Heterosis For Yield Research Articles

Enhanced grain yield in rice hybrids through complementation of fertility restoration by Rf3 and Rf4 genes as revealed by multilocation evaluation of tropical japonica derived rice (Oryza sativa) hybrids

AbstractThirty‐one tropical japonica derived Rf gene carrying rice hybrids were classified into three classes as Rf3, Rf4 and Rf3 + Rf4 hybrids. These hybrids were tested under three different mega‐environments. Between Rf3 class and both the classes of hybrids possessing Rf4 genes, significant variation for spikelet and pollen fertility and grain yield was found. The pollen fertility was five times higher among Rf4 hybrids than that of hybrids carrying Rf3 alone. Likewise, spikelet fertility among Rf4 hybrids was two times higher than that of Rf3 hybrids. Parallel grain yield increase in Rf4 hybrids was 2.4 times than in Rf3 hybrids. However, Rf3 gene was found complementing Rf4 to truncate the range of pollen and spikelet fertility. Hybrids possessing Rf3 alone exhibited partial pollen and spikelet sterility, and significant negative standard heterosis for grain yield. The high yielding hybrid, “HYB36” carrying both the Rf genes was found to be widely adapted. The present study established that Rf4 gene is essential either alone or in combination with Rf3 for fertility restoration to achieve enhanced grain yield in WA‐CMS based hybrids.

English

Maize (Zea mays L.) is one of the cereals that provide calorie requirements in the majority of Ethiopians diet. The national average maize yield in Ethiopia is low and thus knowledge of combining ability and heterosis is a prerequisite to develop high yielding maize varieties. The objective of the present study is to estimate combining abilities of double haploid (DH) maize inbred lines for grain yield and related agronomic traits, and to identify crosses with higher standard heterosis. A total of 36 diallel crosses generated by crossing nine maize DH lines using half diallel mating scheme and four standard checks were studied for different desirable agronomic traits during 2017 cropping season at Ambo and Kulumsa Agricultural Research Centers. The genotypes were evaluated in alpha lattice design replicated twice in both locations. Analyses of variances showed significant mean squares due to crosses for most traits studied. The highest grain yields were obtained from crosses L1 x L3, L3 x L8, L4 x L8 and L8 x L9. GCA mean squares were significant for all studied traits, while SCA mean squares were significant only for grain yield, days to anthesis, ear per plant and ear diameter. Relatively larger GCA over SCA variances were observed in the current study for most studied traits revealing the predominance of additive gene action in controlling these traits. Of the DH inbred lines, L3 and L8 were the best general combiners for grain yield, and hence are promising parents for hybrid development. Inbred lines  L2, L4, L6, L7 and L8 were good combiners for earliness whereas, L1, L2 and L6 showed negative and significant GCA effects for plant and ear height. In this study, none of the crosses showed positive and significant standard heterosis for grain yield.   Key words: Combining ability, general combining ability, highland maize, standard heterosis, specific combining ability.

Heterosis and inbreeding depression for yield and its components traits in barley (Hordeum vulgare)

Heterosis and inbreeding depression was analysed using a set of diallel crosses involving 10 diverse parents (excluding reciprocals). Heterosis over standard parent for grain yield per plant ranged from -9.65–45.45 (%) and -14.78–12.05 (%) under normal and late sown conditions, respectively and heterosis over better-parent for grain yield per plant ranged from -26.43–70.77(%) and -32.16–12.05(%) respectively. Nature and magnitude of heterosis and inbreeding depression varied across crosses, characters as well as environments. Considering the very high degree of heterosis in desirable direction, the importance of non-additive components of genetic variance was observed for yield and most of the yield contributing components. Cross II (K 603 × Azad) and cross IV (RD 2618 × PL 708) revealed better specific cross combinations to be used for heterosis. The study revealed good scope for commercial exploitation of heterosis as well as isolation of pure lines among the progenies of heterotic F1 for improvement of yield levels in barley.

Heterosis for yield and yield contributing traits in sunflower (Helianthus annuus L.)

The present experiment involved four CMS lines and six testers which were crossed in line x tester fashion toestimate the heterosis for seed yield and yield contributing traits in sunflower. Resulting 24 F1 hybrids were evaluated in two replications in RBD along with two commercial checks LSFH-171 and LSFH-35. Range of standard heterosis in 24 F1 hybrids over check LSFH-171 was from -6.42 to 31.74 and over the other check LSFH- 35 it was from -13.56 to 13.56 for oil content. Extent of heterosis for seed yield in hybrids ranged from -20.51 to37.18 over LSFH-171 and from -6.06 to 62.12 over LSFH-35. Hybrid PET 89-1 x EC-601951 exhibited significantnegative heterosis for early flowering and days to maturity over both checks. Based on per se performance, hybrids CMS 234A x EC-601957, CMS-234A x EC-601951, CMS-243A x EC-601957, PET-89-1A x EC-601951 and CMS234A x EC-623008 were superior for oil content and most of the yield contributing traits indicating them to be promising new combinations for hybrid development.

Genetic studies on high lignan content in sesamum (Sesamum indicum L.)

Lignans especially sesamin and sesamolin are secondary metabolites having therapeutic value. The sesamegermplasm were screened for lignan content. A set of four low lignan and four high lignan lines were crossed in Line x Tester mating design. Based on the evaluation of F1s, the genotype KRISHNA was identified as good combiner and the cross (JLS 57 x PKDS 12) showed high sca effects. The crosses (JLS-57 x GUN-18), (KRISHNA x GUN- 18), (JLS 57 x PKDS 12) and (KRISHNA x PKDS-12) showed high heterosis for yield and lignan content.

Performance of newly developed sunflower inbred lines for yield and yield contributing traits under rainfed condition

The present investigation was carried out at ICAR-Indian Institute of Oilseeds Research, Hyderabad. The materialconsisted of 25 newly developed mono and multi headed restorer lines. The data for agronomic and yield traits was recorded. The genotypes, COSF-6B, COSF-7B, RGP-11-P1-S2, RGP-58-P4-S1-1 and RGP-46-P3 were identified as the most important genotypes for different traits and should be utilized in hybridization program to realize high heterosis for yield and yield contributing traits.

Estimation of heterosis for yield and its components under normal and sodic soil in barley (Hordeum vulgare L.)

Manipulation of heterosis is considered to be a vital approach to enhance the yield potential of barley and is as accepted to be a safe strategy to overcome barriers in barley yield. Thirteen diverse Indian genotypes were crossed to obtain a series of crosses to estimate the level of heterosis and heterobeltiosis among F1 hybrids along with their parents under two contrasting environments: normal and sodic soil. Estimates revealed a significant relationship between the mean performance of F1 hybrids and their parents under sodic stress regime only. The presence of significant heterosis for grain yield was also accompanied by heterosis for yield components, such as days to 50% flowering, plant height, number of effective tillers /plant, number of spikelets /spike, number of grains/ spike, days to maturity,1000- grain weight, biological yield / plant, grain yield / plant and harvest index. The cross NDB 1245 X NDB 943 was an elite cultivar and showed significant heterobeltiosis. The study suggests that the obtained hybrids surpassed their better parents’ effects, indicative of commercial heterosis, and are thus candidates for the commercial production of hybrid barley.

Extent of heterosis for grain yield and its contributing traits in rabi sorghum [Sorghum bicolor (L.) Moench

Heterosis has been successfully exploited commercially in kharif sorghum [Sorghum bicolor (L.) Moench]. However, the progress in rabi sorghum is restricted and there is a need for critical studies heterosis and combining ability involving diverse sources of germplasm and landraces. A total of 50 sorghum hybrids were derived by line × tester design using two male sterile lines viz., M 31-2A and 104A, as testers and were assessed for Extent of heterosis for grain yield and its contributing traits in rabi 2019-20. Among 50 crosses 13 exhibited significant standard heterosis for yield over popular variety M 35-1 (check). The crosses M 31-2A × IS 32439 (65.28 g) and M 31-2A × IS 11619 (60.83 g) recorded maximum heterosis for grain yield per plant. The cross M 31-2A × IS 4581 exhibited maximum heterosis for 100 seed weight followed by M 31-2A × IS 30451, 104A × IS 30451 and 104A × IS 4581. for panicle length, the cross 104A × IS 602 exhibited highest significant positive standard heterosis over the checks M 31-2A, BJV 44 and PKV Kranti.

Genetic Analysis of Morphological Traits in Wheat Hybrids Based on the Additive-Dominance Model

Present study carried out in a randomized complete block design with three replications for determining additive, dominance and cytoplasmic effects on inheritance of yield and some of agro-morphological traits in bread wheat. The highest value of grain yield (265.5 g m–1) was obtained in p6. Dominance variance was larger than additive variance for grain-filling period (GFP), plant height (PH), spike length (SL), flag leaf exit (FLE), canopy temperature (CT), early growth vigor (EGV), grain length (GL) and thousand-grain weight (TGW). Whereas, the additive variance was larger than dominance one for days to heading (DH), days to maturity (DM), peduncle length (PL), SPAD and grain yield (GY). Therefore, for these traits selection in early breeding generations could be effective to bring positive changes in these traits. There were significantly positive additive effects (A) of P1 on GFP, CT, GL and TGW; of P3 on DH and DM; P4 on PL, FLE, SPAD and GY and of P6 on PH, SL and EGW. The crosses containing g3 × g4, g4 × g5 and g4 × g6 were indicated positive and significant heterosis for grain yield. P6 were desirable parent for reducing days to heading and maturity and increasing plant height, spike length and early growth vigor.

Heterosis, combining ability and stability analysis for Bioenergy traits in sweet sorghum [Sorghum bicolor (L.) Moench

An investigation on assessment of heterosis, combining ability and G×E interaction in respect of ethanol yield and its attributing traits was carried out with 30 test hybrids of sweet sorghum developed by crossing five (5) low-sugar female lines with six (6) high-sugar male lines in Line x Tester mating design during kharif season of 2010 over three locations. The hybrids viz., NSS 1007A × CSV 19SS and RS 1220A × SSV 74 are highly suitable for heterosis breeding as they exhibited significant positive standard heterosis for ethanol yield and its contributing traits. The parents, RS 1220B, CSV 19SS and SSV 74 were found to be good general combiners, while the cross combinations viz., NSS 1007A × CSV 19SS and NSS 1016A × SSV 84 showed good specific combining ability coupled with high per se performance for ethanol yield hence highly suitable for heterosis breeding. Based on stability, the hybrids viz., NSS 8A × SSV 84 and NSS 1007A × CSV 19SS for ethanol yield, juice yield and total biomass were found to be stable with well adaptation to all environments whereas NSS 8A × CSV 19SS showed specific adaptation to favourable environments for the traits like ethanol yield, juice yield, total soluble solids and total sugar index while NSS 8A × SSV 74 showed specific adaptation to unfavourable environments for ethanol yield. The hybrid NSS 1007A × CSV 19SS exhibited high mean, significant positive standard heterosis and sca effects along with bi near to unity and non-significant deviation from regression.

Combining ability and heterosis studies in tomato (Solanum lycopersicum L.) for quality traits and yield

Thirty crosses were done in tomato using ten genotypes as lines and three genotypes as testers in line × tester mating design. All the crosses along with parents were evaluated for combining ability and heterosis for quality traits and yield. H-86 was the good general combiner for titrable acidity, ascorbic acid, lycopene and shelf life, Azad T-5 was the good general combiner for TSS. Best specific combiner for TSS and fruit yield was Fla 7171 × Sel-7. A perusal of GCA/SCA variances revealed that SCA variances were of higher magnitude than GCA variances for yield, ascorbic acid and titrable acidity. It shows the preponderance of non-additive gene action governing these traits. For the fruit shape index, TSS, lycopene and shelf life, the GCA variance was of higher magnitude than the SCA variance, indicating the predominant role of additive gene action. The ratio of σ2gca / σ2sca is less than unity for all characters except fruit shape index, titrable acidity and ascorbic acid which also indicated the preponderance of non additive genetic variance. Best heterotic combination, for fruit yield and TSS was Fla 7171 × Sel-7, for fruit shape index was H-24 × Azad T-5, for ascorbic acid was Kashi Amrit × Kashi Sharad, for lycopene was H-86 × Azad T-5 and for shelf life was Floradade × Azad T-5. High heritability (>60%) combined with high genetic advance (>20%) was observed for shelf life, fruit yield, lycopene, TSS which indicates that these traits can be improved by simple selection.

Estimation of heterosis and combining abilities of U.S. winter wheat germplasm for hybrid development in Texas

AbstractHybrid wheat (Triticum aestivum L.) offers promises to break the yield stagnation in global wheat productivity as a result of heterosis. But, for this promise to be realized, the level of heterosis must be adequate. To test this, elite winter wheat lines from the breeding programs of the University of Nebraska–Lincoln (UNL) and Texas A&M University (TAMU) were crossed in a 25‐by‐25 full‐diallel design using a chemical hybridizing agent (CHA) to produce experimental hybrids. These hybrids were planted in a modified augmented design with commercial checks and parents at McGregor, TX, in 2016 (n = 612) and Greenville and Bushland, TX, in 2017 (n = 470) to evaluate for yield heterosis and combining ability. A subset of hybrids (n = 333) were repeated between years. The effect of field heterogeneity in grain yield was corrected by spatial modelling in ASReml‐R. Commercial heterosis ranged from −78.3 to 20.4% in 2016 and −32.9 to 6.2% in 2017. High‐parent heterosis (HPH) ranged from −70.4 to 54.3% in 2016 and −26.9 to 29.2% in 2017. General combining ability (GCA) variance was significantly higher than zero, whereas specific combining ability (SCA) variance was not. Significant maternal effect was identified in some crosses tested by computing reciprocal effects between crosses and estimating variances. This indicates that most of the heterosis is due to additive rather than dominance effect. These results suggest exploitation of GCA for higher yield while underscoring the need for development of heterotic pools to maximize SCA and dominance effects.

Heterosis analysis and underlying molecular regulatory mechanism in a wide-compatible neo-tetraploid rice line with long panicles

BackgroundNeo-tetraploid rice, which is a new germplasm developed from autotetraploid rice, has a powerful biological and yield potential and could be used for commercial utilization. The length of panicle, as a part of rice panicle architecture, contributes greatly to high yield. However, little information about long panicle associated with heterosis or hybrid vigor is available in neo-tetraploid rice.ResultsIn the present study, we developed a neo-tetraploid rice line, Huaduo 8 (H8), with long panicles and harboring wide-compatibility genes for pollen and embryo sac fertility. All the hybrids generated by H8 produced significant high-parent yield heterosis and displayed long panicles similar to H8. RNA-seq analysis detected a total of 4013, 7050, 6787 and 6195 differentially expressed genes uniquely belonging to F1 and specifically (DEGFu-sp) associated with leaf, sheath, main panicle axis and spikelet in the two hybrids, respectively. Of these DEGFu-sp, 279 and 89 genes were involved in kinase and synthase, and 714 cloned genes, such as GW8, OsGA20ox1, Ghd8, GW6a, and LP1, were identified and validated by qRT-PCR. A total of 2925 known QTLs intervals, with an average of 1~100 genes per interval, were detected in both hybrids. Of these, 109 yield-related QTLs were associated with seven important traits in rice. Moreover, 1393 non-additive DEGs, including 766 up-regulated and 627 down-regulated, were detected in both hybrids. Importantly, eight up-regulated genes associated with panicle were detected in young panicles of the two hybrids compared to their parents by qRT-PCR. Re-sequencing analysis depicted that LP (a gene controlling long panicle) sequence of H8 was different from many other neo-tetraploid rice and most of the diploid and autotetraploid lines. The qRT-PCR results showed that LP was up-regulated in the hybrid compared to its parents at very young stage of panicle development.ConclusionsThese results suggested that H8 could overcome the intersubspecific autotetraploid hybrid rice sterility caused by embryo sac and pollen sterility loci. Notably, long panicles of H8 showed dominance phenomenon and played an important role in yield heterosis, which is a complex molecular mechanism. The neo-tetraploid rice is a useful germplasm to attain high yield of polyploid rice.

Comparative transcriptome analysis of inbred lines and contrasting hybrids reveals overdominance mediate early biomass vigor in hybrid cotton

BackgroundHeterosis breeding is the most useful method for yield increase around the globe. Heterosis is an intriguing process to develop superior offspring to either parent in the desired character. The biomass vigor produced during seedling emergence stage has a direct influence on yield heterosis in plants. Unfortunately, the genetic basis of early biomass vigor in cotton is poorly understood.ResultsThree stable performing F1 hybrids varying in yield heterosis named as high, medium and low hybrids with their inbred parents were used in this study. Phenotypically, these hybrids established noticeable biomass heterosis during the early stage of seedling growth in the field. Transcriptome analysis of root and leaf revealed that hybrids showed many differentially expressed genes (DEGs) relative to their parents, while the comparison of inbred parents showed limited number of DEGs indicating similarity in their genetic constitution. Further analysis indicated expression patterns of most DEGs were overdominant in both tissues of hybrids. According to GO results, functions of overdominance genes in leaf were enriched for chloroplast, membrane, and protein binding, whereas functions of overdominance genes in root were enriched for plasma membrane, extracellular region, and responses to stress. We found several genes of circadian rhythm pathway related to LATE ELONGATED HYPOCOTYL (LHY) showed downregulated overdominant expressions in both tissues of hybrids. In addition to circadian rhythm, several leaf genes related to Aux/IAA regulation, and many root genes involved in peroxidase activity also showed overdominant expressions in hybrids. Twelve genes involved in circadian rhythm plant were selected to perform qRT-PCR analysis to confirm the accuracy of RNA-seq results.ConclusionsThrough genome-wide comparative transcriptome analysis, we strongly predict that overdominance at gene expression level plays a pivotal role in early biomass vigor of hybrids. The combinational contribution of circadian rhythm and other metabolic process may control vigorous growth in hybrids. Our result provides an important foundation for dissecting molecular mechanisms of biomass vigor in hybrid cotton.

Variation for heterodimerization and nuclear localization among known and novel oil palm SHELL alleles.

Oil palm breeding involves crossing dura and pisifera palms to produce tenera progeny with greatly improved oil yield. Oil yield is controlled by variant alleles of a type II MADS-box gene, SHELL, that impact the presence and thickness of the endocarp, or shell, surrounding the fruit kernel. We identified six novel SHELL alleles in noncommercial African germplasm populations from the Malaysian Palm Oil Board. These populations provide extensive diversity to harness genetic, mechanistic and phenotypic variation associated with oil yield in a globally critical crop. We investigated phenotypes in heteroallelic combinations, as well as SHELL heterodimerization and subcellular localization by yeast two-hybrid, bimolecular fluorescence complementation and gene expression analyses. Four novel SHELL alleles were associated with fruit form phenotype. Candidate heterodimerization partners were identified, and interactions with EgSEP3 and subcellular localization were SHELL allele-specific. Our findings reveal allele-specific mechanisms by which variant SHELL alleles impact yield, as well as speculative insights into the potential role of SHELL in single-gene oil yield heterosis. Future field trials for combinability and introgression may further optimize yield and improve sustainability.

Conversion of partial restorer Swarna into restorer by transferring fertility restorer Rf gene(s) through marker assisted back cross breeding (MABB) in rice

The major constraints in hybrid rice breeding are availability of limited number of parental lines with specific desirable traits and lower frequency of restorers among elite breeding lines. The popular, high-yielding mega-rice variety Swarna, has been identified to be a partial restorer (as it has only one of major fertility restorer genes, Rf4) and hence cannot be utilized directly in the hybrid rice breeding. To convert the partial restorer to complete restorer, a cross was made between Swarna and a stable restorer KMR3R possessing Rf3 and Rf4 genes and developed BC1F5 and BC2F4 populations by marker-assisted back cross breeding (MABB). The SSR marker DRRM-RF3-10 linked to Rf3 gene located on chromosome 1, clearly distinguished restorers from partial restorers. All the improved lines of Swarna possessing Rf3 and Rf4 genes showed complete fertility restoration in test crosses with higher grain yield heterosis. Few rice hybrids developed by using converted restorers were evaluated in multi location testing under the All India Co-ordinated Rice Improvement Project (AICRIP). The results indicated that new rice hybrids expressed higher heterosis with matching grain quality attributes like Swarna. This study provides significantly novel and relevant restorers to enhance and economize future hybrid rice breeding programs.

Identification of heterotic groups in South-Asian-bred hybrid parents of pearl millet.

Pearl millet breeding programs can use this heterotic group information on seed and restorer parents to generate new series of pearl millet hybrids having higher yields than the existing hybrids. Five hundred and eighty hybrid parents, 320 R- and 260 B-lines, derived from 6 pearl millet breeding programs in India, genotyped following RAD-GBS (about 0.9 million SNPs) clustered into 12 R- and 7 B-line groups. With few exceptions, hybrid parents of all thebreeding programs were found distributed across all the marker-based groups suggesting good diversityin these programs. Three hundred and twenty hybrids generated using 37 (22 R and 15 B) representative parents, evaluated for grain yield at four locations in India, showed significant differences in yield, heterosis, and combining ability. Across all the hybrids, mean mid- and better-parent heterosis for grain yield was 84.0% and 60.5%, respectively. Groups G12 B × G12 R and G10 B × G12 R had highest heterosis of about 10% over best check hybrid Pioneer 86M86. The parents involved in heterotic hybrids were mainly from the groups G4R, G10B, G12B, G12R, and G13B. Based on the heterotic performance and combining ability of groups, 2 B-line (HGB-1 and HGB-2) and 2 R-line (HGR-1 and HGR-2) heterotic groups were identified. Hybrids from HGB-1 × HGR-1 and HGB-2 × HGR-1 showed grain yield heterosis of 10.6 and 9.3%, respectively, over best hybrid check. Results indicated that parental groups can be formed first by molecular markers, which may not predict the best hybrid combination, but it can reveal a practical value of assigning existing and new hybrid pearl millet parental lines into heterotic groups to develop high-yielding hybrids from the different heterotic groups.

Gene action and heterosis for yield and kernel quality traits in experimental hybrids in sweet corn relevant for Indian conditions

Gene action and heterosis for yield and kernel quality traits in experimental hybrids in sweet corn relevant for Indian conditions

Heterosis for yield and its contributing traits in wheat

Heterosis for yield and its contributing traits in wheat

Studies on heterosis, combining ability and gene action for earliness, yield and yield components in sponge gourd

Studies on heterosis, combining ability and gene action for earliness, yield and yield components in sponge gourd