Combining Ability Test Research Articles

Combining ability, floral biology, and seed producibility of promising cytoplasmic male-sterile (CMS) lines for hybrid rice development

BackgroundA combining ability analysis is a useful tool of plant breeders in screening and identifying promising parental lines with high potential for developing competitive rice hybrids. Also, one important factor that strongly determines the suitability of commercial utilization of hybrid rice parental lines is their extent of seed producibility.MethodsIn this study, the combining ability, floral biology and seed producibility of cytoplasmic male sterile (CMS) lines were investigated to identify good combiners with good seed production potential. The Line × Tester analysis was used to determine the general combining abilities (GCA) of hybrid rice parental lines, and Specific Combining Abilities (SCA) of the different hybrid combinations. A correlation analysis was also done to determine floral traits that influence the outcrossing rate of the CMS lines. There were 4 CMS lines, 6 restorer lines, 24 hybrid combinations and 1 check variety in a randomized complete block Design (RCBD) with 3 replicates.ResultsResults indicated that CMS lines IR79128B and IR102758B were good combiners and the most promising restorer lines were D2031-7-1-2R, Hanareumbyeo 2, and XTR036-54-10R. Based on specific combining ability test, the most promising combination was entry 10 (IR58025A/D2013-7-1-2R). It has the highest yield of 7496 kg ha−1, a high positive SCA score of 570.54, and highest standard heterosis of 12.9%. Based on floral traits, IR79128B was the most promising with a high positive GCA score of 186.93, panicle exertion rate of 74.8%, and a high outcrossing rate of 51%. There was a significant positive association between outcrossing rate, duration of floral opening, panicle exertion rate, and general combining ability.ConclusionThe floral traits found to be significantly associated with outcrossing rate are useful selection criteria not only for identifying economically usable CMS lines but also for developing new and promising parental lines and hybrids. These CMS lines do not only give heterotic combinations but are also commercially producible, the two most important factors to the success of any hybrid rice breeding program.

English

Efforts to boost maize productivity can be undertaken through systematic management of heterosis. Combining ability test is a critical step towards identifying a heterotic group of new parental lines. Different heterotic grouping methods has been used by different researchers. Among these, SCA and hybrid mean, hybrid index, combined use of amplified fragment length polymorphism (AFLP), SSR markers and heterotic group’s specific and general combining ability (HSGCA) are the major grouping methods. This study aimed to (i) assign maize inbred lines into heterotic groups and (ii) compare efficiency of different grouping methods. An experiment with 21 maize inbred lines crossed to two testers with known heterotic groups was conducted in 2017. The hybrid and parent experiments were tested together and laid out side by side. This study identified good heterotic grouping procedure. The breeding efficiency of HSGCA was higher by 31.6, 11.0 and 9.6% over joint SCA and hybrid mean, SCA and hybrid index methods, respectively. While the hybrid index method was more efficient than joint SCA and hybrid mean and SCA by 20.1 and 1.3% respectively, the SCA grouping method was more efficient than joint SCA and hybrid mean method by 18.5%. The highest (37%) and lowest (28.1%) breeding efficiency value were scored by HSGCA and hybrid index heterotic grouping method, respectively. Based on the result, HSGCA grouping method was more efficient. The variable heterotic grouping of the 21 newly developed QPM lines in this study indicated that different heterotic grouping methods have different efficiency in grouping the germplasms.   Key words: General combing ability, heterotic-group, inter-group, specific combing ability, within-group, Zea mays.

Combining ability and heterosis for root structure and graft-related traits of interspecific Cucurbita rootstocks

Interspecific hybrid Cucurbita rootstocks (Cucurbita maxima × Cucurbita moschata) are the most widely used rootstocks for Cucurbitaceous vegetables in the world. In recent years, scientists have focused on understanding and exploiting root architectures as new opportunities for crop improvement. Selection of parents and hybrids based on combining ability test is an effective approach in interspecific hybrid variety breeding. However, limited information is available on the combining ability tests for the rooting and graft-related traits in these rootstocks. Ondokuz Mayis University and Black Sea Agricultural Research Institute are conducting a program to breed Cucurbita rootstocks in Turkey for fifteen years. In this study, seven C. maxima (BC5F1 generation) lines as female parents and three C. moschata (S6 generation) lines as male parents were used to obtain 21 crosses. The watermelon grafted onto the interspecific hybrids and their parent rootstocks were analyzed in terms of general combining ability (GCA), specific combining ability (SCA), heritability, and heterosis for roots and graft-related traits including root volume (cm3), root length (m), root dry weight (g), hairy root rate (%), average root diameter (mm), shoot dry weight (g), graft success rate (%), and hypocotyl thickness ratio (%) by using line × tester mating design. The quotient of GCA/SCA effects for all root and hypocotyl traits were higher than 1, suggesting the preponderance of additive over non-additive gene action in the expression of these traits, whereas graft success was controlled by additive and non-additive gene effects. It was determined that average root diameter had high heritability (63.85%) and the other traits had intermediate heritability ranging from 40.59 to 58.98%. Combining ability analyses indicated that FTS5, GH12, and GRD17 lines were promising parents with greater general combining ability. Three crosses, GRD17 × FTS5, B12 × FTS5, and BH5 × CHI2 showed superior mid-parent heterosis and significant SCA for most studied characteristics. Present findings will provide significant contributions in understanding of root related characteristics and then achieving desirable improved rootstocks in C. maxima × C. moschata.

Research on Hybrid Crop Breeding Information Management System Based on Combining Ability Analysis

Combining ability analysis can be used to preliminarily identify the advantages and disadvantages of combinations and parents in earlier generations, enabling breeders to reduce the range of material, save breeding time, and improve breeding efficiency. An approach for combining ability analysis through the hybrid crop breeding information management system is presented. The general combining ability prediction effect of parents and the specific combining ability prediction effect of combinations are calculated to analyze hybrid combinations using the hybrid crop breeding information management system. The results provide the basis for parent selection and combination selection. The plant breeding trial management function of the system can provide convenient diallel crossing trial design, field planting plan, and combining ability analysis. In the system, the genealogy of breeding materials is traced with the combining ability test crosses. The selection of high-generation breeding materials can be performed in accordance with the combining ability test results of early generation materials. The system has been successfully applied to a large Chinese seed company. The combining ability test function automates data analysis and eliminates days in the decision-making process. The efficiency of the combining ability test analysis and test report generation has improved to more than double by using the system.

Combining ability test of parental lines for three-line hybrid rice breeding

Combining ability test of parental lines for three-line hybrid rice breeding

Gene Action and Combining Ability Test for Some Agro-morphological Traits in Barley

Gene Action and Combining Ability Test for Some Agro-morphological Traits in Barley

Combining ability analysis for yield and yield components in rice (Oryza sativa L.)

With the aim of increasing interest in exploitation of heterosis in rice, there is an urgent need to make available various CMS lines and good restoration capability lines for combining ability tests. The knowledge of combining ability is useful to assess nicking ability in self-pollinated crops and at the same time elucidate the nature and magnitude of gene actions involved, provides to the breeder about insight of nature and relative magnitude of fixable and non-fixable genetic variances i.e. due to dominance or epistatic components. This study provides useful information for the selection of donor parents for effective breeding programme. Such informations are required to design efficient breeding programmes for rapid dynamic and strategic crop improvement for quantitative along with qualitative nature of traits. Variation with in crosses and parents were significant for all the characters and also magnitude of variance among parents vs crosses were also significantly for all characters except day to 50% flowering. The SCA variances were higher than the corresponding GCA variances for all the traits. The significant and positive gca effects for grain yield per plant were exhibited only by 3 males namely, Swarna, NDRK 5026 and NDRK 5032 which were found to be good general combiners. Among 24 hybrids studied, none of the hybrids exhibited high sca effects for all 10 characters.

Aptitud combinatoria general y correlaciones fenotipicas entre líneas y mestizos de maíz.

The objectives of this research were: (a) to evaluate the strategy of line selection using the general combining ability test (delayed form), and the performance per se of groups of lines with endogamy levels between S4 and S7. (b) to estimate phenotypic correlation between grain yield and other agronomical traits in lines and hybrids, and between lines and their hybrids, for several economically important factors. Two groups of hybrids were formed, one intermediate and one late cycle. The V-385 C3 was used as the common testero The lines were simultaneously multiplied. The lines themselves and the hybrids were planted in Zapo pan and Tlajomulco, Jalisco, Mexico. Use of late testing (S3 or S4 and later), simultaneous evaluation of the lines themselves, and the graphic method developed were important strategies for selecting lines with a high general combining ability and agronomic quality. The study was also use fuI for reducing the number of lines to evaluate, and for selecting in advance the best type of hybrid to produce. Phenotypic correlation for grain yield between lines and test crosses was similar in the two lines (r= 0.21 and r= 0.20 for intermediate and late lines, respectively), and not significant. This confirms that selecting lines using only the grain yield of their test crosses is not a completely reliable procedure, and justifies the strategy of performing both evaluations.

Growth performance of clonal rubber rootstocks and combining ability test with the scion of clone RRIM 600

Past screening of rubber rootstocks in southern Thailand has revealed five clones that showed good plant growth with tentative tolerance to white root disease. The current study tested the combining ability of these clones with the scion of clone RRIM 600, commonly grown in Thailand. The five clonal rootstocks and the clone RRIM 600 were grown in rhizoboxes (10 × 45 × 100 cm) in a completely randomized design, consisting of six treatments each with four replicates, making a total of 24 rhizoboxes. After growing for 6 mth, each seedling (1 cm stem diameter) was bud grafted with the scion RRIM 600. Root growth of the rootstocks was assessed by scanning a glass panel in the side of each rhizobox after 3 mth. It was found that the seedlings of clone#5 exhibited significantly higher root growth with tentative high shoot growth compared with the remaining treatments. The results showed that clone#5 exhibited the highest average root length density at 1.26 cm/cm2 followed by clone#2 (0.90 cm/cm2) with a significant difference from the other clones. The investigation of graft union development showed that callus tissues developed on the graft union within 5 d after bud grafting (DAB). The graft union growth was almost fully developed over the wound areas and callus bridge formation was evident within 10 DAB. The new vascular tissues were connected with old cambium and vascular tissues of the scion and rootstocks within 20 DAB. The photosynthetic rate and stomatal conductance were assessed and showed 100% successful budding of rootstocks of clone RRIM 600 and clone#4, whereas the other clones achieved 75% success.

Molecular characterization of CIMMYT maize inbred lines with genotyping-by-sequencing SNPs.

Key messageMolecular characterization information on genetic diversity, population structure and genetic relationships provided by this research will help maize breeders to better understand how to utilize the current CML collection.CIMMYT maize inbred lines (CMLs) have been widely used all over the world and have contributed greatly to both tropical and temperate maize improvement. Genetic diversity and population structure of the current CML collection and of six temperate inbred lines were assessed and relationships among all lines were determined with genotyping-by-sequencing SNPs. Results indicated that: (1) wider genetic distance and low kinship coefficients among most pairs of lines reflected the uniqueness of most lines in the current CML collection; (2) the population structure and genetic divergence between the Temperate subgroup and Tropical subgroups were clear; three major environmental adaptation groups (Lowland Tropical, Subtropical/Mid-altitude and Highland Tropical subgroups) were clearly present in the current CML collection; (3) the genetic diversity of the three Tropical subgroups was similar and greater than that of the Temperate subgroup; the average genetic distance between the Temperate and Tropical subgroups was greater than among Tropical subgroups; and (4) heterotic patterns in each environmental adaptation group estimated using GBS SNPs were only partially consistent with patterns estimated based on combining ability tests and pedigree information. Combining current heterotic information based on combining ability tests and the genetic relationships inferred from molecular marker analyses may be the best strategy to define heterotic groups for future tropical maize improvement. Information resulting from this research will help breeders to better understand how to utilize all the CMLs to select parental lines, replace testers, assign heterotic groups and create a core set of breeding germplasm.

Molecular characterization of diverse CIMMYT maize inbred lines from eastern and southern Africa using single nucleotide polymorphic markers

BackgroundKnowledge of germplasm diversity and relationships among elite breeding materials is fundamentally important in crop improvement. We genotyped 450 maize inbred lines developed and/or widely used by CIMMYT breeding programs in both Kenya and Zimbabwe using 1065 SNP markers to (i) investigate population structure and patterns of relationship of the germplasm for better exploitation in breeding programs; (ii) assess the usefulness of SNPs for identifying heterotic groups commonly used by CIMMYT breeding programs; and (iii) identify a subset of highly informative SNP markers for routine and low cost genotyping of CIMMYT germplasm in the region using uniplex assays.ResultsGenetic distance for about 94% of the pairs of lines fell between 0.300 and 0.400. Eighty four percent of the pairs of lines also showed relative kinship values ≤ 0.500. Model-based population structure analysis, principal component analysis, neighbor-joining cluster analysis and discriminant analysis revealed the presence of 3 major groups and generally agree with pedigree information. The SNP markers did not show clear separation of heterotic groups A and B that were established based on combining ability tests through diallel and line x tester analyses. Our results demonstrated large differences among the SNP markers in terms of reproducibility, ease of scoring, polymorphism, minor allele frequency and polymorphic information content. About 40% of the SNPs in the multiplexed chip-based GoldenGate assays were found to be uninformative in this study and we recommend 644 of the 1065 for low to medium density genotyping in tropical maize germplasm using uniplex assays.ConclusionsThere were high genetic distance and low kinship coefficients among most pairs of lines, clearly indicating the uniqueness of the majority of the inbred lines in these maize breeding programs. The results from this study will be useful to breeders in selecting best parental combinations for new breeding crosses, mapping population development and marker assisted breeding.

Inheritance of Antioxidant Activity and its Association with Seedcoat Color in Cowpea

The inheritance of antioxidant activity (AOA) and its association with seedcoat color was investigated in cowpea [Vigna unguiculata (L.) Walp.]. Four advanced cowpea lines, ARK95-356 (black seedcoat) and ARK98-348 (red seedcoat), which were high (H) in AOA, and ARK96-918 (cream seedcoat) and LA92-180 (cream seedcoat), which were low (L) in AOA, were selected from the 2002 Regional Southernpea Cooperative Trials. They were crossed in a complete diallel mating design, generating F1, F1′ (1st generation and 1st generation reciprocal cross, respectively), F2, F2′ (2nd generations from F1, F1′), BC1, and BC2 (backcrosses to parents 1 and 2, respectively) populations. Individual seeds were ground and samples were extracted in methanol and analyzed for AOA using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Combining ability tests using Griffing's Method I Model I indicated presence of highly significant general combining ability (GCA), specific combining ability (SCA), and reciprocal (RE) and maternal (MAT) effects, with pigmented lines exhibiting positive GCA and MAT, while nonpigmented lines exhibited negative GCA and MAT. AOA in the F1 was not significantly different from the maternal parent, with seedcoat color also resembling the maternal parent. Segregation for seedcoat color was observed in the F2 and F2′. Additive, dominance, and epistatic effects were significant. The broad sense heritability estimate was 0.87. Minimum number of genes responsible for AOA was estimated at five. Factors governing high AOA appeared to be the same as those responsible for seedcoat color, with apparent pleiotropic effects. In conclusion, breeding for high AOA in cowpea is possible using highly pigmented parental lines.

Combining Ability, Gene Action and Yielding Performance in Maize

Recombinant lines developed from combining Half-sib/S1 evaluation on widely-spaced plants in the direction of high yielding per se, were used in combining ability tests in order to determine gene action under three-way crossing and possible commercial exploitation of such crosses. Combining ability tests consisted of crosses between: a) recombinant lines of common pedigree, b) recombinant lines and freely available inbred lines and c) recombinant lines and commercial F1 maize hybrids (three-way crosses). Heterosis was found to be acceptable, since the best three-way crosses reached the performance of corresponding single-cross hybrids and yielding performance of these three-way crosses was stable across years and experimental fields. Rapid line development from combining Half-sib/S1 evaluation may ensure high and stable crossing performance, based on additive gene action. Stability and uniformity of performance of three-way crosses was due to proper breeding incorporated in single-cross hybrid and to high and stable inbred line performance

Combining Ability of Origanum majorana L. Strains–Agronomical Traits and Essential Oil Content: Results of the Field Experiment Series in 1999

SUMMARY A combining ability test of 4 cms and 8 pollinator marjoram lines was carried out by a field experiment series on 3 locations to explore the feasibility of a marjoram hybrid variety system. Most traits revealed both–negative and positive–general and specific combining effects depending on the parent components and on the traits. Due to good combining ability high performance hybrids occurred in particular for the essential oil content. In further experiments improved hybrid effects can be expected using more different and homogeneous genotypes.

Combining Ability of Origanum majorana L. Hybrids: Sensorial Quality

SUMMARY Combining ability tests of cms and pollinator marjoram lines were carried out to explore the feasibility of a marjoram hybrid variety system. The performance of colour and taste of the hybrids was influenced mainly in the first year by pollinated as well as pollinator compounds of the hybrids. Smell was only influenced by the pollinators. Bitter tasting hybrid combinations were found in the first test and bitterness was clearly determined by the genetic background of the combinations. These bitter tasting hybrid combinations were strictly eliminated from the breeding process and bitterness hardly occurred in the second test. The correlations between the sensorial parameters were medium to high, but only within each experimental year. The medium correlation between colour and smell or taste indicated a possible influence of the colour impression on consecutive sensorial estimations of a test panel. This correlation furthermore indicated the importance of sensorial colour impression on consumer behaviour not only perceived separately but in correlation to consumers' impressions of smell and taste.

Inbreeding and true seed in tetrasomic potato. IV. Synthetic cultivars

A true potato seed (TPS) synthetic cultivar from open pollination may broaden the genetic base in potato. A synthetic cultivar can also reduce the effect of inbreeding and maintain the productivity from generation to generation. Selected tetraploid parental genotypes, based on combining-ability tests, were chosen for isolated polycrosses to obtain tetraploid offspring. A series of experiments were undertaken to investigate the development of these TPS synthetic populations in two Peruvian locations: San Ramon, a rainfed, humid, mid-altitude environment, and La Molina, an arid, coastal environment under irrigation. Natural open-pollinated synthetics or control-mixture synthetics, involving two to six parents, had a similar tuber set but plant survival and tuber weight were higher in control synthetics including two or six parents. The results suggest that two-parent open-pollinated TPS synthetics may be a feasible option by selecting the right parents for the base population. A subsequent experiment showed that four-parent control synthetics (i.e. double crosses) were the best for tuber weight and size, followed by the two-parent control synthetics. Synthetic breeding populations could be shared with other breeders, who in cooperation with their local farmers may select promising genotypes for further cultivar release.

The combining ability of recombinant S-lines developed from an F2 maize population

Starting with the F2 generation of the single-cross commercial hybrid Lorena (PR3183), recombinant lines were developed combining half-sib/S1 evaluation on widely spaced plants in the direction of high yielding per se. Combining ability tests consisted of crosses between: (a) recombinant lines of common pedigree and (b) recombinant lines and freely available inbred lines. The highest-yielding crosses between recombinant lines reached 100% of the original F1 hybrid in a percentage of 14·2. Low heterosis was estimated owing to additive gene action of recombinant lines. Crosses between recombinant lines and freely available inbred lines outyielded significantly the commercial F1 hybrid in a percentage of 33·3. Heterosis was greater and the original F1 hybrid was outyielded significantly because of non-additive gene action. When the applied breeding procedure on a source population with high yield adaptability is adopted and where effects of intergenotypic competition masking the inherent genotypic value are controlled, population improvement may be substituted by combined half-sib/S1 selection for productivity of lines per se in low stress conditions during the very early stages.

DEVELOPMENT OF A NUMBER OF PARTHENOCARPIC CUCUMBER HYBRIDS IN IRAQ

The objective was to develop Fl parthenocarpic cucumber hybrids adapted to greenhouse and plastic house culture. Thirteen gynoecious inbred lines were developed through successive selfing for six generations, followed by strict selection and screening in each cycle. General and specific combining ability tests were conducted using all possible reciprocal crosses. Four Fl hybrids were selected and compared in variety trials in different seasons with the commercially grown `Maram' hybrid. The local hybrid IPA-C2005 ranked the best for various yield components. No significant difference was observed between the yield of IPA-C2005 and `Maram' hybrid. The marketable yield estimates were 2.182 and 2.150 MT/180Mz for both hybrids, respectively.

Inheritance pattern for pod lenghth and ovule number in wide crosses among Cajanus and Atylosia species

Six interspecific/intergeneric F2 populations involving two cultivars of C. cajan and five Atylosia species were scored for segregation patterns for pod length and ovule number. It was observed that for both characters the F2 means and the ranges were correspondingly lower than the midparent values and the spread of the two parents. However, the intrageneric cross of A. lineata and A. scarabaeoides showed transgressive segregation for pod length and the F2 mean and range were correspondingly larger than the midparent value and spread of the two parents, suggesting the usefulness of combining ability test for choice of suitable parents.

MINIMUM NUMBER OF INDIVIDUALS REQUIRED FOR COMBINING ABILITY TESTS IN RECURRENT SELECTION IN PLANT BREEDING

Minimum number of individuals required for combining ability tests in reccurent selection methods and the change rate of that number were estimated by numerical computations derived from theoretical formulae.