Inbred lines generated from 10 maize population developed between 1979 and 2008 were used to investigate the inbreeding depression of tropical maize varieties developed at different breeding eras and evaluated in (optimal and stressed) condition. Across all the environments used for this study, estimates of inbred depression (I) for grain yield which ranged from 15.63% for optimum environment to 35.85 under stem borer infestation, showed differences in the severity of the effects of practicing inbreeding in each of the populations and the different environments. The highest values of inbreeding depression for grain yield were recorded under stem borer infestation. The effect of inbreeding was the most severe for var. DMR-LSR-W under borer infestation and least for DMR-LSR-Y in stress free environment. This is an indication that the responses of the maize populations to inbreeding as well as the rate of attaining homozygosity differed with environments. Across the four different environments under which the genotypes were evaluated, average inbreeding depression for grain yield were greater relative to other traits considered which should be expected since grain yield is a quantitatively inherited trait, governed by many genes each with minor effects.
Development of Provitamin A quality protein maize (PVA-QPM) conferring resistance to maize streak virus (MSV) would reduce the prevalence of the disease, alleviate malnutrition and increase food security in sub-Saharan Africa. This study was conducted to (i) evaluate early maturing PVA-QPM inbreds and their derived testcross hybrids for grain yield, MSV-resistant, carotenoids, and tryptophan contents, (ii) estimate the combining ability of the MSV-resistant PVA-QPM testcrosses for all traits. Five improved open-pollinated MSV resistance cultivars and five early maturing PVA-QPM inbreds were crossed in a half-diallel fashion without reciprocals. The derived forty-five F1 topcrosses, ten parental materials, and two commercial hybrids that served as controls were tested at the Lower Niger River Basin Development Authority in Oke-Oyi, Nigeria, during rain-fed of the year 2019 and 2020. The PVA-QPM inbreds from TZEIORQ 13, TZEIORQ 29, and TZEQI 82 that were crossed with MSV resistance AK-9528-DMRSR and Pop 28 SR appeared potentially useful combinations for enhancing grain yield, MSV-resistant, carotenoids, and tryptophan contents, Testcrossed TZEQI 82 × AK-9528-DMRSR POP 28 SR, TZEQI 82 × ACR. 91 SUWAN-1-SR C1 and TZEQI 82 × IK.91 TZL COMP 3-Y C1 were most outstanding for all measured grain yield and nutrient contents. Additive genetic effects were preponderant over non-additive genetic effects under artificial infection of MSV disease. These three promising MSV resistance PVA-QPM hybrids should be evaluated under on-farm multiplication trials for stability performance and adaptation to reduce malnourishment and food self-sufficiency in SSA. Also, further researches on genomic analyses of the superior testcrosses are desirable.
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Morphological variation was investigated among 31 maize landrace accessions collected from the fields of various farmers in South Sudan by examining 7 quantitative agronomic characteristics. A significant positive correlation was found between days to tasseling (DT) and days to silking (DS), between plant height (PH) and ear height (EH) and stem width (SW), and between EH and SW and leaf length (LL). First and second principal components accounted for 69% of the total variance (40.9% and 28.6%, respectively). PH, EH, SW, LL, and leaf width (LW) were clearly characterized in a positive direction on the first axis. DT and DS were clearly characterized in a positive direction on the second axis. A scatter plot based on phenotypic data revealed the existence of 3 groups based on the most discriminating characteristics: Group I included 5 maize landrace accessions, Group II comprised 14 maize landrace accessions, and Group III included 10 maize landrace accessions. In principal component analysis, generally the investigated genotypes were not clearly grouped into their geographical origins owing to a weak geographic relationship among the accessions. In conclusion, even though the morphological characterization studies were conducted in the South Korean climate, this study revealed significant phenotypic variation among the explored maize landrace accessions collected from South Sudan. Therefore, this information about phenotypic divergence may be very useful for future breeding research programs as well as for genetic improvement of South Sudan maize accessions.
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Maize is a major staple food and source of income for over 90% of the population in South Sudan however, average yield is very low (0.5-0.9 t/ha). Little research has been done on maize improvement in the country and farmers mainly depend on local and unimproved cultivars. Identification and release of adapted and high yielding hybrids may elevate average maize yield (t/ha) among the resource-poor farmers in the country. Improved maize hybrids from the region have not been tested under South Sudanese environments.
Objective
s of the study were to: (i) determine genotype by environment interactions among some regional maize genotypes; (ii) estimate genetic components and heritability for yield performances; and (iii) identify high yielding maize hybrids adapted to agroecologies of South Sudan. At least 48 maize genotypes including elite hybrids and open-pollinated varieties (OPV) adapted across sub-Saharan Africa and two local cultivars collected from local farmers in South Sudan were evaluated across five locations within greenbelt and ironstone plateau agro-ecologies over three years (2013-2015). Experiments were set up in a 12 × 4 alpha lattice design with 2 replications. Standard agronomic practices were followed and data recorded on yield traits and resistance to major diseases. Across locations and years analysis revealed significant differences among genotypes due to genotype and genotype × environment interactions (
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Drought is one of the major abiotic factors that have a serious effect on the production of cereals crops including maize, which is grown widely in the world. Screening based on drought facilitates selection of inbred lines and an understanding of drought-tolerant traits. The effect of drought stress and rescue after stress on maize inbred lines was investigated in this study. Different plant growth attributes namely plant height, leaf area and weight, stem weight, root length, shoot and root fresh and dry weight, and total leaf chlorophyll content were measured. Six flint inbred lines (FLD 12, FLD 23, FLD 24, FLD 33, FLD 35, and FLD 37) were screened as drought-tolerant lines, whereas another six flint inbred lines (FLD 01, FLD 13, FLD 16, FLD 18, FLD 29, and FLD 31) were screened as drought susceptible lines. Growth attributes under different drought conditions were subjected to a correlation test and analysis of variance and showed highly significant relationships with each other. The drought effect differed with different inbred lines, indicating a wide variability of drought response at the early growth stage of maize plants. The results obtained from this study will be useful for selecting maize inbred lines in future breeding programs for enhancing drought tolerance.
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We selected 68 Chinese maize inbred lines to understand the genetic diversity, population structure, and marker-trait associations for eight agronomic traits and 50 simple sequence repeats (SSRs) markers. In this study, effective traits, such as days of anthesis (DA), days of silking (DS), ear height (EH), plant to ear height ratio (ER), plant height (PH), and leaf width (LW) were divided into PC1 and PC2 by PCA analysis for maize inbred lines. Genetic diversity analysis revealed a total of 506 alleles at 50 SSR loci. The mean number of alleles per locus was 10.12. The averages of genetic diversity (GD) and polymorphic information content (PIC) values were 0.771 and 0.743, respectively. Based on a membership probability threshold of 0.80, the population structure revealed that the total inbred lines were divided into three major groups with one admixed group. A marker-trait association using Q + K MLM showed that nine SSR markers (bnlg1017, umc2041, umc2400, bnlg105, umc1229, umc1250, umc1066, umc2092, and umc1426) were related with seven agronomic traits. Among these SSR markers, eight SSR markers were associated with only one agronomic trait (DA, DS, ER, LL, LW, PH, and ST), whereas one SSR marker (umc1229) was associated with two agronomic traits (DA and ST). These results will help in optimizing the choice of inbred lines for cross combinations, as well as in selecting markers for further maize breeding programs.
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We evaluated genetic diversity and population structure in 32 Canadian maize inbred lines and performed association analysis for five agronomical traits and 50 simple sequence repeat (SSR) markers. Genetic diversity analysis revealed a total of 381 alleles at the 50 SSR loci. The average number of alleles per locus was 7.6. The average genetic diversity and polymorphic information content values were 0.709 and 0.676, respectively. The average major allele frequency was 0.414. Population structure analysis indicated that these maize inbred lines were comprised of four major groups and one admixed group based on a membership probability threshold of 0.80. A general linear model showed 20 marker-trait associations involving 12 SSR markers associated with the four agronomic traits except for leaf length. For these marker-trait associations, phi056, mmc0022, bnlg1621, bnlg1695, phi116, and bnlg1028 were associated with only one trait. The other nc005, bnlg1012, phi065, and umc1982 were associated with two traits. Two SSR markers, mmc0111 and umc1038, were associated with three traits. These results will help in optimizing the choice of parents for crossing combinations, as well as in selecting markers for marker-assisted selection for maize improvement.
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There is a growing preference for using doubled haploids (DHs) in maize breeding programs because they reduce the time required to generate and evaluate new lines to 2 years or less. However, there is an urgent need for efficient techniques that accurately discriminate between haploid and diploid maize kernels. Here, we investigate the effects of several hormones and chemicals on the germination of haploid and diploid maize kernels, including auxin, cytokinin, ethylene, abscisic acid (ABA) biosynthesis inhibitor (fluridone), ABA catabolism inhibitor (diniconazole), methyl jasmonate (MeJA), and NaCl. Ethylene effectively stimulated the germination of both haploid and diploid maize kernels. The ABA biosynthesis inhibitor fluridone, the ABA catabolism inhibitor diniconazole, and MeJA selectively stimulated the germination of haploid maize kernels. By contrast, gibberellin, 1-naphthaleneacetic acid (NAA), kinetin, and NaCl inhibited the germination of both haploid and diploid maize kernels. These results indicate that the germination of haploid maize kernels is selectively stimulated by fluridone and diniconazole, and suggest that ABA-mediated germination of haploid maize kernels differs from that of diploid maize kernels and other plant seeds.
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Maize (
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Single nucleotide polymorphisms (SNPs) are abundantly and evenly distributed throughout the genomes of most plant species. These markers have become popular for use in genetic research in many crops. SNP markers can be used to screen maize cultivars rapidly during the early growth stages. In this study, to develop additional SNP markers for maize, we chose 20 SNP sites per chromosome from the maizeGDB website (
On August 2, 1999, the typhoon “Olga” with the maximum wind speed of 19.2 m/s hit the Korean peninsula and caused considerable damage to crops. Regional yield trials were at tasseling stage and were affected by the typhoon. After the storm, almost all the plants were root-lodged. This provided a rare chance to study the relationship between recovery from the lodging and reduction of grain yield in maize. Three check cultivars were examined for angle of lodging, grain yield, yield components, plant height and ear height. Six levels of leaning were classified. Plants leaning less than 10° from the vertical were considered as non-lodged. Average reduction in grain yield across five levels of lodging was 29.2% with the mean of 46.1°. The reductions of three hybrids were 25% for Suwon 19, 39.5% for Pioneer 3525 and 27.4% for DeKalb 689.
objective
in Korea.
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