains a large collection of open-pollinated half siblings from known maternal parents. A simple visual method can also be used to identify self-pollinated individuals among the half siblings of known maternal parents and, in some cases, to infer likely candidates for the paternal parent. Identification of self-pollinated individuals is particularly important in terms of selection of improved cultivars, as due to high levels of heterozygosity, self-pollinated progeny are likely to uncover deleterious recessive alleles. Genotyping of progeny at the seedling stage and removal of self-pollinated progeny can increase the efficiency and decrease the costs of selection of improved cultivars from open-pollinated populations.