Reciprocal differences for forage traits in single and three-way crosses of maize

Eleven flint inbreds of maize were crossed with 11 dent inbreds according to a balanced incomplete factorial mating design to produce 66 single crosses (2W) in both reciprocal forms. Additionally, six three-way crosses (3W) were also produced in both reciprocal forms. These hybrids were evaluated for 11 forage yield and quality traits in 1983 and 1984 at three sites in Germany. Highly significant reciprocal differences were observed for nine traits in the 2W. The respective variance component estimates amounted to 2–33% of the variance component due to crosses. On average, flint × dent 2W had lower dry-matter content (DMC) than dent × flint 2W and a 1 % greater dry-matter yield (DMY) of forage. Three-way crosses produced on singles exhibited greater DMC (3%) and DMY (5%) of the ear, metabolizable energy content (MEC) of stover (1%), and DMC and DMY of forage (2%) than their reciprocal forms produced on lines. Based on this study, because of their minor importance, routine testing for reciprocal differences among 2W hybrids is not recommended.     

Genetic Diversity for RFLPs in European Maize Inbreds

Restriction fragment length polymorphisms (RFLPs) have been proposed for predicting the yield potential of different types of cross. Their has been evaluated in 15 flint and 12 dent inbreds from the European maize (Zea mays L.) germplasm as well as in 68 F₁ crosses (21 flint × flint, 14 dent × dent, and 33 flint × dent) produced between them. The materials were evaluated for F₁ performance and midparent heterosis of grain yield, dry matter content (DMC) and plant height in two environments in Germany. Genetic distances (GDs) between parental lines, calculated from RFLP data of 194 clone-enzyme combinations, showed greater means for flint × dent (0.67) than dent × dent (0.62) and flint × flint (0.55) crosses. Cluster analysis based on GDs resulted in a clear separation of flint and dent lines and agreed well with pedigree information. For the complete set of 64 crosses analyzed (excluding 4 crosses between closely related lines) correlations of GD with F₁ performance and heterosis were significant for all traits except F₁ performance of DMC. When separate calculations were performed for individual subjets of crosses, correlations of GD with Fl performance and heterosis were significantly positive (0.48 ≤ r ≤ 0.80) for all traits in the flint × flint crosses, but not significant for the subsets of flint × dent and dent × dent crosses. Our results confirm those of previous investigations in that the predictive value of RFLP data is restricted to crosses between lines from the same heterotic group, and cannot be applied to crosses between lines from genetically divergent heterotic groups.     

Comparison of intra- and inter-pool crosses in faba beans (Vicia faba L.). II. Genetic effects estimated from generation means in Mediterranean and German environments

Genetic diversity between parents is important for hybrid breeding and for maximum usefulness of a cross in pure line breeding. However, wide crosses may suffer from poor adaptation in the target environments and recombination losses owing to disruption of favourable epistatic gene combinations. In this study we investigated the importance of various gene effects for different traits in the parents and generations F¹ to F⁵ derived from 99 intra- and inter-pool crosses among 20 lines of the Minor, Major, and Mediterranean germplasm pools of faba bean in Mediterranean and German environments. Yield performance of parental inbreds and progenies of crosses in different selfing generations was high in the region of adaptation of the respective germplasm pool. Heterosis for yield was greatest in interpool crosses of Minor × Mediterranean germplasm, amounting to 106% in Mediterranean and 72% in German environments. Interpool crosses exhibited significantly greater heterosis compared with intrapool crosses in both mega-environments. Generation means analysis revealed the importance of additive gene effects and dominance × dominance epistasis in Mediterranean and German environments. Dominance effects and additive × additive epistasis for yield were negligible in most crossing groups. Since intrapool crosses of Mediterranean germplasm in Mediterranean environments and crosses of Minor and Major germplasm in the German environments were most promising, we suggest crosses among adapted germplasm for hybrid breeding and for establishing new base material in line breeding in faba bean.     

Upland rice breeding in Brazil: a simultaneous genotypic evaluation of stability, adaptability and grain yield

A durum wheat recombinant inbred line population developed from PDW 233 × Bhalegaon 4 cross was analyzed in five environments to understand the genetic network responsible for test weight (TW), thousand kernel weight (TKW), grain yield (YLD), spike length (SL), spikelets per spike (SPS), kernels per spike (KER) and kernel weight per spike (KWS). Genotype, environment and their interactions were main sources of variance for all the traits. TW and TKW were influenced by 11 main effect QTL and 6 digenic epistatic interactions detected on chromosomes 2A, 2B, 4B and 7A. Grain yield was influenced by three epistatic interactions and five main effect QTL, of which two on chromosome 2A were most consistent. A major QTL for spike length was observed on chromosome 3B. QTL for spike characters were distributed over 9 chromosomes. All the traits showed significant influence of digenic epistasis (QQ) and, to a certain extent, QTL × environment interactions (QQE). Therefore, while breeding for complex traits like kernel characters and grain yield components, these interactions should also be considered important. The consistent QTL on chromosome 2A between the marker interval Xgwm71.2–Xubc835.4 with pleiotropic effect on TW and TKW, may be utilized in early generation selection to improve TW and TKW and thereby the milling potential of the durum wheat.     

Genetic variation in testcrosses of European maize inbreds for resistance to the European corn borer and relations to line per se performance

The European com borer (ECB) Ostrinia nubilalis H. is a major pest in World maize Zea mays L. production. Objectives of this study were to (1) investigate the genotypic variance and covariance in testcrosses of European flint and dent inbreds for ECB resistance and agronomic traits, and (2) estimate the correlation between line per se and testcross performance for ECB resistance traits. A total of 16 flint and 24 dent inbreds and their testcrosses with two testers from the opposite germplasm pool were evaluated in four and three German environments, respectively. Using artificial infestation with ECB larvae, resistance was assessed by damage rating of stalks, tunnel length in dissected stalks, and relative yield of infested plots compared with protected plots. Yield losses due to ECB damage in testcross hybrids amounted to 40%. Significant genotypic variances between flint and dent lines and high heritabilities were found for damage rating of stalks for both line per se and testcross performance. Heritabilities were low or intermediate for tunnel length and relative grain yield. Correlations between line per se and testcross performance were tight for the damage rating of stalks and moderate for tunnel length and relative yield in both flint and dent germplasm. For damage rating of stalks, per se performance of lines tested in a few environments can be used to predict their testcross performance. In contrast, assessment of testcross performance for tunnel length and relative yield requires evaluating testcrosses with several testers in multi-environment trials.     

Silage yield and quality traits in elite maize hybrids and their relationship to elemental concentrations in juvenile plants

European silage maize is cultivated for animal feed and biogas production. We evaluated 210 factorial crosses of elite dent and flint lines in multilocation trials for agronomic and quality traits together with biomass and shoot concentrations of 10 elements in juvenile plants. Significant genotypic variances, mainly due to general combining ability variance of the dent lines, and high heritabilities were observed for dry matter yield (DMY) and quality traits. DMY was not correlated with quality traits, but methane fermentation yield (MFY) and metabolizable energy content (MEC) showed significant correlations with starch and fibre content. Concentrations of elements N,P,S,K were positively correlated with each other but only in few cases correlated with DMY and quality traits. Parent lines with contrasting P concentrations differed in root morphology traits. Results support DMY as primary trait for selection of silage maize hybrids, but MFY is of negligible importance in breeding for biogas contrary to MEC for animal feed. Neither biomass nor elemental composition of juvenile plants were of predictive value for final DMY or quality traits.     

Genetic Analysis of Developmental Traits in Chickpea

Chickpea (Cicer arietinum L.) is an important legume crop in India. The present study was conducted to investigate the inheritance of several developmental traits in three crosses of chickpea, viz., WFWG III’בT20’, ‘T88’בBold Seeded’, and ‘NP34’בP1528-1-1’, each having seven generations. The seven generations were P₁, P₂, F₁, B₁, B₂, F₂, and F₃. The experimental lay-out was randomized complete block design with three replications. Data were acquired on days to flowering (DF), days to maturity (DM), plant height in cm (PH), number of primary branches (PB), and number of secondary branches (SB). Generation mean analysis was used to estimate the genetic components; narrow sense heritability was estimated using variance components; and correlation analysis to estimate correlation coefficients among different traits. Genetic differences were found in all three crosses for all traits studied. Additive, dominance, and epistatic effects were found for many traits'. Duplicate epistasis was observed for all traits except number of PB. Higher order interactions and/or linkage were detected for DM and SB. For many traits the relative magnitudes of the genetic effects differed among crosses, thus the extrapolation to other crosses may be difficult. The inheritance becomes more complex as the fate of the character is decided at a later stage in the life cycle. Positive heterosis was observed for some traits, but the exploitation of this component may not Feasible since stable male sterile lines are not available. Early maturity and high yield ‘may be selected independently because of the absence of any significant correlation between these two traits.     

Involvement of higher order interactions addressing complex polygenetically controlled inheritance of downy mildew [Sclerospora graminicola (Sacc.) Schrot] resistance in pearl millet [Pennisetum glaucum (L.) R.Br.]

Inheritance of downy mildew [Sclerospora graminicola (Sacc.) Schrot]resistance was studied using generation mean analysis in pearl millet [Pennisetum glaucum (L.) R.Br.]. Eleven basic generations, namely, P₁, P₂, F₁, F₂, B₁, B₂, B₁F₂, B₂F₂, L₁, L₂ and L₃ of three crosses involving six diverse lines for downy mildew incidence were evaluated under artificial epiphytotic conditions over two environments. The downy mildew incidence was best fitting for digenic, trigenic and tetragenic ratios when fitted into classical Mendelian ratios demonstrating involvement of two or more genes. Digenic and trigenic interaction models were adequate in the case of crosses I and III respectively, to account for the total variability in generation means. Unlike severity, comparative estimates of gene effects over two environments were mostly consistent in all crosses for prevalence. Most of the epistatic and major gene effects were found significant in all crosses for both the disease traits. Non-allelic interactions particularly at three-gene loci viz., w (additive × additive × additive) and y (additive × dominance × dominance) in cross II and all trigenic interactions in cross III were predominant. Duplicate dominance (cross I) and complementary epistasis (crosses II and III) were observed for both the traits revealing inconsistency of gene effects over crosses. The gd₁ (interaction of additive gene effect with e₁) and gh₁(interaction of dominant gene effect with e₁) were significant in crosses I and II, indicating interaction of additive and dominance gene effects with environments. Thus a breeding method that can mop up the resistant genes to form superior gene constellations interacting in a favorable manner against pathotype I would be more suitable to accelerate the pace of resistance improvement. This revised version was published online in August 2006 with corrections to the Cover Date.     

QTL for yield components and protein content: a multienvironment study of two pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.) populations

Quantitative trait loci for yield, yield components and seed protein content were investigated on the basis of experiments performed with two populations of pea (Pisum sativum L.) lines derived from linked crosses between lines Wt11238, Wt3557 and Wt10245 with contrasting characteristics. The yield-related traits were defined as components giving the grain yield in a multiplicative way. The aim was to clarify the genetic architecture of the relation between seed yield, its components and protein content, with a possible inclusion of the role of epistasis in this explanation. To take full advantage of the availability of the two populations, additive QTL effects and both types of epistasis were analysed: the QTL by genetic background interaction and the first-order QTL–QTL interaction. The two hybrid populations differed with respect to the prevailing gene action, which in the Wt11238 × Wt3557 progeny was mainly additive, while in the Wt10245 × Wt11238 progeny mainly epistatic. Some loci with previously reported, large, repeatable, but contradictory effects on yield and protein content were confirmed. New loci with alleles coming from the protein-rich Wt11238 line, positive for yield components, were identified. It was found that the first order QTL–QTL interaction events were more frequent for the loci showing the QTL by genetic background interaction.     

Genetic studies for seed size and grain yield traits in kabuli chickpea

Seed size, determined by 100-seed weight, is an important yield component and trade value trait in kabuli chickpea. In the present investigation, the small seeded kabuli genotype ICC 16644 was crossed with four genotypes (JGK 2, KAK 2, KRIPA and ICC 17109) and F₁, F₂ and F₃ populations were developed to study the gene action involved in seed size and other yield attributing traits. Scaling test and joint scaling test revealed the presence of epistasis for days to first flower, days to maturity, plant height, number of pods per plant, number of seeds per plant, number of seeds per pod, biological yield per plant, grain yield per plant and 100-seed weight. Additive, additive?×?additive and dominance?×?dominance effects were found to govern days to first flower. Days to maturity and plant height were under the control of both the main as well as interaction effects. Number of seeds per pod was predominantly under the control of additive and additive?×?additive effects. For grain yield per plant, additive and dominance?×?dominance effects were significant in the cross ICC 16644?×?KAK 2, whereas, additive?×?additive effects were important in the cross ICC 16644?×?JGK 2. Additive, dominance and epistatic effects influenced seed size. The study emphasized the existence of duplicate epistasis for most of the traits. To explore both additive and non-additive gene actions for phenological traits and yield traits, selection in later generations would be more effective.     

Genetic structure composed of additive QTL,epistatic QTL pairs and collective unmapped minor QTL conferring oil content and fatty acid components of soybeans

The relative importance of various types of quantitative trait locus (QTL) conferring oil content and its fatty acid components in soybean seeds was assessed through testing a recombinant inbred line (RIL) population (derived from KF1 × NN1138-2) in randomized blocks experiments in 2004–2006. The contents of oil and oleic, linoleic, linolenic, palmitic and stearic acids were determined with automatic Soxhlet extraction system and gas chromatography, respectively. Based on the established genetic linkage map with 834 markers, QTLNetwork2.0 was used to detect QTL under the genetic model composed of additive, additive × additive (epistasis), additive × year and epistasis × year effects. The contributions to the phenotypic variances of additive QTL and epistatic QTL pairs were 15.7% (3 QTL) and 10.8% (2 pairs) for oil content, 10.4% (3 QTL) and 10.3% (3 pairs) for oleic acid, 11.6% (3 QTL) and 8.5% (2 pairs) for linoleic acid, 28.5% (7 QTL) and 7.6% (3 pairs) for linolenic acid, 27.0% (6 QTL) and 16.6% (7 pairs) for palmitic acid and 29.7% (5 QTL) and 4.3% (1 pair) for stearic acid, respectively. Those of additive QTL by year interaction were small and no epistatic QTL pair by year interaction was found. Among the 27 additive QTL and 36 epistatic QTL (18 pairs), three are duplicated between the two QTL types. A large difference was found between the genotypic variance among RILs and the total variance of mapped QTL, which accounted for 52.9–74.8% of the genotypic variation, much larger than those of additive QTL and epistatic QTL pairs. This part of variance was recognized as that due to a collection of unmapped minor QTL, like polygenes in biometrical genetics, and was designated as collective unmapped minor QTL. The results challenge the breeders for how to pyramid different types of QTL. In addition, the present study supports the mapping strategy of a full model scanning followed by verification with other procedures corresponding to the first results.     

Assessing the suitability of stress tolerant early-maturing maize (Zea mays) inbred lines for hybrid development using combining ability effects and DArTseq markers

Identification of hybrids for commercialization is crucial for sustainable maize production in sub-Saharan Africa (SSA). One hundred and ninety test crosses, 10 tester × tester crosses + 10 hybrid checks were evaluated across 11 environments, 2017 to 2019. Inheritance of grain yield under Striga infestation, optimal and across environments was influenced by additive genetic action, but there was greater influence of nonadditive gene action under drought stress conditions. Nine, seven and two inbreds had significant and positive general combining ability (GCA) effects for grain yield under Striga-infested, optimal and drought stress environments, respectively, and would contribute high grain yield to their progenies. Heterotic grouping methods based on specific and GCA, GCA effects of multiple traits and DArTseq markers classified the inbreds into five, three and two heterotic groups, respectively, across research conditions. The DArTseq markers method that classified the inbred lines into two major heterotic groups and was one of the most efficient methods should be adopted for practical purposes in maize breeding programmes in SSA. Hybrids TZEI 7 × TZdEI 352, TZEI 1238 × TZEI 7 and TZEI 1252 × TZEI 7 had outstanding grain yield under contrasting environments and should be tested on-farm for commercialization in SSA.     

Epistasis in an Andean × Mesoamerican cross of common bean

The objective of this investigation was to check if epistasis is present in Andean × Mesoamerican beans crosses using triple test cross (TTC) method. The parents of the segregating population were Carioca–MG (Mesoamerican) and BRS Radiante (Andean). In July 2005, F₂ progenies (backcrossed with the parents and F₁ generation) were evaluated at two locations for three characters: number of pods plant⁻¹, number of grains plant⁻¹ and grain weight plant⁻¹. The presence of epistasis was detected for all yield components. In the partitioning of epistasis in additive x additive (i) and dominant x dominant (j) and dominant × additive (l) it was observed that, for the traits number of pods/plant and number of grains/plant, only epistasis of the type (j) + (l) were significant. For the trait grain mass/plant, all types of epistasis were significant.     

Evaluation of three cycles of full-sib reciprocal recurrent selection in two maize populations from the Northeast of Spain

In Europe a heterotic pattern commonly used in maize breeding is “American Dent × European Flint”. Maize breeding programs generally use only a small portion of the useful genetic variability present in the local open-pollinated varieties which, otherwise, have a poor performance that hampers their use. Two maize composites, EZS33 formed by open-pollinated flint varieties from dry or Mediterranean Spain, and EZS34 from USA dent populations, were developed in Zaragoza (Spain). Both were subjected to three cycles of full-sib reciprocal recurrent selection (RRS) for yield. The objective of our study was to evaluate after three cycles of selection the effect of RRS. The selection significantly increased yield in the population crosses (3.0 % per cycle) and in the crosses of the populations with testers of different origin. The correlated responses for the population crosses in other agronomic traits like flowering and early vigor were in the desired direction, but plant height was reduced. We propose that stover yield or related traits could be included in selection programs as selection criteria to prevent their decline. The adapted population increased the frequency of favorable alleles for yield, but the inbreeding depression counteracted their effect on the mean. RRS had a positive effect on other traits. According to our data, RRS can be useful to develop improved populations from which it would be possible to develop lines with improved both specific and general combining ability with different heterotic groups. We conclude that the heterotic pattern “Mediterranean Spain × US Dent” is potentially very useful for maize breeding for adaptation to Mediterranean conditions and an interesting source of cultivars for low-input agriculture.     

Multiple‐line cross QTL mapping for grain yield and thousand kernel weight in triticale

Grain yield and its component trait thousand kernel weight are important traits in triticale breeding programmes. Here, we used a large mapping population of 647 doubled haploid lines derived from four families to dissect the genetic architecture underlying grain yield and thousand kernel weight by multiple‐line cross QTL mapping. We identified 3 QTL for grain yield and 13 for thousand kernel weight which cross‐validated explained 5.2% and 48.2% of the genotypic variance, respectively. Both traits showed a positive phenotypic correlation, and we found two QTL overlapping between them. Full two‐dimensional epistasis scans revealed epistatic QTL for both traits, suggesting that epistatic interactions contribute to their genetic architecture. Based on QTL identified in our results, we conclude that the potential for marker‐assisted selection is limited for grain yield but more promising for thousand kernel weight.     

Evaluation of early-maturing European maize inbreds for resistance to the European corn borer

The European corn borer (ECB) has become a serious pest for maize cultivation in Central and Western Europe. This study was conducted to evaluate resistance against ECB in a cross section of the European maize germplasm. A total of 115 flint and dent inbreds were evaluated for resistance under protected and artificial infestation conditions at two German sites in 1993. Resistance to ECB was assessed by damage rating before harvest, tunnel length in dissected stalks, and relative yield under infestation compared to protected control plots. Means for damage rating of stalks were significantly higher in flint lines than in dent lines. Artificial infestation reduced grain yield by 31% in flint lines and 20% in dent lines. Significant genotypic variances among lines and high genetic ratios (GR) were found in both flint and dent lines for all agronomic and ECB resistance traits. Exceptions were relative yield of stover in both germplasm groups and tunnel length in flint lines. Phenotypic correlations between agronomic and resistance traits were moderate to low. Damage rating was negatively correlated with days to silking and dry matter yield of stover in both germplasm groups. In vitro digestibility of stover was not associated with ECB resistance. Correlations of relative grain yield with tunnel length below the ear and damage rating were significantly negative, even though their magnitude was low. Our results indicate substantial genetic variation among European inbred lines for resistance to the univoltine ECB. Among all resistance traits measured, damage rating of stalks is best suited for assessment of ECB resistance in breeding programs because of its easy recording and high genetic ratio. This revised version was published online in July 2006 with corrections to the Cover Date.     

Epistasis in the resistance of pepper to phytophthora stem blight (Phytophthora capsici L.) and its significance in the prediction of double cross performances

Summary Epistatic effects are present in the resistance to Phytophthora capsici in peppers (Capsicum annuum). Genetic statistical analysis shows that additive by additive epistasis as well as higher order epistatic effects contribute to the total variation of resistance, significantly. Higher order epistatic effects caused bias in the prediction of the performance of double crosses, the difference between observed and predicted performances being significant.The relative importance of higher order epistasis with respect to additive by additive epistasis seems to be correlated with the aggressiveness of the isolate of Phytophthora capsici.     

玉米三交种郑三3号高产原因分析

用郑三3号的3个亲本自交系,组配成6个正反单交组合和6个以单交为母本的三交组合,进行产量比较和性状调查。结果表明,6个单交组合之间的产量差异不显著,6个三交组合之间的产量差异亦不显著,说明这3个自交系相互间的配合力都很高,这是郑三3号的产量达到了优良单交种产量水平的内在因素。     

Heterotic relationships among European maize inbreds

European flint maize (Zea mays L.)cannot be considered an uniform group of germplasm based on its origin and area of adaptation. However, maize breeders have not taken full advantage of the variability within the European flint germplasm. The objective of this work was to study the heterotic relationships among European maize inbreds from different origins. Nine European flint inbreds were crossed in a diallel that was evaluated in three environments in northwestern Spain. The variability within the European flint germplasm and the agronomic value of some inbreds could be utilized for maize breeding programs as an alternative to the systematic introduction of U.S. dent germplasm that is narrowing the germplasm base of breeding programs even in places where it is poorly adapted. Some European flint inbreds may also be valuable sources of earliness (F7 and EP42), resistance to root lodging (EA1070), and yield (EP42).These results suggest that, within the European flint germplasm, there could be some heterotic patterns, such as ‘north-central Europe × southern Europe’, which could provide an alternative to the heterotic pattern ‘European flint × U.S. dent’. This revised version was published online in August 2006 with corrections to the Cover Date.     

Reaktion verschiederer Mais-Inzuchtlinien und -Hybriden auf steigendes Stickstoffangebot

Response of maize inbred lines and hybrids to increasing rates of nitrogen fertilizer
The response of 8 flint and 8 dent inbred lines and 16 flint × dent single crosses to three rates of nitrogen fertilizer (80, 160, 240 kg/ha) were tested in the years 1983 and 1984 in field trials at one location. The material represents a broad range of maize genotypes not strongly selected for kernel yield.
The mean kernel yield of all hybrids increased from the lowest to the medium N treatment by 7.6 % in 1983 and by 4.9 % in 1984. The highest fertilizer level resulted in an additional yield advantage in the two years of 6.1 % and 4.4 % respectively. An increased nitrogen rate had a positive effect on plant height, leaf area index, grains/cob, 1000 kernel weight, and protein content. Lodging resistance and dry matter content were not significantly influenced by N treatments. A significant interaction between genotype and N treatment was observed for leaf area index, 1000 kernel weight, and protein content, but not for kernel yield. The correlations of kernel yield with other traits investigated were not consistent over years and nitrogen treatments.