Analysis of combining ability and gene action studies for grain yield and its component traits in bread wheat utilizing line x tester mating design

The present research investigation was conducted in order to analyze combining ability and nature of gene actions in 33 F1s of bread wheat (Triticum aestivum L. em. Thell) developed by crossing eleven lines with three testers in a line x tester mating design in terms of grain yield and associated traits. The hybrids along with the parental lines and two check varieties were planted in a randomized block design in three replications. Variance ratio between general and specific combining ability was found to be less than unity which indicated the prevalence of non-additive gene actions involved in the inheritance of these characters. Parental lines QLD 75 (3.164), followed by SOKOLL (2.888) and QLD 65 (2.819) exhibited significant GCA for grain yield, while another line PRL/2*PASTOR*2//FH6-1-7/3/KINGBIRD#1//… was observed to be the better general combiner for most other traits including maturity. Among the hybrids cross combination NAC/TH.AC//3*PVN/3/MIRLO/BUC/4/2*PASTOR/5/…x HD 3237 showed significant higher positive SCA for grain yield and biological yield per plant, whereas, F1 QLD 75 x HI 1621was a good specific combiner for harvest index (%) and number of grains per spike. The cross combination VORB/4/D67.2/PARANA66.270 x PBW 725 was observed with significant higher positive SCA for days to 75% heading, days to maturity and plant height, and another hybrid VORB/4/D67.2/PARANA 66.270 x HI 1621 exhibited significant positive SCA for 1000 grain weight and spike length.

Combining Ability and Gene Action for Yield Improvement in Kenaf (Hibiscus Cannabinus L.) Under Tropical Conditions Through Diallel Mating Design

Nine morphologically distinct kenaf genotypes were hybridized to produce 36 hybrids following a half diallel mating design. The combining ability and gene action of 15 yield and yield components were assessed in hybrids and their parents across two environments. Except for the mid diameter and plant height traits, there were highly significant differences (p ≤ 0.01) between both the analysis of variance of environments and the interaction of genotype and environment. For the inheritance of these traits, additive gene effects were considerable, and the expression of these additive genes was heavily influenced by the environment. Significant differences were found for all studied traits for GCA except top diameter, and SCA except plant height and top diameter, implying the presence of both additive and non-additive gene action for the inheritance of the concerned characters. For all features except top diameter and number of nodes, the magnitude of GCA variation was significantly higher than that of SCA variance, indicating the additive gene's predominance. The parental lines P1, P3 and P4 were determined to be outstanding general combiners for fibre yield and yield-related parameters. Considering combining ability and genetic analysis study together, the crosses P1 × P4, P1 × P9, P2 × P3, P2 × P5, P4 × P6, P4 × P7, P4 × P9, P5 × P8, and P7 × P9 were found promising for their heterotic response to higher fibre yield, stick yield, seed yield and and could be useful by adopting proper strategies for future improvement in kenaf breeding programmes.

Study of Combining Ability and Heterosis in Quality Protein Maize using Line x Tester Mating Design

Background: High protein content with good quality maize is likely to gain wider acceptance if hybrids are produced that have agronomic performance similar to normal hybrids and retain an enhanced nutritional quality. Thus, an attempt was made to develop quality protein maize hybrids for the benefit of different sections of society depending on maize. Methods: During the Rabi season of 2016-17 (hybrids were obtained crossing ten inbred lines and four testers following Line x Tester mating design) and 2017-18 (evaluation of hybrids and parents involved along with two commercial checks based on different agro-morphological traits). Result: Highly significant differences were observed among lines, testers and crosses. Combining ability revealed SCA variances was higher indicating preponderance of non-additive gene action. The contribution of line x tester interaction was higher suggesting parents used in this study can provide high heterotic cross combinations. The parents CML 508, CML 163-D and CML 169 were superior general combiners, indicating their efficacy as parents in future maize breeding programs. Heterosis identified superior yield advantage of the crosses namely, CML508 x CML154-2, CML170 x CML169 and CML163-D x DMRQPM103 over the standard commercial checks HQPM1 and 900 M Gold.

Assessment of combining ability in purple corn parents under line × tester mating design using GGE biplot

Mufidah N, Sugiharto AN, Waluyo B. 2021. Assessment of combining ability in purple corn parents under line × tester mating design using GGE biplot. Biodiversitas 22: 4545-4554. One strategy to increase corn quality is the development of new corn cultivars by incorporating the character of nutritional content. The study aims to obtain information on the combining ability of purple corn lines as well as determine the best parental lines for purple corn hybrid development using the GGE biplot approach. This study used 24 hybrids generated from crossings of 8 purple corn lines with 3 testers, which were crossed using a line × tester mating design. Plant performance was assessed using a randomized block design of three replications. The F-test was used to assess and test the experiment variance. The combining ability of purple corn lines was examined using the GGE biplot method. The result showed that the GGE biplot approach successfully identified the best combiner and combinations generated between purple corn lines and non-purple corn lines. Purple corn lines P1Y1 had the best general combining ability for fresh ear yield and total anthocyanin content, meanwhile, P1Y2 had the best general combining ability in most of the agronomic traits, namely ear diameter, shelled ear weight, number of grains row-1, and as well as total anthocyanin content. These 2 lines were also identified as the best parent chosen in the best combination in this study.

Estimation of Heterosis in Okra [Abelmoschus Esculentus (L.) Moench] for Fruit Yield and Its Components Through Line × Tester Mating Design

Estimation the magnitude of heterosis for yield and yield contributing parameters of Okra was conducted. Fifty-four F1 hybrids were generated by line x tester mating design. These F1s along with 21 parents and commercial check (Mhyco-10) were evaluated in a randomized block design with two replications. Analysis of variance with respect to yield and quality characters in parents and hybrids were highly significant. This indicates the existence of high variation in parents and hybrids for different characters studied. Out of 54 cross combinations, seven crosses revealed the significant and positive heterosis over better parent. While 11 crosses showed positive and significant heterosis over economic parent. It is pertinent to mention that the crop has potential to produce the heterotic cross combinations and such crosses can be used for further improvement of this crop. Five crosses, namely L43 × T44, L22 × T36, L22 × T44, L53 × T36 and L31 × T23 were found to be potential for the production of fruit yield per plant and other desired characters. The high heterosis and per se performance was found in hybrid L43 × T44 over both better parents and standard check for fruit yield per plant. This indicates that the cross can be exploited commercially. Bangladesh J. Bot. 50(3): 531-540, 2021 (September)

Strategies to Assure Optimal Trade-Offs Among Competing Objectives for the Genetic Improvement of Soybean

Plant breeding is a decision-making discipline based on understanding project objectives. Genetic improvement projects can have two competing objectives: maximize the rate of genetic improvement and minimize the loss of useful genetic variance. For commercial plant breeders, competition in the marketplace forces greater emphasis on maximizing immediate genetic improvements. In contrast, public plant breeders have an opportunity, perhaps an obligation, to place greater emphasis on minimizing the loss of useful genetic variance while realizing genetic improvements. Considerable research indicates that short-term genetic gains from genomic selection are much greater than phenotypic selection, while phenotypic selection provides better long-term genetic gains because it retains useful genetic diversity during the early cycles of selection. With limited resources, must a soybean breeder choose between the two extreme responses provided by genomic selection or phenotypic selection? Or is it possible to develop novel breeding strategies that will provide a desirable compromise between the competing objectives? To address these questions, we decomposed breeding strategies into decisions about selection methods, mating designs, and whether the breeding population should be organized as family islands. For breeding populations organized into islands, decisions about possible migration rules among family islands were included. From among 60 possible strategies, genetic improvement is maximized for the first five to 10 cycles using genomic selection and a hub network mating design, where the hub parents with the largest selection metric make large parental contributions. It also requires that the breeding populations be organized as fully connected family islands, where every island is connected to every other island, and migration rules allow the exchange of two lines among islands every other cycle of selection. If the objectives are to maximize both short-term and long-term gains, then the best compromise strategy is similar except that the mating design could be hub network, chain rule, or a multi-objective optimization method-based mating design. Weighted genomic selection applied to centralized populations also resulted in the realization of the greatest proportion of the genetic potential of the founders but required more cycles than the best compromise strategy.

Haplotype Reconstruction in Connected Tetraploid F1 Populations

In diploid species, many multiparental populations have been developed to increase genetic diversity and quantitative trait loci (QTL) mapping resolution. In these populations, haplotype reconstruction has been used as a standard practice to increase the power of QTL detection in comparison with the marker-based association analysis. However, such software tools for polyploid species are few and limited to a single biparental F1 population. In this paper, a statistical framework for haplotype reconstruction has been developed and implemented in the software PolyOrigin for connected tetraploid F1 populations with shared parents, regardless of the number of parents or mating design. Given a genetic or physical map of markers, PolyOrigin first phases parental genotypes, then refines the input marker map, and finally reconstructs offspring haplotypes. PolyOrigin can utilize single nucleotide polymorphism (SNP) data coming from arrays or from sequence-based genotyping; in the latter case, bi-allelic read counts can be used (and are preferred) as input data to minimize the influence of genotype calling errors at low depth. With extensive simulation we show that PolyOrigin is robust to the errors in the input genotypic data and marker map. It works well for various population designs with ≥ offspring per parent and for sequences with read depth as low as 10x. PolyOrigin was further evaluated using an autotetraploid potato dataset with a 3 × 3 half-diallel mating design. In conclusion, PolyOrigin opens up exciting new possibilities for haplotype analysis in tetraploid breeding populations.

Exploiting heterosis and combining ability in two-line hybrid rice

<p>Twenty hybrids were developed from crossing four environmental genic male sterile (EGMS) lines with five testers in line × tester mating design to magnitude of heterosis over better parent for grain yield and contributing traits in rice (<em>Oryza sativa </em>L.). Five hybrids ‘WTSC9059’ × ‘Sakha101’, ‘WTSC9039’ × ‘Sakha102’, ‘WTSC9059’ × ‘Sakha108’, ‘WTSC9039’ × ‘Sakha108’ and ‘WTSC9039’ × ‘Sakha101’ express superior value for number of panicles, fertility percentage, 100-grain mass, grain yield, apparent heterosis and phenotypic acceptance. The top three heterotic combinations identified for grain yield/ha were ‘WTSC9059’ × ‘Sakha101’, ‘WTSC9039’ × ‘Sakha102’ and ‘Longping’ × ‘Sakha105’ which exhibited 100.00, 71.51 and 66.61 % heterobeltiosis, respectively. The lines ‘WTSC9059’ and ‘‘Longping’’ and testers ‘Sakha101’, ‘Sakha102’ and ‘Sakha108’ was found to be good general combiner for most of the characteristics and could be extensively used in future hybrid rice breeding program. The grain yield was correlated highly significant and positive with panicle exertion, panicle mass, fertility percentage and appearance of heterosis, otherwise the negative correlation and significant was found with flag leaf area.</p>