scholarly journals Use of F2 bulks in training sets for genomic prediction of combining ability and hybrid performance

2018 ◽  
Author(s):  
Frank Technow
Keyword(s):  
Genomic Prediction ◽  
Combining Ability ◽  
Hybrid Breeding ◽  
F1 Hybrids ◽  
Hybrid Performance ◽  
Crop Species ◽  
Heterotic Groups ◽  
Quantitative Genetic ◽  
Hand Pollination ◽  
Training Sets

ABSTRACTDeveloping training sets for genomic prediction in hybrid crops requires producing hybrid seed for a large number of entries. In autogamous crop species (e.g., wheat, rice, rapeseed, cotton) this requires elaborate hybridization systems to prevent self-pollination and presents a significant impediment to the implementation of hybrid breeding in general and genomic selection in particular. An alternative to F1 hybrids are bulks of F2 seed from selfed F1 plants (F1:2). Seed production for F1:2 bulks requires no hybridization system because the number of F1 plants needed for producing enough F1:2 seed for multi-environment testing can be generated by hand-pollination. This study evaluated the suitability of F1:2 bulks for use in training sets for genomic prediction of F1 level general combining ability and hybrid performance, under different degrees of divergence between heterotic groups and modes of gene action, using quantitative genetic theory and simulation of a genomic prediction experiment. The simulation, backed by theory, showed that F1:2 training sets are expected to have a lower prediction accuracy relative to F1 training sets, particularly when heterotic groups have strongly diverged. The accuracy penalty, however, was only modest and mostly because of a lower heritability, rather than because of a difference in F1 and F1:2 genetic values. It is concluded that resorting to F1:2 bulks is, in theory at least, a promising approach to remove the significant complication of a hybridization system from the breeding process.

scholarly journals Combining ability and heterosis in plant improvement

2021 ◽  
pp. 108-117
Author(s):  
Begna Temesgen
Keyword(s):  
Genetic Diversity ◽  
Combining Ability ◽  
Crop Improvement ◽  
Critical Factor ◽  
Hybrid Vigor ◽  
Hybrid Breeding ◽  
F1 Hybrids ◽  
Gene Pools ◽  
Crop Species ◽  
Heterotic Groups

Information on combining ability and heterosis of parents and crossings is crucial in breeding efforts. Genetic variety is crucial to the effectiveness of yield improvement efforts because it helps to broaden gene pools in any given crop population. The genotype's ability to pass the intended character to the offspring is referred to as combining ability. As a result, information on combining ability is required to determine the crossing pairs in the production of hybrid varieties. Heterosis is the expression of an F1 hybrid's dominance over its parents in a given feature, as measured not by the trait's absolute value, but by its practical use. To put it another way, heterosis is defined as an increase in the character value of F1 hybrids when compared to the average value of both parents. A plant breeder's ultimate goal is to achieve desirable heterosis (hybrid vigor). In a variety of crop species, heterosis has been widely employed to boost output and extend the adaptability of hybrid types. A crucial requirement for discovering crosses with significant levels of exploitable heterosis is knowledge of the quantity of heterosis in different cross combinations. Any crop improvement program's success is contingent on the presence of a significant level of genetic diversity and heritability. The lack of a broad genetic foundation is the most significant constraint to crop improvement and a major bottleneck in breeding operations. Heterosis is a critical factor in hybrid generation, particularly for traits driven by non-additive gene activity. To get the most out of heterosis for hybrid cultivar production, germplasm must be divided into distinct heterotic groups. Similarly, knowledge on genetic diversity is critical for hybrid breeding and population improvement initiatives because it allows them to analyze genetic diversity, characterize germplasm, and categorize it into different heterotic groupings. In general, general combining ability is used to detect a line's average performance in a hybrid combination, whereas specific combining ability is used to find circumstances where definite combinations perform better or worse than expected based on the mean performance of the lines involved.

scholarly journals Hybrid Breeding for MLN Resistance: Heterosis, Combining Ability, and Hybrid Prediction

Plants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 468
Author(s):  
Christine Nyaga ◽  
Manje Gowda ◽  
Yoseph Beyene ◽  
Wilson T. Murithi ◽  
Juan Burgueno ◽  
...  
Keyword(s):  
Disease Severity ◽  
Combining Ability ◽  
Genetic Parameters ◽  
Artificial Inoculation ◽  
Hybrid Breeding ◽  
Hybrid Performance ◽  
Hybrid Prediction ◽  
Quantitative Genetic ◽  
Per Se ◽  
Quantitative Genetic Parameters

Prior knowledge on heterosis and quantitative genetic parameters on maize lethal necrosis (MLN) can help the breeders to develop numerous resistant or tolerant hybrids with optimum resources. Our objectives were to (1) estimate the quantitative genetic parameters for MLN disease severity, (2) investigate the efficiency of the prediction of hybrid performance based on parental per se and general combining ability (GCA) effects, and (3) examine the potential of hybrid prediction for MLN resistance or tolerance based on markers. Fifty elite maize inbred lines were selected based on their response to MLN under artificial inoculation. Crosses were made in a half diallel mating design to produce 307 F1 hybrids. All hybrids were evaluated in MLN quarantine facility in Naivasha, Kenya for two seasons under artificial inoculation. All 50 inbreds were genotyped with genotyping-by-sequencing (GBS) SNPs. The phenotypic variation was significant for all traits and the heritability was moderate to high. We observed that hybrids were superior to the mean performance of the parents for disease severity (−14.57%) and area under disease progress curve (AUDPC) (14.9%). Correlations were significant and moderate between line per se and GCA; and mean of parental value with hybrid performance for both disease severity and AUDPC value. Very low and negative correlation was observed between parental lines marker based genetic distance and heterosis. Nevertheless, the correlation of GCA effects was very high with hybrid performance which can suggests as a good predictor of MLN resistance. Genomic prediction of hybrid performance for MLN is high for both traits. We therefore conclude that there is potential for prediction of hybrid performance for MLN. Overall, the estimated quantitative genetic parameters suggest that through targeted approach, it is possible to develop outstanding lines and hybrids for MLN resistance.

scholarly journals Reproductive Cold Stress Tolerance in Sorghum F1 Hybrids is a Heterotic Trait

Agronomy ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 508
Author(s):  
André Schaffasz ◽  
Steffen Windpassinger ◽  
Rod Snowdon ◽  
Benjamin Wittkop
Keyword(s):  
Cold Stress ◽  
Cold Tolerance ◽  
Combining Ability ◽  
Pollen Viability ◽  
Field Trials ◽  
Hybrid Breeding ◽  
F1 Hybrids ◽  
F1 Hybrid ◽  
Poor Seed ◽  
High Heritability

The sensitivity of sorghum to pre-flowering cold stress, resulting in reduced pollen viability and poor seed set, is a major constraint for expanding growing areas into higher altitudes and latitudes. Nevertheless, compared to juvenile cold tolerance, reproductive cold tolerance in sorghum has received much less attention so far, and very little is known about its inheritance in F1-hybrids. We have composed a representative factorial (n = 49 experimental F1-hybrids) for a comprehensive study on heterosis and combining ability for crucial tolerance traits as spikelet fertility (panicle harvest index), seed yield and pollen viability, using field trials in stress- and control environments in Germany and Mexico as well as climate chamber experiments. Our results indicate a heterotic and rather dominant inheritance of reproductive cold tolerance in sorghum, with strong effects of female general combining ability (GCA) on F1-hybrid performance in our material. These findings, together with the comparatively low contribution of specific combining ability (SCA) effects and high heritability estimates, suggest that robust and efficient enhancement of reproductive cold tolerance is feasible via hybrid breeding.

scholarly journals Applications of molecular markers in Genetic Diversity Studies of maize

2020 ◽  
Vol 37 (1) ◽  
pp. 101-108
Author(s):  
Degife Asefa Zebire
Keyword(s):  
Genetic Diversity ◽  
Molecular Markers ◽  
Inbred Lines ◽  
Hybrid Breeding ◽  
Diversity Analysis ◽  
Crop Species ◽  
Heterotic Groups ◽  
Genetic Diversity Analysis ◽  
Diversity Studies ◽  
Genetic Diversity Study

Molecular markers are efficient for exploiting variations in genotypes as they are not influenced by environmental factors and also speed up breeding programs. They are used to detect large numbers of distinct divergence between genotypes at the DNA level. Genetic diversity study helps to estimate the relationship between inbred lines to make the best hybrid combinations. Lines which are clustered in different heterotic groups are considered as the best hybrid combinations to carry out further breeding activities. Molecular markers are used to meet a number of objectives, including genetic diversity analysis and prediction of hybrid performances in divergent crop species. Agro-morphological and molecular markers have been utilized to study genetic diversity so far. In maize, the uses of molecular markers are important for the evaluation of genetic diversity of inbred lines and in clustering them into heterotic groups. These markers determine genetic similarity of the lines and are used to assess the genetic diversity of maize. Molecular markers have proven valuable for genetic diversity analysis of many crop species and genetically diverse lines are important to improve hybrid breeding. Keyword: Molecular marker; Genetic diversity; Genetic variation, Diversity Array technology; cluster analysis

scholarly journals Efficiencies of Heterotic Grouping Methods for Classifying Early Maturing Maize Inbred Lines

Agronomy ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1198
Author(s):  
Oyeboade Adebiyi Oyetunde ◽  
Baffour Badu-Apraku ◽  
Omolayo Johnson Ariyo ◽  
Christopher Olusanya Alake
Keyword(s):  
Grain Yield ◽  
Genetic Distance ◽  
Combining Ability ◽  
Diallel Cross ◽  
Hybrid Breeding ◽  
Multiple Traits ◽  
Heterotic Groups ◽  
Maize Hybrids ◽  
Heterotic Grouping ◽  
Additive Gene

The success of a hybrid breeding program is dependent on available heterotic patterns for exploitation of grain-yield heterosis. The efficiency of the assignment of germplasm lines into heterotic groups is a prerequisite for obtaining useful heterotic patterns among germplasm lines. A total of 256 maize hybrids, comprising 244 top crosses, six diallel cross hybrids, and six checks, were grown under Striga infestation, drought, and optimal conditions, from 2015 to 2017. The study determined the combining abilities of the parental inbreds, classified the inbreds into heterotic groups, and compared the efficiencies of the following four grouping methods for classifying the inbreds: specific combining ability (SCA) effect of grain yield; general combining ability (GCA) effects of multiple traits (HGCAMT); SCA and GCA (HSGCA) for yield; and single nucleotide polymorphism-based genetic distance (SNP-based genetic distance (GD)). Significant GCA and/or SCA mean squares were revealed for most measured traits in all test environments. Sums of squares (SS) due to GCA were higher than SCA SS for measured traits in all test environments. The HSGCA, SCA, and SNP-based GD methods identified four heterotic groups, whereas the HGCAMT identified three groups, in all environments. The additive gene effect was preponderant in the inheritance of most measured traits. The efficiencies of the grouping methods varied with the test environments. The HSGCA and SCA methods were the most efficient for grouping in all test conditions. For practical breeding purposes, the HGCAMT and HSGCA methods were recommended under Striga infestation and drought, respectively. The heterotic patterns, which were revealed in this study, were effective for planning hybridization schemes for developing high-yielding, Striga-tolerant/resistant, and drought-tolerant maize hybrids for stressful environments.

scholarly journals PREDICTION OF COMBINING ABILITY AND HETEROSIS IN THE SELECTED PARENTS AND HYBRIDS IN RICE (Oryza Sativa.L)

2017 ◽  
Vol 26 (1) ◽  
pp. 31
Author(s):  
Yuni Widyastuti
Keyword(s):  
Grain Yield ◽  
Combining Ability ◽  
Block Design ◽  
Hybrid Breeding ◽  
F1 Hybrids ◽  
Field Station ◽  
Yield Trait ◽  
Good Potential ◽  
Parental Lines ◽  
Selection Of

<p>Selection of parents based on their combining ability is an effective approach in hybrid breeding. Four CMS and four restorer lines were crossed in line x tester mating design to obtain 16 F1 hybrids rice. The 8 parental lines and 16 hybrids rice were planted in randomized complete block design with three replications at Kuningan and Muara field station of ICRR during 2012-2013. The results revealed that mean squares for GCA were significant for number of fertile spikelet per panicle, a thousand-grains weight, and 50% days of flowering. Mean squares for SCA were significant for plant height and grain yield. Parental lines exhibited the highest GCA effects for GMJ12A (line) and CRS703 (tester) for grain yield trait and revealed good potential to be used as parents for hybrid rice. Among all the crosses, GMJ6A/CRS707 and GMJ12A/CRS707 showed the greatest positive SCA effects for grain yield and had heterosis over better parent and midparent.</p>

Genetic variation in sorghum as revealed by phenotypic and SSR markers: implications for combining ability and heterosis for grain yield

2016 ◽  
Vol 15 (4) ◽  
pp. 335-347 ◽  
Author(s):  
Beyene Amelework ◽  
Hussien Shimelis ◽  
Mark Laing
Keyword(s):  
Genetic Variation ◽  
Grain Yield ◽  
Ssr Markers ◽  
Combining Ability ◽  
Moisture Stress ◽  
Hybrid Breeding ◽  
Male Sterile ◽  
Heterotic Groups ◽  
Lattice Design ◽  
Sorghum Genotypes

AbstractHybrid breeding relies on selection of genetically unrelated and complementary parents for key traits. The objective of this study was to examine genetic variation and identify unique sorghum genotypes using phenotypic and simple sequence repeat (SSR) markers and to determine their relationships with combining ability and heterosis for grain yield. A total of 32 landraces and four cytoplasmic male sterile (CMS) lines were phenotyped using 25 agro-morphological traits and genotyped with 30 polymorphic SSR markers. The landraces were crossed with four CMS lines using a line × tester mating design. The 128 hybrids, 36 parentals and four check varieties were field-evaluated using a 12 × 14 alpha lattice design with three replications. General combining ability (GCA), specific combining ability (SCA) and heterosis for grain yield were determined. Genetic distance estimates ranged from 0.39 to 0.60 and 0.50 to 0.79, based on phenotypic and SSR markers, respectively. Landraces 72572, 75454, 200654, 239175, 239208, 244735A and 242039B and CMS lines ICSA 743 and ICSA 756 displayed positive and significant GCA effects for grain yield. Based on the SCA effects of yield, lines were classified into three heterotic groups aligned to the different cytoplasmic systems of testers. Lines with high GCA effects rendered hybrids with highly significant SCA effects with high mid-parent heterosis (MPH) for grain yield. Both marker systems were effective in demarcating sorghum genotypes that provided desirable cross-combinations with high combining ability effects and MPH for grain yield. The selected genotypes are recommended as potential parents for sorghum hybrid breeding in moisture stress environments.

scholarly journals Genomic prediction of hybrid crops allows disentangling dominance and epistasis

Genetics ◽  
2021 ◽  
Author(s):  
David González-Diéguez ◽  
Andrés Legarra ◽  
Alain Charcosset ◽  
Laurence Moreau ◽  
Christina Lehermeier ◽  
...  
Keyword(s):  
Genomic Prediction ◽  
Combining Ability ◽  
Additive Genetic Variance ◽  
Higher Order ◽  
Heterotic Group ◽  
Substitution Effects ◽  
Genomic Context ◽  
Data Set ◽  
Heterotic Groups ◽  
Pure Lines

AbstractWe revisited, in a genomic context, the theory of hybrid genetic evaluation models of hybrid crosses of pure lines, as the current practice is largely based on infinitesimal model assumptions. Expressions for covariances between hybrids due to additive substitution effects and dominance and epistatic deviations were analytically derived. Using dense markers in a GBLUP analysis, it is possible to split specific combining ability into dominance and across-groups epistatic deviations, and to split general combining ability (GCA) into within-line additive effects and within-line additive by additive (and higher order) epistatic deviations. We analyzed a publicly available maize data set of Dent × Flint hybrids using our new model (called GCA-model) up to additive by additive epistasis. To model higher order interactions within GCAs, we also fitted “residual genetic” line effects. Our new GCA-model was compared with another genomic model which assumes a uniquely defined effect of genes across origins. Most variation in hybrids is accounted by GCA. Variances due to dominance and epistasis have similar magnitudes. Models based on defining effects either differently or identically across heterotic groups resulted in similar predictive abilities for hybrids. The currently used model inflates the estimated additive genetic variance. This is not important for hybrid predictions but has consequences for the breeding scheme—e.g. overestimation of the genetic gain within heterotic group. Therefore, we recommend using GCA-model, which is appropriate for genomic prediction and variance component estimation in hybrid crops using genomic data, and whose results can be practically interpreted and used for breeding purposes.

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