Double-cross Hybrids Research Articles

Development of Multi-Parent Advanced Generation Intercross (MAGIC) Mapping Population for QTL Analysis in Rice

A major advantage for researchers in plant and animal genetics lies in the ability to create experimental populations. Such populations mix well characterized founder genomes in controlled pedigrees, and facilitate the investigation of both the genome itself and its relationship with traits and the environment. Traditional experimental populations combine the genomes of two parents with contrasting phenotypes to identify regions of the genome affecting the trait. However, each of these populations captures only a small snapshot of the factors affecting the trait due to the narrow genetic base. It is only possible to detect those genomic regions which differ between the two founders, and all alleles occur with high frequency in the population. Recently, a multi-parent advanced generation intercross (MAGIC) strategy has been proposed to interrogate multiple alleles and to provide increased recombination and mapping resolution. The main objective of developing MAGIC populations is to promote intercrossing and shuffling of the genome, thus increased precision and resolution with which QTLs can be detected due to the increased level of recombination. The Global MAGIC is an attempt to combine traits from several gene pools that have been adapted to different environments. In addition to being a source of potential novel variation, the Global MAGIC population provides useful materials for studying the relative contributions from different crop ecotypes and the level of recombination among exploited genomes constituting this population. An eight Parent-based rice MAGIC population was initiated to develop by employing 2-way, 4-way and 8-way cross along with 8-way intercross hybridization. Nonetheless, the 2-way (Single cross), 4-way (Double cross hybrid) cross has completed during the first year of research program (2018-2019) and subsequently, 8-way cross giving rise to 2 sets (8-wcp set1) having genome ABCDEFGH and 8-wcp set-2 with genome EFGHABCD) of 8-way cross F1 genotypes has accomplished at Aman season of second year (2019-2020) of the project. The eight-way crosses of set 1 (8-wcp set-1) were further intercrossed (Boro 2019) with the reciprocal eight-way crosses set 2 (8-wcp set -2) for establishing altogether 85 eight-way intercross combinations (ABCDEFGH/EFGHABCD) and then, we render this 1-85 group as BUMpop (Bangabandhu University Mapping Population). Progeny from each of the eighty-five 8-way intercrosses were grown, keeping ~ 4 offspring per cross constituting the population size as 85 × 4 = 340 lines. The seeds of BUMpop were progressed to the F6 generation via single seed descent (SSD) method in the field.

تقييم اداء هجن زوجية من الذرة الصفراء تحت مواعيد زراعة تلائم العروة الخريفية في المنطقة الوسطى (مكونات الحاصل )

In order to evaluate the performance of double-cross maize hybrids in planting dates suitable for fall growing season in the middle region of Iraq, a field experiment was conducted at the fields of the College of Agricultural Engineering Sciences - University of Baghdad - Jadriya for the fall season of 2022 using double-cross maize hybrids selected from fifteen double cross hybrid maize resulted from crossing ten single hybrids resulting from crossing five inbred lines using the half-diallel method. These included Hybrid 1 = (1×4)(3×5) from the crossing of (ZM49W3E x CDCNS) (ZM43WIZE x ZM19), Hybrid 2 = (1×2)(3×5) from the crossing of (ZM49W3E × CDCN5) (ZM43WIZE x ZM60), Hybrid 3 = (1×5)(2×4) from the crossing of (ZM60 × ZM19) (ZM43WIZE ×CDN5), Hybrid 4 = (1×2)(4×5) from the crossing of (ZM19 × CDCN5) (ZM43WIZE ×ZM60), and Hybrid 5 = (1×4)(2×3) from the crossing of (ZM60 × ZM49W3E) (ZM43WIZE × ZM19), and their comparison with the synthetic variety IPA5018, and testing them under three planting dates: July 1st, July 15th, and August 1st. The experiment used a randomized complete block design with four replications arranged in a split-plot design. The main plots included the three planting dates, while the subplots included the five double-cross maize hybrids and the control variety. Yield and yield components were studied. The results of the experiment showed high significant effects for the third planting date for all traits except for the number of ears per plant, where the third planting date was superior in the number of grains per ears 660.4, weight of 100 grains 37.83 g , days to physiological maturity 99.67 days, crop growth rate 5.644 g plant-1 day-1, and yield per unit area 14.95 ton ha-1. The superiority of the hybrid (1×2)(3×5) in the number of grains ear-1 and the weight of 100 grains was 542.3 and 36.37, respectively., and this was reflected on the yield per unit area, which reached 11.69 ton ha-1, while hybrid (1×2) (3×5) outperformed in number of ears per plant 1.400 and the same hybrid was the earliest to reach physiological maturity at 97.50 days. The response of the double-cross maize hybrids varied with different planting dates and gave significant interaction for all studied traits except for the number of ears per plant.

Heterosis from eucalypt single and multi-cross hybrids

Hybridizing is one of the most important ways to genetically improve eucalypts; especially to tropical species. Because of the high efficiency of asexual using hybrid heterosis, the current planting eucalypt varieties in most tropical areas in the world are hybrids. It’s well known that crossing different eucalypt species in different ways can create hybrids with different characters. But, it’s unclear what kind of species matings tend to create more heterosis. Here we systematically made and tested hybrids of: pure species by pure species (single cross), pure species by hybrids (three-way cross), hybrids by hybrids (double cross). The tropical eucalypt species we used as parents include: Eucalyptus urophylla, E. grandis, E. pellita, E. tereticornis and hybrids between them. The field testing results found: the overall performance of tree volume was: single cross > three way cross > intraspecies cross > double cross. Their 4-year advantages over intraspecies cross were: 29.9%, 8.0% and -12.5%. The coefficient of variation of the 4 types were: 55.3%, 61.2%, 64.0% and 67.1%. As for the survival rate, 4-year result was: double cross (72.6%) > three way cross (71.6%) > single cross (70.8%) > intraspecies cross (54.0%). This shows that the interspecies hybrids had similar environmental adaption, and they were all significantly higher than that of intraspecies cross. The single and multi-cross hybrids had similar coefficient of variation on survival rate. Combining with the results on family and individual tree level heterosis frequency and magnitude, we found that single-cross has more heterosis on volume growth while muti-cross has more heterosis on adaption. Genetic parameter analysis showed that single-cross hybrids have both high additive and high dominant heritability. But the heritability value on different species combinations can be very different. Three way-cross hybrids had the highest additive heritability, but very low dominant heritability. The double-cross hybrids had high dominant heritability, but very low additive heritability.

Effects of general and specific combining ability and interaction between them for double crosses in zucchini squash (Cucurbita pepo L.)

This study used six inbred lines of squash (Cucurbita pepo L.), which were introduced into a half-diallel crossing program to derive 15 single cross hybrids. According to Rawlings and Cockerham's method of deriving 45 double-cross hybrids, single-cross hybrids were introduced into a double-cross. They included them in various trial experiments and estimations of the general and specific combining ability and gene action of the traits studied. The results showed highly significant differences in the mean square deviations for the double-crosses in all the studied traits. Inbred lines 6, 4 and 1 showed the highest general combining ability with the desired direction on fruit diameter and plant yield, respectively. Also, the double cross hybrids of order S1x2, t(23)(..), t(2.)(6.) showed the highest effect of the specific combining ability to combine on plant yield. Therefore, the effects of the specific combining ability are more important than the effects of the general combining ability in most of the studied traits, including the plant yield, referring to the importance of the dominant genet action and the dominant × dominant in the inheritance of these traits. Keywords: Genetic, squash, half-diallel, combining ability, single cross, Doublecross, breeding plant, hybrids.

Genetic diversity and selection signatures in a gene bank panel of maize inbred lines from Southeast Europe compared with two West European panels

Southeast Europe (SEE) is a very important maize-growing region, comparable to the Corn belt region of the United States, with similar dent germplasm (dent by dent hybrids). Historically, this region has undergone several genetic material swaps, following the trends in the US, with one of the most significant swaps related to US aid programs after WWII. The imported accessions used to make double-cross hybrids were also mixed with previously adapted germplasm originating from several more distant OPVs, supporting the transition to single cross-breeding. Many of these materials were deposited at the Maize Gene Bank of the Maize Research Institute Zemun Polje (MRIZP) between the 1960s and 1980s. A part of this Gene Bank (572 inbreds) was genotyped with Affymetrix Axiom Maize Genotyping Array with 616,201 polymorphic variants. Data were merged with two other genotyping datasets with mostly European flint (TUM dataset) and dent (DROPS dataset) germplasm. The final pan-European dataset consisted of 974 inbreds and 460,243 markers. Admixture analysis showed seven ancestral populations representing European flint, B73/B14, Lancaster, B37, Wf9/Oh07, A374, and Iodent pools. Subpanel of inbreds with SEE origin showed a lack of Iodent germplasm, marking its historical context. Several signatures of selection were identified at chromosomes 1, 3, 6, 7, 8, 9, and 10. The regions under selection were mined for protein-coding genes and were used for gene ontology (GO) analysis, showing a highly significant overrepresentation of genes involved in response to stress. Our results suggest the accumulation of favorable allelic diversity, especially in the context of changing climate in the genetic resources of SEE.

Double cross hybrids could substantially supersede single cross hybrids for yield, fruit quality and tolerance to tomato leaf curl virus disease

ABSTRACT Recombination of commercially available hybrids could produce desirable segregants that act as sources of new alleles for tomato breeding. Seven commercial single cross (SC) hybrids of tomato (Solanum lycopersicum L.) were crossed in a half diallel fashion to obtain 21 double cross hybrids (DC) to estimate combining ability, mode of gene action and extent of heterobeltiosis for fruit yield, processing qualities and tomato leaf curl virus (ToLCV) disease severity traits. Predominance of non-additive gene action occurred in the control for all characters except for total soluble solids (TSS) content in fruit that was conditioned by both additive and non-additive gene action. Improvement of most traits in DC hybrids over SC hybrids occurred. Maximum heterotic effect in DC hybrids was for vitamin C content followed by lycopene content, fruit yield per plant, titratable acidity content, number of fruit per plant and percent disease index of ToLCV. Two good combiners, ‘PAN-1286’ and ‘Devi’ among SC hybrids were identified based on general combining ability effects and average performance. Commercial exploitation of DC hybrids, ‘TO-1458 × L-37’ and ‘NS-501 × TO-1458’ following multilocational testing in the tropics and subtropics might be useful. High yielding, ToLCV disease tolerant DC hybrids could be exploited in segregating generations to identify elite multi-parent advanced generation inter-cross (MAGIC) populations.

Genetic Diversity among Single, Double, And Triple Cross Hybrids in Beit Alpha Cucumber (Cucumis sativus)

Genetic variation was investigated in fifteen single, eighteen three-way, and nine double hybrid crosses and their parents along with nine elite commercial cucumber hybrids. Six lines (NS5, NS9, NS17, NS29, NS31, and NS33) were used to develop these cross hybrids. Based on AFLP and SSR analysis, the studied cucumber genotypes have a narrow genetic base. The results also showed genetic differentiation compared to commercial varieties. Out of 1352 bands produced from 12 AFLP primer pairs, only 47 were polymorphic. Similarly, out of 26 SSR primers, only one primer was polymorphic. The highest heterozygosity index (0.6044), polymorphic information content value (0.5392), and marker Index (0.6044) were observed with M-CTT_E-AAG AFLP primer combination, while the highest effective multiplex ratio (2.8246) and resolving power (4.8421) were observed with M-CTC_E-AGC AFLP primer combination. Genetic distance estimation revealed clear distinctiveness of the studied genotypes with the control varieties. The cluster analysis by UPGMA showed two main clusters covering 84% of the studied genotypes grouped. This research shows that double and three-way hybrid crosses can be used in cucumber hybrid breeding.

Germination characteristics of different maize inbred hybrids and their parental lines

The germination characteristics response for some selected maize hybrids and their parental inbred lines were observed and evaluated in an in vitro trial. The aim of the study was to determine the differences within the performance of some hybridization pathways. Single cross (SC), double cross (DC) and three-way cross (TC) hybrids and their parental inbred lines were studied. The results showed that the germination of maize seeds started after the third day and completely germinated on the seventh day after sowing. Hybrids SC (F1), DC (F1), and TC (F1) showed excellent germination performance with a 100% germination rate on the fifth day and produced the highest shoot and root lengths with 7.9 cm, 7.6 cm, and 6.9 cm (shoot length) and 12.9 cm, 13.9 cm and 14.9 cm (root length), respectively. Thus, the results obtained clearly show that the hybrid seeds have higher germination rate (100%), and the seedlings were more vigorous compared to the parents.

Sample size for canonical correlation analysis in corn

The canonical correlation analysis has been successfully used in many areas aiming to extract important information from a pair of data sets. Thus, the objective of this work was to determine the sample size (number of plants) required to estimate the canonical correlations in corn characteristics. Six characteristics were measured in 361, 373, and 416 plants, respectively, of the single, three-way and double cross hybrids of the 2008/2009 crop year and in 1,777, 1,693, and 1,720 plants, respectively, of the single, three-way, and double cross hybrids (2009/2010 crop) (six cases). The canonical correlation analyses were carried out between characteristics group of the plant architecture (plant height at harvest and ear insertion height) versus grain production (hundred grains mass and grains mass per plant) (scenario 1), and dimensions of ear (ear length and ear diameter) versus grain production (hundred grains mass and grains mass per plant) (scenario 2). The sample size (number of plants) for the estimation of canonical correlations was determined by resampling with replacement and application of the model linear response with plateau. Measuring 270 plants is sufficient to estimate the canonical correlation between groups with two characteristics in each group for corn. This sample size can be used as reference for reliable canonical correlation analysis.

Double Cross Hybrids Performance for Quality and Earliness Traits in some Egyptian Cotton Genotypes

Double Cross Hybrids Performance for Quality and Earliness Traits in some Egyptian Cotton Genotypes

Reproductive resilience but not root architecture underpins yield improvement under drought in maize.

Because plants capture water and nutrients through roots, it was proposed that changes in root systems architecture (RSA) might underpin the 3-fold increase in maize (Zea mays L.) grain yield over the last century. Here we show that both RSA and yield have changed with decades of maize breeding, but not the crop water uptake. Results from X-ray phenotyping in controlled environments showed that single cross (SX) hybrids have smaller root systems than double cross (DX) hybrids for root diameters between 2465 µm and 181µm (P<0.05). Soil water extraction measured under field conditions ranged between 2.6 mm d–1 and 2.9 mm d–1 but were not significantly different between SX and DX hybrids. Yield and yield components were higher for SX than DX hybrids across densities and irrigation (P<0.001). Taken together, the results suggest that changes in RSA were not the cause of increased water uptake but an adaptation to high-density stands used in modern agriculture. This adaptation may have contributed to shift in resource allocation to the ear and indirectly improved reproductive resilience. Advances in root physiology and phenotyping can create opportunities to maintain long-term genetic gain in maize, but a shift from ideotype to crop and production system thinking will be required.

Performance of the double-cross tomato hybrids from a partial diallel

ABSTRACT Knowledge of the combining ability of genotypes, genetic diversity, and heterosis play the paramount role in obtaining double-cross hybrids with high productivity. This study was aimed at evaluating these parameters in tomato genotypes using partial diallel crosses among the commercial single-cross hybrids, which verified the possibility of using double-cross hybrids for commercial purposes. Tomato genotypes included 15 double-cross hybrids, their genitors, and two commercial genotypes as checks. Of the fifteen double-cross hybrids of tomato, two crosses exhibited superiority, such as Aguamiel × Compack and Dominador × Compack, mainly for the total and commercial fruit yields. The phenotypic expression of the trait is controlled by the genes with non-additive effects, whereas the genes with additive effects account for the genotypes of fruit mass, horizontal diameter, vertical diameter, and bunch insertion height. Regarding the genetic diversity, molecular analyses pointed out polymorphism for 79 percent of the evaluated loci evidencing a high genetic variability among the genitors. The heterosis values were low for most of the crosses, except for Forty × Plutão that represented 107 percent of heterosis for the total fruit yield. As compared with the commercial checks, the diallel cross generated superior quality hybrids, which inferred the possibility of obtaining double-cross hybrids of tomato with significant heterosis.

Sample size for principal component analysis in corn

Abstract The objective of this work was to determine the number of plants required to estimate the eigenvalues of the principal components analysis in corn (Zea mays) traits. Twelve traits were measured in 361, 373, and 416 plants of single-, three-way, and double-cross hybrids, respectively, in the 2008/2009 crop year; and in 1,777, 1,693, and 1,720 plants of single-, three-way, and double-cross hybrids, respectively, in the 2009/2010 crop year (six cases), totaling 6,340 plants. Principal component analysis was performed for the six cases. Sample size (number of plants) for the eigenvalue estimations of the principal components was determined by resampling with replacement and application of the model linear response and plateau model. The measurement of 267 plants is sufficient to estimate the eigenvalues of the principal components in corn traits.

SEGREGATION OF THE RR BIOTECHNOLOGY AND AGRONOMICAL VARIABLES IN SINGLE-CROSS, DOUBLE-CROSS, AND F2 HYBRIDS OF MAIZE (ZEA MAYS L.)

The present work evaluated the segregation of the RR-biotechnology and the agronomic performance of maize hybrids originated from three seed categories: single-cross commercial hybrids, double-cross hybrids, and saved seeds (F2 population). The experiment was set up in the field, within a producing area used for market purposes, in São Miguel do Iguaçu, Paraná, Brazil. The research followed a randomized block design with four repetitions. We investigated the following treatments: saved seeds/F2 population (MG 580 PW, MG 30A37 PW, MG 600 PW, and MG 545 PW), seeds of single-cross commercial hybrids (MG 580 PW, MG 30A37 PW, AS 1777 PRO3, AG 9000 PRO3, and DKB 290 PRO3) and home-bred seeds/double-cross hybrids (DKB 290 PRO3 x MG 30A37 PW, DKB 290 PRO3 x DKB 285 PEO3, DKB 290 PRO3 x DOW 2B587 PW, and DKB 290 PRO3 x MG 600 PW). The study considered agronomical characters, as well as the segregation of the RR-biotechnology. The hybrids MG 580 PW and DKB 290 PRO3 were the most productive ones, yielding 9,244.31 and 9,151.84 kg ha-1, respectively. The groups formed by double-cross and F2-population hybrids had the highest average values of RR-biotechnology segregation (20.5% and 13%, respectively). The group of commercial hybrids proved to be superior to the others in all variables appraised, and they also did not show segregation of the RR-biotechnology. The principal component analysis made it possible to sort the three categories of seeds. In conclusion, despite the high cost, the commercial seeds stood out showing the best cost-benefit for maize crops.

Reference sample size for multiple regression in corn

Abstract: The objective of this work was to determine the number of plants required to model corn grain yield (Y) as a function of ear length (X1) and ear diameter (X2), using the multiple regression model Y = β0 + β1X1 + β2X2. The Y, X1, and X2 traits were measured in 361, 373, and 416 plants, respectively, of single-, three-way, and double-cross hybrids in the 2008/2009 crop year; and in 1,777, 1,693, and 1,720 plants, respectively, of single-, three-way, and double-cross hybrids in the 2009/2010 crop year, totaling 6,340 plants. Descriptive statistics were calculated, and frequency histograms and scatterplots were created. The sample size (number of plants) for the estimate of the β0, β1, and β2 parameters, of the residual standard error, the coefficient of determination, the variance inflation factor, and the condition number between the explanatory traits of the model (X1 and X2) were determined by resampling with replacement. Measuring 260 plants is sufficient to adjust precise multiple regression models of corn grain yield as a function of ear length and ear diameter. The Y = -229.76 + 0.54X1 + 6.16X2 model is a reference for estimating corn grain yield.

Progressive heterosis in genetically defined tetraploid maize

Progressive heterosis, i.e., the additional hybrid vigor in double-cross tetraploid hybrids not found in their single-cross tetraploid parents, has been documented in a number of species including alfalfa, potato, and maize. In this study, four artificially induced maize tetraploids, directly derived from standard inbred lines, were crossed in pairs to create two single-cross hybrids. These hybrids were then crossed to create double-cross hybrids containing genetic material from all four original lines. Replicated field-based phenotyping of the materials over four years indicated a strong progressive heterosis phenotype in tetraploids but not in their diploid counterparts. In particular, the above ground dry weight phenotype of double-cross tetraploid hybrids was on average 34% and 56% heavier than that of the single-cross tetraploid hybrids and the double-cross diploid counterparts, respectively. Additionally, whole-genome resequencing of the original inbred lines and further analysis of these data did not show the expected spectrum of alleles to explain tetraploid progressive heterosis under the complementation of complete recessive model. These results underscore the reality of the progressive heterosis phenotype, its potential utility for increasing crop biomass production, and the need for exploring alternative hypothesis to explain it at a molecular level.

Integration of Phenotype and Hormone Data during Adventitious Rooting in Carnation (Dianthus caryophyllus L.) Stem Cuttings.

The rooting of stem cuttings is a highly efficient procedure for the vegetative propagation of ornamental plants. In cultivated carnations, an increased auxin level in the stem cutting base produced by active auxin transport from the leaves triggers adventitious root (AR) formation from the cambium. To provide additional insight into the physiological and genetic basis of this complex trait, we studied AR formation in a collection of 159 F1 lines derived from a cross between two hybrid cultivars (2003 R 8 and 2101-02 MFR) showing contrasting rooting performances. In three different experiments, time-series for several stem and root architectural traits were quantified in detail in a subset of these double-cross hybrid lines displaying extreme rooting phenotypes and their parental genotypes. Our results indicate that the water content and area of the AR system directly contributed to the shoot water content and shoot growth. Moreover, morphometric data and rooting quality parameters were found to be associated with some stress-related metabolites such as 1-aminocyclopropane-1-carboxylic acid (ACC), the ethylene precursor, and the conjugated auxin indol-3-acetic acid-aspartic acid (IAA-Asp).

Genetic progress, adaptability and stability of maize cultivars for value of cultivation and use trials

Maize breeding programs conduct multi-environment trials every year to assess the performance of new cultivars in pre-releasing tests. The data are combined across sites and seasons to perform a joint analysis in order to obtain information that will help breeders to select the best cultivars for different environments. Beyond this, it is essential to understand the different factors that can hamper the selection and genetic progress (i.e., genetic variability, selection intensity and genotype-by-environment interactions). In this study, the genetic progress (GP) was estimated and the adaptability and stability of 81 maize genotypes were evaluated in a series of trials for the value of cultivation and use (VCU) between the 2010/11 and 2014/15 growing seasons. The genotypes were composed of open-pollinated varieties, topcross hybrids, intervarietal hybrids, and single, double and three-way cross hybrids and were assessed in 117 environments in the central region of Brazil, from which 22 presented environmental stresses. For grain yield, an annual GP of 331.5 kg ha-1 was observed, thus showing efficiency in the selection of superior cultivars. Additionally, it was observed that some low-cost seed cultivars showed yield potential, adaptability and stability estimates that were compatible with commercial hybrids, thus making them quite attractive for cultivation in environments with or without abiotic stresses.

Bayesian hierarchical modeling of yield in incomplete diallel crosses of the Pacific oyster Crassostrea gigas

Identifying elite inbred parent lines that produce high-performing hybrid Pacific oyster seed requires diallel or factorial test crosses among lines, each acting as both a male and a female parent. Previously, we used the generalized linear model with fixed effects (i.e. GLM) to partition variance in yield, among hybrid families produced by a diallel cross, into causal genetic components—principally, general combining ability (GCA), specific combining ability (SCA), and reciprocal effect (R). However, GLM is extremely sensitive to missing information, which arises from loss of hybrid families for random environmental causes or from variation in the reproductive success of parent lines. To resolve this issue, we apply a Bayesian hierarchical model, which partitions yield variance into the familiar causal genetic components, while providing Bayesian shrinkage estimates incorporating the uncertainty of missing data. Our study suggests that correlation between observed yields and those predicted by the Bayesian model is high (r2 ≥ 0.99), for observed offspring, regardless of diallel completeness. Additionally, in analyses of complete diallel crosses, line-specific GCA rankings from GLM and Bayesian models are consistent for parent lines. Finally, comparing simulated complete and incomplete diallel datasets, we show the accuracy of predicted yield for families that are present and of parent-line ranking by GCA and the reliability of parent-line selection for double-cross hybrids, especially when non-parental lines (i.e. the four hybrid parents used to predict the yield of double-cross hybrids) are present. Our study demonstrates that the Bayesian hierarchical model performs as well as GLM in analyzing complete diallel crosses and can properly deal with incomplete diallel crosses for which GLM does not work. Therefore, the Bayesian hierarchical model is powerful in diallel analysis to select superior parent lines for producing high-yielding, hybrid, Pacific oyster seed.

Agrarian Crossings: Reformers and the Remaking of the US and Mexican Countryside

Agrarian Crossings: Reformers and the Remaking of the US and Mexican Countryside