Introgression Of Germplasm Research Articles

Introgression of Asian germplasm into natural populations of Castanea sativa Mill. in southern Europe

Introgression of Asian germplasm into natural populations of <i>Castanea sativa</i> Mill. in southern Europe

Analysis of population structure and genetic diversity in a Southern African soybean collection based on single nucleotide polymorphism markers

Soybean is an emerging strategic crop for nutrition, food security, and livestock feed in Africa, but improvement of its productivity is hampered by low genetic diversity. There is need for broadening the tropical germplasm base through incorporation and introgression of temperate germplasm in Southern Africa breeding programs. Therefore, this study was conducted to determine the population structure and molecular diversity among 180 temperate and 30 tropical soybean accessions using single nucleotide polymorphism (SNP) markers. The results revealed very low levels of molecular diversity among the 210 lines with implications for the breeding strategy. Low fixation index (FST) value of 0.06 was observed, indicating low genetic differences among populations. This suggests high genetic exchange among different lines due to global germplasm sharing. Inference based on three tools, such as the Evanno method, silhouette plots and UPMGA phylogenetic tree showed the existence of three sub-populations. The UPMGA tree showed that the first sub-cluster is composed of three genotypes, the second cluster has two genotypes, while the rest of the genotypes constituted the third cluster. The third cluster revealed low variation among most genotypes. Negligible differences were observed among some of the lines, such as Tachiyukata and Yougestu, indicating sharing of common parental backgrounds. However large phenotypic differences were observed among the accessions suggesting that there is potential for their utilization in the breeding programs. Rapid phenotyping revealed grain yield potential ranging from one to five tons per hectare for the 200 non-genetically modified accessions. Findings from this study will inform the crossing strategy for the subtropical soybean breeding programs. Innovation strategies for improving genetic variability in the germplasm collection, such as investments in pre-breeding, increasing the geographic sources of introductions and exploitation of mutation breeding would be recommended to enhance genetic gain.

Molecular evidence of introgression of Asian germplasm into a natural Castanea sativa forest in Spain

Abstract Evidence has been documented in Europe of introgression, the transfer of genetic material, between Asian chestnut species (Castanea crenata and C. mollissima) and the native C. sativa through spontaneous hybridization and subsequent backcrossing. However, the extent of this introgression has not been monitored in a particular forest stand or in adult and juvenile trees simultaneously. We assessed introgression in a natural C. sativa forest in northwest Spain and developed a reliable method to detect the presence of Asian germplasm of Castanea spp. A total of 34 adult trees and 42 saplings were genotyped at 13 SSRs in a forest where ink-disease-resistant C. crenata and C. mollissima seedlings had been planted in the 1940s. The 13 SSR loci selected were highly polymorphic and 115 different alleles were detected for the individuals sampled. Bayesian clustering identified two groups for C. sativa and one group each for C. mollissima and C. crenata. Within the forest, 70.6 per cent of adults and 28.6 per cent of juveniles were classified as pure C. sativa. Most juveniles were C. sativa × C. crenata (&amp;gt;40 per cent) and ca. 10 per cent were C. crenata × C. mollissima hybrids. Six new alleles private to C. crenata are reported here. The study quantifies, for the first time in Europe, introgression of Asian germplasm into a natural C. sativa forest. It also examines the extent of introgression in offspring and provides a method to detect exotic germplasm in C. sativa forests. We discuss why the forest studied may benefit from transfer of alleles involved in ink-disease resistance and why introgression will be detrimental to drought tolerance in offspring.

Elevated CO2 differentially affects the properties of grain from wild and domesticated rice

Interspecific germplasm from wild species of Oryza will be increasingly applied to breeding programs over the coming decades. However, the concurrent impact of rising atmospheric CO2 concentrations (atm-CO2) on grain properties is unknown. Wild accessions of Australian native rice species (Oryza australiensis and O. meridionalis) and the local cultivar (O. sativa cv. Doongara) were grown to maturity in glasshouses at ambient (400 ppm; aCO2) and elevated (700 ppm; eCO2) atm-CO2 and physicochemical properties of the grains were compared. Seed length (Sl), seed width (Sw) and 1000-seed weight (TSW) were higher at eCO2 than aCO2, while nitrogen content (N) and apparent amylose content (AC) were not significantly changed, irrespective of genotype. Rapid viscosity analyser (RVA) profiles revealed increased peak viscosity (PV) for rice under eCO2, indicating differences in starch gelatinization. However, final viscosity (FV) increased in the wild rices in eCO2, whereas it decreased in Doongara. Increases in PV were accompanied by lower estimates of protein contents (PC) at eCO2 in all species. When AgNO3 was excluded from the RVA, it became apparent that its presence had enhanced the effects of eCO2 on flour pasting properties through inhibition of α-amylase activity of the flour. Our results suggest that grain morphology and pasting properties are differently affected by eCO2 in the wild rices compared with cultivated rice. These data will inform the breeding criteria for rice grain properties and inform the introgression of wild germplasm.

Evaluating Wild Germplasm Introgression into Autotetraploid Blueberry

Wild germplasm can be classified as the raw material essential for crop improvement. Introgression of wild germplasm is normally used in breeding to increase crop quality or resilience to evolving biotic and abiotic threats. Here, we explore the potential of introgressing Vaccinium elliottii into commercial blueberry germplasm. Vaccinium elliottii is a wild diploid blueberry species endemic to the southeastern United States that possesses highly desirable and economically important traits for blueberry breeding such as: short bloom to ripe period, adaptation to upland sandy soils, disease resistance, firmness, and pleasant flavor. To examine the potential of hybridization, we evaluated populations of interspecific hybrids across multiple stages of breeding (i.e., F1, F2, and backcrosses) in two crop seasons. We used our extensive pedigree data to generate breeding values for pre-breeding blueberry hybrid populations. Hybrid performance was evaluated considering fitness (i.e., plant vigor and plant height) in addition to evaluating six fruit-quality and marketable-related traits (i.e., size, firmness, acidity, soluble solids, weight, and yield). Overall, F2 and backcrosses rapidly achieved market thresholds, presenting values not significantly different from commercial blueberry germplasm. Our results confirmed the potential of exploiting the high genetic variability contained in V. elliottii for interspecific hybridization. Additionally, we developed germplasm resources that can be further evaluated and utilized in the breeding process, advancing selections for fruit quality and environmental adaptation.

Assessment of genetic gains from introgression of temperate genes into tropical elite maize inbred lines: I. performance per se

There is very limited information on genetic gains and improvement of maize inbred line performance per se that has been attained through introgression of temperate germplasm into tropical maize germplasm to enhance adaptability in target environments. The objective of this study was to determine the genetic gains for grain yield and its components achieved by introgression of temperate germplasm into tropical elite maize inbred lines. A total of 123 maize inbred lines comprising of 76 introgressed inbred lines, 21 tropical inbred lines (negative controls) and 26 temperate inbred lines (positive controls) were evaluated in an augmented design at four sites. The strategy was effective and successful to enhance grain yield, in particular, ear prolificacy. Positive genetic gains were realised for grain yield (5%) and ear prolificacy (46%) relative to the population and mean of checks. Selection for plant and ear height, root and stalk lodging had gains ranging from 2 to 11%. However, traits such as anthesis and silking days and grain moisture content at harvest had low gains. Introgressed inbred line performance per se was impressive because new inbred lines with potential for commercial production were obtained. Inbred line 71-DMLF7_88 showed combined early physiological maturity, high ear prolificacy and grain yield potential that were at par with the mean of the temperate checks. Thus, indicating an improvement in the agronomic performance of the improved tropical based material that normally performs below temperate checks in South African warm temperate environments. In conclusion, introgression of temperate germplasm into tropical elite inbred lines was effective in improving adaptation in warm temperate environments.

Agromorphological Characterization of Introgression Lines Derived from Wild and Exotic Sorghum Germplasm to Climate Change Challenges

Sorghum (Sorghum bicolor (L.) Moench) is vitally important for food security in semi-arid West Africa. The introgression of wild- and high transpiration efficiency genotypes may contribute genes for abiotic stress tolerance or novel traits. Characterizing the introgressed lines can help researchers in the process of varietal improvement. The objectives of this study are (i) To learn if introgression of wild sorghum (CWR) and high transpiration efficiency (HTE) lines into a very early maturing (photoperiod insensitive) local land-race variety can create useful variation for grain yield in drought-prone Sahelian environments, (ii) To determine if grain yield advantages (and putative drought tolerance traits) obtained from introgression of CWR and HTE germplasm are expressed differently in moderately to highly moisture-limited environments, and (iii) To understand the relationship between putative drought tolerance traits. These populations were developed from crosses between the CSM63E (Jakumbe, a high grains quality variety) and two wild parents (accessions) and five high transpiration efficiency (TE) sorghum accessions. Phenotyping was conducted using an alpha lattice design with three replications in two environments for agronomic traits (grain yield and components), flowering time and physiological traits (stay-green, chlorophyll content and lodging). A total of 669 BC1F5 progenies were developed. Genetic variation for grain yield and putative drought tolerant traits were evaluated. Both populations derived from wild parents exhibited in Cinzana a grain yield (>300 g/m2) greater than CSM63E (245 g/m2). In Bema, more than 75% of the progenies of all populations indicated a chlorophyll content at physiological maturity (>30 SPAD) higher than CSM63E (20 SPAD) chlorophyll content. The estimated broad sense heritability was generally high (≥0.50) for all traits. The results also showed a very significant interaction between genotype and environment for grain yield, flowering time, chlorophyll content, stay green and lodging. There was a strong correlation between stay green and chlorophyll content (0.60) on the one hand and between stay green and lodging (0.48) on the other. This great variability could help improve the grain yield of sorghum for farmers in the Sahelian zone.

Effects of drought on agronomic and fiber quality in an introgressed backcross inbred line population of Upland cotton under field conditions

Upland cotton (Gossypium hirsutum) is the most important fiber crop and an important oilseed crop in the world. Developing drought tolerant cultivars is important to sustainable cotton production in arid and semi-arid regions. However, there is a lack of information on genetic variation for drought tolerance in breeding populations. In this study, a backcross inbred line (BIL) Upland population with germplasm introgression from a more drought-tolerant American Pima cotton (G. barbadense) parent was evaluated in multiple field environments under well-watered (WW) and water-limited (WL) conditions at the flowering stage. Drought at the flowering stage reduced seedcotton yield (SCY), lint yield (LY), boll weight (BW), fiber length (FL), and fiber strength (STR) but increased lint percentage (LP), micronaire (MIC), neps per size, nep per gram, seedcoat nep size, and seed coat fragment count by gram. Significant genetic differences in the BIL population were detected for most agronomic and fiber quality traits and drought susceptibility index (DSI) for these traits. DSI of SCY and LY ranged from 0.01 to 1.5 and 0.1–1.45, respectively, reflecting the tolerance level of the BILs under WL conditions. The broad-sense heritability estimates were moderate for most agronomic traits and moderate to high for most fiber quality traits. Results indicated that highly positive correlation was detected for agronomic and fiber quality traits between WW and WL conditions, with the highest correlations for SCY, LY, UHM, SCY, and MIC. Promising BILs with drought tolerance were identified. This study has provided a line of evidence that field drought tolerance was transferred from the more drought tolerant Pima line to Upland cotton.

Genetic Relationships Among Portuguese Cultivated and Wild Vitis vinifera L. Germplasm.

The domesticated grapevine spread along the Mediterranean basin from the primary Near East domestication area, where the greatest genetic diversity is found in its ancestor, the wild vine populations. Portuguese wild populations are on the southwestern fringe of the distribution of the Vitis vinifera L. ssp. sylvestris (C.C. Gmel.) Hegi in Europe. During the last Glacial Period they became isolated from the previous continuum that had been the territory of wild vine populations. Archaeological remains of domesticated vinifera grapevines in Portugal date back from 795 Before Common Era (BCE) in the lower Tagus river basin. In this work, 258 Portuguese vinifera varieties and sylvestris plants were characterized using 261 single nucleotide polymorphism (SNP) markers. The study of the genetic diversity of this local germplasm, its population structure and kinship, all framed in their historical and geographical backgrounds, revealed a complex network of first-degree relationships, where only Iberian varieties are involved. Some Iberian genotypes, like Alfrocheiro (Bruñal, in Spain), Sarigo (Cayetana Blanca), Mourisco Branco (Hebén), Amaral (Caiño Bravo), and Marufo (Moravia Dulce) are ancestors of a considerable fraction of all the autochthonous analyzed varieties. A part of the diversity developed was mostly local in some cases as shown by the closeness of several varieties (Vinhos Verdes) to the wild cluster in different analyses. Besides, several evidences of introgression of domesticated germplasm into wild vines was found, substantiating the high risk of genetic contamination of the sylvestris subspecies. All these findings together to the known matching between the wild maternal lineage of the Iberian Peninsula and an important number of Portuguese grapevine varieties (chlorotype A), point out that some of these varieties derive, directly or indirectly, from originally local wild populations, supporting the possible occurrence of secondary events of local domestication, or, at least, of an introgression process of wild into cultivated grapevines.

Predicted genetic gains from introgressing chromosome segments from exotic germplasm into an elite soybean cultivar.

To improve an elite soybean line, introgress longer chromosome segments instead of QTL alleles from exotic germplasm. Broadening the diversity of cultivated soybean [Glycine max (L.) Merrill] through introgression of exotic germplasm has been difficult. Our objectives were to (1) determine if introgressing specific chromosome segments (instead of quantitative trait locus alleles) from exotic soybean germplasm has potential for improving an elite cultivar, and (2) identify strategies to introgress and pyramid exotic chromosome segments into an elite cultivar. We estimated genomewide marker effects for yield and other traits in seven crosses between the elite line IA3023 and seven soybean plant introductions (PIs). We then predicted genetic gains from having ≤ 2 targeted recombinations per linkage group. When introgression was modeled for yield while controlling maturity in the seven PI × IA3023 populations, the predicted yield was 8-25% over the yield of IA3023. Correlated changes in maturity, seed traits, lodging, and plant height were generally small but were in the favorable direction. In contrast, selecting the best recombinant inbred (without targeted recombination) in each of the PI × IA3023 populations led to negative or minimal yield gains over IA3023. In one PI × IA3023 population, introgressing and pyramiding only two linkage groups from recombinant inbreds into IA3023 was predicted to achieve an 8% yield gain over IA3023 without sacrificing the performance for other traits. The probability of inheriting intact chromosomes was high enough to allow introgression and pyramiding of chromosome segments in 5-6 generations. Overall, our study suggested that introgressing specific chromosome segments is an effective way to introduce exotic soybean germplasm into an elite cultivar.

Genetic Variation and Path Coefficient Analysis of Introgressed Maize Inbred Lines for Economic Traits

Knowledge of the effects of introgressing temperate maize germplasm in tropical elite inbred lines on genetic variation and relationship between grain yield and its components is limited. In this study, the objective was to evaluate introgressed maize inbred lines for selected economic traits. Field evaluation was carried out on 122 inbred lines comprising sets of introgressed lines from three selection environments, parental inbred lines and two common checks. Genetic variation was significant (P &amp;lt; 0.05) for all the major economic traits among inbred lines within and across sets. Heritability estimates ranged from low (0.21%) to high (91%) for stalk lodging and silking days, respectively. Comparison of means of inbred lines sets illustrated that environmental effect had influence on grain yield of introgressed lines. Grain yield and ear prolificacy performance across sets also illustrated that introgression of temperate germplasm in tropical elite inbred lines was effective. Spearman&amp;rsquo;s rank correlation analysis on grain yield and ear prolificacy highlighted correlation between selection environments. Correlation among traits demonstrated that grain yield had significant (P &amp;lt; 0.05) positive correlation with plant and ear aspects, plant height, root and stalk lodging, ear prolificacy and grain moisture content at harvest. Further, decomposing of correlation using path coefficient analysis showed significant (P &amp;lt; 0.05), and moderate direct effects of ear prolificacy and plant height on grain yield; indicating that these traits had the highest contribution towards grain yield. Generally indirect effects of secondary traits on grain yield potential of inbred lines was negligible. Therefore, direct selection of plant height and ear prolificacy will be emphasised during introgression of temperate germplasm in tropical elite inbred lines.

Recombination between homoeologous chromosomes induced in durum wheat by the Aegilops speltoides Su1-Ph1 suppressor

Su1-Ph1, which we previously introgressed into wheat from Aegilops speltoides, is a potent suppressor of Ph1 and a valuable tool for gene introgression in tetraploid wheat. We previously introgressed Su1-Ph1, a suppressor of the wheat Ph1 gene, from Aegilops speltoides into durum wheat cv Langdon (LDN). Here, we evaluated the utility of the introgressed suppressor for inducing introgression of alien germplasm into durum wheat. We built LDN plants heterozygous for Su1-Ph1 that simultaneously contained a single LDN chromosome 5B and a single Ae. searsii chromosome 5Sse, which targeted them for recombination. We genotyped 28 BC1F1 and 84 F2 progeny with the wheat 90-K Illumina single-nucleotide polymorphism assay and detected extensive recombination between the two chromosomes, which we confirmed by non-denaturing fluorescence in situ hybridization (ND-FISH). We constructed BC1F1 and F2 genetic maps that were 65.31 and 63.71cM long, respectively. Recombination rates between the 5B and 5Sse chromosomes were double the expected rate computed from their meiotic pairing, which we attributed to selection against aneuploid gametes. Recombination rate between 5B and 5Sse was depressed compared to that between 5B chromosomes in the proximal region of the long arm. We integrated ND-FISH signals into the genetic map and constructed a physical map, which we used to map a 172,188,453-bp Ph1 region. Despite the location of the region in a low-recombination region of the 5B chromosome, we detected three crossovers in it. Our data show that Su1-Ph1 is a valuable tool for gene introgression and gene mapping based on recombination between homoeologous chromosomes in wheat.

Introgression of wild germplasm into cultivated ornamental plants

Introgression of genes from one species into another is a major factor in plant evolution in nature. In the development of many commercially produced ornamental species, both natural and artificial introgression have played a role. When initiating a breeding programme in a new crop, basic information on the reproductive biology, pollination, and hybridization process has to be collected. Morphological descriptions of the available germplasm together with knowledge on the genetic relationships and cytological information (chromosome numbers and genome sizes) of the different accessions are essential before starting the breeding. However, when interspecific or intergeneric crosses are made, breeders are frequently confronted with numerous problems that hamper success. Bottlenecks can be either prezygotic or postzygotic. Several techniques, among others chromosome doubling, embryo rescue and in-vitro pollination, are available to overcome these problems.

Agronomic Traits in Durum Wheat Germplasm Possessing Puroindoline Genes

Core Ideas Durum wheat is an underutilized crop due to it hard kernel texture; soft kernel durum removes this limitation. Initial soft kernel durum lines show favorable agronomic performance, including grain yield and pest resistance. Soft durum lines show strong potential for future growth in the Pacific Northwest. ABSTRACTDurum wheat (Triticum turgidum subsp. durum) represents only 5% of global wheat production. Durum production is limited by its very hard kernel texture, which requires specialized milling and limits end‐product utilization. However, soft kernel durum wheat was recently developed to remove these constraints, but it has not until now been examined for its agronomic potential and pest resistance, which were the focus of this study. The soft durum lines were compared with two commercial hard red spring wheat varieties, Buck Pronto and Alum. Soft durum lines were relatively competitive for grain yield (i.e., &gt;90%) with Buck Pronto at 16 of 34 locations. Increasing seeding rate did not increase grain yield of soft durum. The soft durum lines showed no tolerance of acid soils/Al, but exhibited moderate‐to‐strong resistance to stripe rust (caused by Puccinia striiformis f. sp. tritici). Good resistance to stem rust (caused by Puccinia graminis f. sp. tritici) and near complete resistance to dwarf bunt (caused by Tilletia controversa) were observed. Resistance to Hessian fly (Mayetiola destructor) was observed in some of the plants, with three of the durum lines showing a larger proportion of resistant plants. Varying levels of resistance to cereal cyst nematode (Heteroderma filipjevi) were recorded, with some lines highly resistant. These studies show that there is good agronomic potential in the current soft durum lines for moderate yield and good pest resistance. Further breeding efforts and germplasm introgression will likely improve the competitiveness of soft durum wheat with currently grown hard red spring wheat.

QTL analysis of cotton fiber length in advanced backcross populations derived from a cross between Gossypium hirsutum and G. mustelinum

QTLs for fiber length mapped in three generations of advanced backcross populations derived from crossing Gossypium hirsutum and Gossypium mustelinum showed opportunities to improve elite cottons by introgression from wild relatives. The molecular basis of cotton fiber length in crosses between Gossypium hirsutum and Gossypium mustelinum was dissected using 21 BC3F2 and 12 corresponding BC3F2:3 and BC3F2:4 families. Sixty-five quantitative trait loci (QTLs) were detected by one-way analysis of variance. The QTL numbers detected for upper-half mean length (UHM), fiber uniformity index (UI), and short fiber content (SFC) were 19, 20, and 26 respectively. Twenty-three of the 65 QTLs could be detected at least twice near adjacent markers in the same family or near the same markers across different families/generations, and 32 QTLs were detected in both one-way variance analyses and mixed model-based composite interval mapping. G. mustelinum alleles increased UHM and UI and decreased SFC for five, one, and one QTLs, respectively. In addition to the main-effect QTLs, 17 epistatic QTLs were detected which helped to elucidate the genetic basis of cotton fiber length. Significant among-family genotypic effects were detected at 18, 16, and 16 loci for UHM, UI, and SFC, respectively. Six, two, and two loci showed genotype × family interaction for UHM, UI and SFC, respectively, illustrating complexities that might be faced in introgression of exotic germplasm into cultivated cotton. Co-location of many QTLs for UHM, UI, and SFC accounted for correlations among these traits, and selection of these QTLs may improve the three traits simultaneously. The simple sequence repeat (SSR) markers associated with G. mustelinum QTLs will assist breeders in transferring and maintaining valuable traits from this exotic source during cultivar development.

Genomic Selection for Increased Yield in Synthetic‐Derived Wheat

The loss of genetic diversity in bread wheat (Triticum aestivum L.) due to bottlenecks from polyploidy, domestication, and modern plant breeding can be compensated by introgressing exotic germplasm. A successful approach to capture genetic diversity is the production of primary synthetic bread wheats, which are contemporary reconstitutions of the ancestral genomes of wheat from diverse wild relatives. However, this diverse germplasm has many undesirable characters, making direct use in breeding programs difficult. To increase the speed of introgression of exotic germplasm, genomic selection approaches could be applied to enable rapid cycles of selection. To test this, selected lines from double haploid and recombinant inbred line populations between six different primary synthetics and the elite cultivar ‘Opata M85’ were evaluated for grain yield and other important agronomic traits. Field trials were conducted at CIMMYT (International Center for Maize and Wheat Improvement) over 2 yr in irrigated, heat, and drought‐stressed environments. Several synthetic‐derived lines outperformed the elite parent Opata M85 in all environments, indicating that the primary synthetics contribute alleles increasing yield. Whole‐genome profiles were generated using genotyping‐by‐sequencing. Five different whole‐genome prediction models that can be applied for genomic selection were evaluated for prediction accuracy using cross validation. Overall, the prediction models had moderate predictive ability, slightly lower than expected based on the heritability of the traits. While a viable approach, rapid cycle genomic selection for introgression of exotic alleles might be restricted with synthetic‐derived wheat due to complex and confounding physiological effects.

Genomic Prediction of Gene Bank Wheat Landraces.

This study examines genomic prediction within 8416 Mexican landrace accessions and 2403 Iranian landrace accessions stored in gene banks. The Mexican and Iranian collections were evaluated in separate field trials, including an optimum environment for several traits, and in two separate environments (drought, D and heat, H) for the highly heritable traits, days to heading (DTH), and days to maturity (DTM). Analyses accounting and not accounting for population structure were performed. Genomic prediction models include genotype × environment interaction (G × E). Two alternative prediction strategies were studied: (1) random cross-validation of the data in 20% training (TRN) and 80% testing (TST) (TRN20-TST80) sets, and (2) two types of core sets, “diversity” and “prediction”, including 10% and 20%, respectively, of the total collections. Accounting for population structure decreased prediction accuracy by 15–20% as compared to prediction accuracy obtained when not accounting for population structure. Accounting for population structure gave prediction accuracies for traits evaluated in one environment for TRN20-TST80 that ranged from 0.407 to 0.677 for Mexican landraces, and from 0.166 to 0.662 for Iranian landraces. Prediction accuracy of the 20% diversity core set was similar to accuracies obtained for TRN20-TST80, ranging from 0.412 to 0.654 for Mexican landraces, and from 0.182 to 0.647 for Iranian landraces. The predictive core set gave similar prediction accuracy as the diversity core set for Mexican collections, but slightly lower for Iranian collections. Prediction accuracy when incorporating G × E for DTH and DTM for Mexican landraces for TRN20-TST80 was around 0.60, which is greater than without the G × E term. For Iranian landraces, accuracies were 0.55 for the G × E model with TRN20-TST80. Results show promising prediction accuracies for potential use in germplasm enhancement and rapid introgression of exotic germplasm into elite materials.

Estimation of loss of genetic diversity in modern Japanese cultivars by comparison of diverse genetic resources in Asian pear (Pyrus spp.)

BackgroundPears (Pyrus spp.) are one of the most important fruit crops in temperate regions. Japanese pear breeding has been carried out for over 100 years, working to release new cultivars that have good fruit quality and other desirable traits. Local cultivar ‘Nijisseiki’ and its relatives, which have excellent fruit texture, have been repeatedly used as parents in the breeding program. This strategy has led to inbreeding within recent cultivars and selections. To avoid inbreeding depression, we need to clarify the degree of inbreeding among crossbred cultivars and to introgress genetic resources that are genetically different from modern cultivars and selections. The objective of the present study was to clarify the genetic relatedness between modern Japanese pear cultivars and diverse Asian pear genetic resources.ResultsWe genotyped 207 diverse accessions by using 19 simple sequence repeat (SSR) markers. The heterozygosity and allelic richness of modern cultivars was obviously decreased compared with that of wild individuals, Chinese pear cultivars, and local cultivars. In analyses using Structure software, the 207 accessions were classified into four clusters (K = 4): one consisting primarily of wild individuals, one of Chinese pear cultivars, one of local cultivars from outside the Kanto region, and one containing both local cultivars from the Kanto region and crossbred cultivars. The results of principal coordinate analysis (PCoA) were similar to those from the Structure analysis. Wild individuals and Chinese pears appeared to be distinct from other groups, and crossbred cultivars became closer to ‘Nijisseiki’ as the year of release became more recent.ConclusionsBoth Structure and PCoA results suggest that the modern Japanese pear cultivars are genetically close to local cultivars that originated in the Kanto region, and that the genotypes of the modern cultivars were markedly biased toward ‘Nijisseiki’. Introgression of germplasm from Chinese pear and wild individuals that are genetically different from modern cultivars seems to be key to broadening the genetic diversity of Japanese pear. The information obtained in this study will be useful for pear breeders and other fruit breeders who have observed inbreeding depression.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0380-7) contains supplementary material, which is available to authorized users.

Use of the Suwan1 Heterotic Group in Maize Breeding Programs in Southwestern China

Broadening the maize (Zea mays L.) genetic base is essential for improving grain yield. Suwan1, developed from a broad base of tropical germplasm in Thailand, has recently been identified as a heterotic group different from Reid and non‐Reid heterotic groups. The objectives of this study were (i) to evaluate the grain yield (GY) of crosses to see if there is value to utilizing Suwan1 as a heterotic group in maize breeding, and (ii) to investigate the general combining ability and specific combining ability to determine if Suwan1 shows good combining ability with Reid and non‐Reid heterotic groups for GY. Three testers, one from each of the three heterotic groups, were crossed with 20 elite lines collected from across China. Eighteen lines improved via introgression of exotic germplasm and two lines improved via pedigree selection were crossed with TRL02 (non‐Reid), YML46 (Suwan1), and TRL211 (Reid). Grain yield, ear length, ear diameter, kernel rows per ear, kernels per row, and 100‐kernel weight of crosses and a check were evaluated at three locations. The results suggested that the Suwan1 × temperate crossing system was a very useful heterotic pattern. Suwan1 improved all five yield components in crosses and demonstrated good combining ability for GY with Reid and non‐Reid heterotic groups. We have also determined that the appropriate percentage of introgressed germplasm should be between 6.25 and 12.5%.

Molecular confirmation of Gossypium hirsutum chromosome substitution lines

The primary gene pool for tetraploid cotton species includes Gossypium hirsutum L., as well as the other four 2n = 52 species of Gossypium (G. barbadense, G. mustellinum, G. tomentosum and G. darwinii). To help overcome barriers to effective introgression, we have developed a number of alien chromosome substitution (CS) lines from G. barbadense, G. mustellinum and G. tomentosum, most of which are nearly isogenic to the inbred ‘Texas Marker-1’, a genetic standard. At the time CS line development was initiated, molecular markers did not exist for some CS lines, and most of these lines were developed based on cytological analysis without using any marker-based testing. Here we report on tests with SSR markers from one ore more linkage maps specific to the substituted chromosome or chromosome segment from one or more linkage maps to assess the constitution and genetic identity of the CS lines. The specific objective of this paper is to report on the genetic identity of the CS lines using SSR markers and some special characteristics associated with some of the CS lines. We used chromosome-specific SSR markers following standard methods of DNA extraction, PCR and according to manufacturer’s protocol on ABI Genetic Analyzer 3130xl to confirm the identity of the introgressed alien chromosome or chromosome segments in the CS lines. For most CS lines and most mapped markers, the observed SSR profiles were concordant with expectations as per the results of cytological analysis. For a minority of markers and lines, however, the results were discordant; these markers, linkage groups, and CS lines will be further investigated to understand and define their genetic identity for use as breeding resources. Interspecific germplasm introgression can be useful for genetic improvement of Upland cotton. However, such efforts are constrained by genetic incompatibilities between the species. Our results document for the first time the development of CS lines from G. tomentosum and G. mustelinum. These CS lines will open a new paradigm in cotton breeding program by providing a tool for introgression of useful genes from wild and unadapted species in the genetic improvement of Upland cotton.