One hundred advanced oat lines involving two checks were assessed for genetic variability and diversity based on 15 agro-morphological traits by using principal component analysis. Only four out of ...19 principal components (PCs) exhibited more than one eigen value and 71.42 % variability. PC-1 accounted for 47.28 % of overall variability followed by PC-2, which exhibited 9.05% variability while PC-3 and PC-4 accounted for 8.15% and 6.95% variability respectively. PC3 contains most of the traits that contributes significantly to the yield hence, lines from PC3 can be selected for rapid improvement of yield. Based on PC scores, genotypes JO (IS) 12-4-9, JO (IS) 12-5-5, JO (IS) 12-5- 14, JO (IS) 12-6-19, JO (IS) 12-8-2, JO (IS) 12-8-4, JO (IS) 12-8-5, JO (IS) 12-8-11 and JO (IS) 12-8-18 are the major sources of variation in the oat population and this information would be useful for selecting potential inbred lines for future oat improvement programme.
► Three testers (TZEEI 79, TZEEI 76 and TZEEI 63) were identified across environments. ► Three opposing heterotic groups were identified across research environments. ► Additive gene action is ...important in the inheritance of traits across environments. ► TZEEI 95×TZEEI 79 was identified as the potential single-cross tester. ► TZEEI 79×TZEEI 76 was the highest yielding and stable hybrid across environments.
Maize (Zea mays L.) is a major staple crop in West and Central Africa (WCA) but production is constrained by Striga hermonthica parasitism and recurrent drought in the savannas where maize yield potential is highest. Two studies were conducted for 2 years at 5 locations in Nigeria. The objective was to determine the combining ability of seven extra-early yellow-endosperm inbreds, place them into heterotic groups, identify the best testers and superior single-cross hybrids under drought, Striga infestation, optimal conditions and across environments. General combining ability (GCA) and specific combining ability (SCA) mean squares were significant for grain yield and most other traits across test environments. Mean squares for GCA were larger than those of SCA in all environments, indicating that additive gene action was more important in the inheritance of traits. Three testers (TZEEI 79, TZEEI 76 and TZEEI 63) and opposing heterotic groups (TZEEI 95, TZEEI 78, TZEEI 79), (TZEEI76, TZEEI 82) and (TZEEI 63, TZEEI 58) were identified across environments. TZEEI 79 had the highest positive GCA effects for grain yield across environments. Furthermore, TZEEI 95×TZEEI 79 was identified as the potential single-cross tester for the development of three-way and double-cross hybrids. Results of repeatability analysis showed that the managed drought test site, IKDT, was the most repeatable even though it was not very discriminating. In contrast, ZAWW had high representativeness, discriminating ability and repeatability, indicating that it was the ideal test location. The best extra-early hybrid TZEEI 79×TZEEI 63 under drought stress and TZEEI 82×TZEEI 79 under Striga infestation were comparable in yield to the best open-pollinated early check. GGE biplot analysis revealed TZEEI 79×TZEEI 76 as the highest yielding and most stable hybrid across environments. The available extra-early maize inbred lines are not only drought escaping but also possess genes for drought tolerance.
An experiment was conducted to evaluate the genetic divergence in 93 inbreds of fodder maize through genetic variability, D2 and principal component analysis. Observations were recorded on ten ...biometrical traits and a quality trait. The variability analysis revealed higher GCV and PCV for green fodder yield per plant and higher heritability coupled with high genetic advance for the traits viz., plant height, leaf length and green fodder yield per plant. Hence, the variability study indicated that the direct selection for the above traits would be effective. Diversity analysis sorted the 93 inbred into eleven clusters. In case of inter cluster distance, maximum distance was obtained between cluster VIII and X followed by cluster VI and VIII and VIII and XI indicating that these cluster pairs have a more genetic divergence and the inbreds of these clusters could be utilized in a fodder maize hybridization programme. The D2analysis suggests that the inbreds viz., GETM30, GETM84, GETM12, and GETM81 were distinct and diversified and classed as promising inbreds based on the cluster mean and divergence. These genotypes could be utilized in a fodder maize hybridization programme to obtain heterotic fodder maize hybrids apart from getting the desired segregants in later generations. According to the principle component (PC) analysis, out of 11 PC groups, four PCs recorded more than one Eigen value, which contributes 70.30% of the total variability. However, the variability for green fodder yield and its attributing traits were higher in PC1, PC2, PC3 and PC4 and hence, the inbreds that recorded higher PC scores in these components could be utilized in the further hybridization programme to enhance the biomass yield in fodder maize.
Classical cytoplasmic male sterility (PET-1) discovered by Leclercq and a few restorer lines are being utilized for commercial hybrid seed production in sunflowers over the world since 1972. The ...utilisation of a single source of male sterility results in a high level of vulnerability to biotic and abiotic stresses. The goal of this study was to identify new fertility restorers for two different cytoplasmic male sterile sources, i.e., PET-1 (COSF-6A, COSF-7A, CMS-38A, ARM- 248A) and CMS PEF (FMS-852A). Five CMS lines were crossed with newly developed drought tolerant 10 inbred lines in Line x Tester fashion and an evaluation of test cross progenies was conducted. All the inbreds were categorized into complete, partial restorers and maintainers through cytological observation. Six inbreds, viz., RGP-157, RGP-184, RGP-190, RGP-223, RGP-225 and RGP-233 behaved as restorers for all the CMS lines and restored fertility, while RGP-222 and 298R inbreds maintained sterility. The CMS line, FMS-852A was maintained by four inbreds indicating the involvement of different gene(s), while six inbreds, RGP-157, RGP-184, RGP-190, RGP-223, RGP-225 and RGP- 233 were restored its fertility. None of the inbreds behaved as partial restorers for any of the CMS lines. The fertility restoration ranged from 91.4 to 97.4 per cent in different cross combinations. In the present study, pollen fertility of up to 80 per cent was observed for the PET-1 source. However, only 60 per cent of the pollen fertility was observed for CMS fallax. From the study, it was evident that among the two CMS sources, restorers for PET-1 and PEF were available. Efforts should be made to utilize CMS PEF for the production of more productive sunflower hybrids resistant to biotic and abiotic stresses.
Sunflower (Helianthus annuus L.) is one of the most important oilseed crops grown worldwide because of its supreme oil quality and commercial importance. Assessment of diversity among inbreds is a ...vital prerequisite to select parents for a hybridization programme. Hence, in the present investigation, the genetic divergence of 29 genotypes consisting of both maintainer and restorer inbreds was studied using Mahalanobis (D2) analysis. Genotypes were grouped into eight clusters, in which cluster I was the largest with 13 genotypes. Clusters IV, VI, VII and VIII were the smallest, with one genotype each. The maximum intracluster distance was observed in cluster I followed by II. Maximum inter cluster distance was recorded between clusters II and V followed by clusters II and VII. Days to 50% flowering had the maximum contribution (32.76%) for genetic divergence. Superior mean performance for head diameter, 100 - seed weight, seed yield per plant and oil content was observed in cluster VI whereas earliness in terms of days to 50% flowering and days to maturity was observed in cluster II. Cluster VIII recorded superior mean performance for volume weight and the lowest mean plant height was observed in cluster VII. Hence, hybridization between cluster II (CMS 10B, HA 89B, RHA-1-1) and cluster V (CMS 519B, HA 430B) could create more variability in the segregating generations.
Conceptual representation of the response of absolute heterosis plasticity to traits plasticities for both genotypic groups. Both plasticities are expressed as the response (i.e., slope) to the ...environment (i.e., environmental index). ASI: anthesis-silking interval, BIOPM: aboveground biomass at physiological maturity, EGRCP: apical ear growth rate during the critical period, KNP: kernel number per plant, KW: individual kernel weight, PGRCP: plant growth rate during the critical period, PGY: plant grain yield, Pr: prolificacy.
Display omitted
•A balanced environmental index is a robust tool for phenotypic plasticity analysis.•The response to the environmental index was linear, bilinear or null depending on the trait.•A tight association exists between phenotypic and absolute heterosis plasticities.•The positive trend in mentioned association is driven by hybrids.•The relative benefit of exploiting heterosis for grain yield is not environment-dependent.
Maize grain yield is determined by genotype (G), environment (E) and G × E interaction effects that influence the expression of traits along the crop cycle. Inbreds and hybrids may differ in their responses to fluctuations in environmental conditions, determining changes in heterosis levels across environments and consequently the target environment for their evaluation. The objectives of this work were (i) to compare traits related to grain yield, aboveground biomass production and its partitioning in two contrasting genotypic groups (inbreds and hybrids) and (ii) to analyze their performance across environments for the assessment of their phenotypic plasticity as well as environmental effects on the expression of heterosis. We built a balanced environmental index based on normalized plant grain yield (BEINPGY) from 14 contrasting environments using a 6-inbred complete diallel mating design and analyzed the response of the 12 evaluated traits to this index for each genotypic group. This approach allowed us to (i) differentiate among traits with simple linear (grain yield, total biomass, kernel numbers, the anthesis-silking interval and plant reproductive efficiency), bilinear (harvest index, individual kernel weight, prolificacy and apical ear reproductive efficiency) or no response (ear and plant growth rates around flowering as well as their relationship) in phenotypic plasticity of each group to the BEINPGY, and (ii) group traits depending upon their absolute heterosis response (i.e., heterosis plasticity) to the BEINPGY, which varied in sign (positive, null or negative) depending upon the trait. There was a clear and positive relationship between absolute heterosis plasticity and traits plasticities, which was mainly driven by hybrids. Genotypic groups differed in the association patterns of traits values per se as well as of their phenotypic plasticities, indicative of the different genetic bases that determine them. The fact that percent heterosis for grain yield and other relevant secondary traits did not vary across environments, whereas heritability is expected to decrease under stressful conditions, may contribute to guide future breeding efforts aiming to develop superior hybrids with successful performance, particularly in future challenging environmental scenarios.
Vitamin A deficiency poses health risks for children, pregnant women, and nursing mothers in sub-Saharan Africa (SSA) and Southeast Asia. Provitamin A–biofortified maize varieties can contribute to ...minimizing the adverse effects of vitamin A deficiency in areas where maize is a staple food crop. Identifying suitable testers is important to breed provitamin A–biofortified hybrid maize. This study was therefore conducted to 1) assess the suitability of maize inbred lines with contrasting levels of provitamin A (one with high and one with low provitamin A concentration) to assess the combining ability of maize inbred lines in accumulating provitamin A and other carotenoids, and grain yield, 2) confirm the mode of inheritance of provitamin A and grain yield, and 3) identify promising inbred lines with desirable combining ability effects for use to develop high-yielding provitamin A–biofortified hybrids. The inbreds crossed to the two inbred testers were evaluated in four environments for the carotenoid content and eight environments for the agronomic performance. The combined analysis of variance revealed a significant genetic variation among the testcrosses for all carotenoids, grain yield, and other agronomic traits. The mode of inheritance for grain yield, other agronomic traits, provitamin A, and other carotenoids was regulated by both additive and non-additive gene effects with a prominence of additive gene effects. The high provitamin A tester that displayed positive GCA effects for β-carotene and provitamin A content, broader agronomic performance of testcrosses, and higher levels of provitamin A in testcrosses can be considered suitable for breeding programs developing provitamin A–biofortified hybrids. The inbred lines TZI2012, TZI2142, TZI2130, TZI2065-2, TZI2161, TZI2025, TZI1278, TZI1314, TZI1304, and TZI2032 with positive GCA effects for grain yield and provitamin A content could be used as parental lines to develop source population of new inbred lines and high-yielding hybrids with elevated levels of provitamin A. The best performing hybrids are promising for release as high-yielding provitamin A maize hybrids after further evaluations.
•Enhanced variation in plasticity after correction of the lowermost percentile.•Large plasticity for anthesis-silking interval, grain yield and kernel number.•Reduced plasticity for developmental ...traits and kernel weight.•Mean inbreds phenotypic plasticity had a larger variation than that of hybrids.•Lack of relationship between traits heritability and their phenotypic plasticity.
Correct characterization of heritability and phenotypic plasticity (PP) is critical for breeding purposes. The latter refers to the variation range of a trait in response to changes in the environment and has been assessed as the difference between percentiles 10th (P10) and 90th (P90) of each trait, which does not reflect below the median (P50) variations to the same extent as the above the median ones. This inconsistency may affect the classification of stable (low PP) or plastic (high PP) given to traits, as well as their relative ranking and PP relationship with heritability. The objectives of current research were to evaluate corrected PP (PPC) variation in grain yield (GY) and related secondary traits among contrasting maize genotypic groups (inbreds and hybrids) grown under contrasting water regimes (WR) and nitrogen (N) availabilities. The relationship between PPC and broad-sense heritability (H2) was also assessed. Field experiments were conducted during three (N) or seven (WR) growing seasons at two mid-latitude environments of Argentina. Measured traits were days and thermal time to 50% anthesis (A50 and TTA) and to 50% silking (S50 and TTS), the anthesis-silking interval in days (ASID) and in TT (ASITT), plant height (Ph), prolificacy (Pr), GY, kernel numbers (KN), and kernel weight (KW). Values for percentiles 10th (P10), 50th (P50) and 90th (P90) of each trait were identified for each treatment combination. P50 was set to 1, and values obtained for P10 and P90 were expressed as ratios with P50. P10 was corrected (P10C= P50 – P50/P10) to reflect the below P50 variations to the same extent as those above P50. Corrected PP was estimated as PPC= P90 - P10C. P90 values of all traits corresponded to non-stressed plots whereas P10C values corresponded to stressed plots, except for ASIs (opposite trend). A large plasticity (PPC>mean PPC) was usually verified for ASIs, GY and KN. Mean inbreds PPC had a larger variation than mean hybrids PPC (+19% for WR and +29% for N), except for GY under contrasting WR (hybrids > inbreds). A common trend across all evaluated traits was the markedly larger effect on PPC of P10C than of P90, in agreement with the predominant representation of stressful conditions by the former and in contrast to previous studies where no correction was performed on P10. Our results demonstrated the lack of relationship between H2 and PP and improved current knowledge about the importance of environment modulation on PP of most expansion-related and production traits, highlighting the relevance of the evaluated resource (water or N) as well as of the genotypic group (hybrids or inbreds) on final phenotype expression.
Historical genomics of North American maize van Heerwaarden, Joost; Hufford, Matthew B.; Ross-Ibarra, Jeffrey
Proceedings of the National Academy of Sciences - PNAS,
07/2012, Letnik:
109, Številka:
31
Journal Article
Recenzirano
Odprti dostop
Since the advent of modern plant breeding in the 1930s, North American maize has undergone a dramatic adaptation to high-input agriculture. Despite the importance of genetic contributions to ...historical yield increases, little is known about the underlying genomic changes. Here we use high-density SNP genotyping to characterize a set of North American maize lines spanning the history of modern breeding. We provide a unique analysis of genomewide developments in genetic diversity, ancestry, and selection. The genomic history of maize is marked by a steady increase in genetic differentiation and linkage disequilibrium, whereas allele frequencies in the total population have remained relatively constant. These changes are associated with increasing genetic separation of breeding pools and decreased diversity in the ancestry of individual lines. We confirm that modern heterotic groups are the product of ongoing divergence from a relatively homogeneous landrace population, but show that differential landrace ancestry remains evident. Using a recent association approach, we characterize signals of directional selection throughout the genome, identifying a number of candidate genes of potential agronomic relevance. However, overall we find that selection has had limited impact on genome-wide patterns of diversity and ancestry, with little evidence for individual lines contributing disproportionately to the accumulation of favorable alleles in today's elite germplasm. Our data suggest breeding progress has mainly involved selection and recombination of relatively common alleles, contributed by a representative but limited set of ancestral lines.
Hybrid development is basically dependent on the variability among available genetic resources. Polymorphism among the maize inbreds is essentially needed for maize hybridization. This study aimed at ...the assessment of diversity among 22 maize inbreds by 18 microsatellite markers. The study identified 187 alleles at 18 SSR loci. The amplified allele frequency per microsatellite locus was 10.4 and the highest allele per locus was 17 in SSR primer pair phi026. SSR primer set p-umc1292, phi074 and phi090 showed the lowest 6 alleles per genotype per locus. The locus phi026 showed the highest degree of gene diversity (0.92), and the locus p-umc1292 had the lowest of gene diversity (0.77) with a mean value of 0.862 among the microsatellites. At each site, the most prevalent allele varied between 0.14 (bnlg371) and 0.36. (p-umc1292). At any given locus, an average of 0.22 out of the 22 selected maize inbred lines had a common major allele. The average value of the polymorphic information content (PIC) was 0.85, within the range of 0.74 at the lowest to 0.92 at the highest. The higher PIC values of phi026 and nc013 established them to be the best markers for maize inbred lines. The UPGMA clustering generated seven distinct groups having 12.5% of similarity coefficient. The results revealed that inbred lines E10, E27, E19, E34, E35, E4, E43, E28, E11, E21, E17, E38, E25, E34, E14, E16, E39 and E3 were more diversified. These lines are promising to be used as parent materials for hybrid maize development in the future.
PDF
