[Show abstract][Hide abstract] ABSTRACT: Rice black-streaked dwarf virus (RBSDV) is an economically important virus that causes maize rough dwarf disease and rice black-streaked dwarf disease in East Asia. To study RBSDV variation and recombination, we examined the segment 9 (S9) sequences of 49 RBSDV isolates from maize and rice in China. Three S9 recombinants were detected in Baoding, Jinan, and Jining, China. Phylogenetic analysis showed that Chinese RBSDV isolates could be classified into two groups based on their S9 sequences, regardless of host or geographical origin. Further analysis suggested that S9 has undergone negative and purifying selection.
Archives of Virology 01/2015; 160(4). DOI:10.1007/s00705-014-2291-0 · 2.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Maize (Zea mays L.) populations are potential sources of favorable alleles absent in parental inbred lines to improve elite hybrids. The maize hybrid Zhengdan 958 has been hampered by the lack of favorable new alleles for improving yield and commodity quality. In the present study, 16 testcrosses made by using eight synthetic populations as the donors and the two parental lines of Zhengdan 958 as the receptors were evaluated in 2009 and 2010 at Shunyi, Beijing and Xinxiang, Henan Province for grain yield and test weight. Four genetic parameters were used to determine the breeding potential of eight synthetic populations as the donors to improve the target hybrid. Several synthetic populations were identified as the potential sources of favorable alleles absent in the target hybrid for each trait evaluated. The two most promising germplasms, WBMC-4 and Shanxi Syn3, had the potential for simultaneously improving grain yield and test weight of the target hybrid, which could be used to improve the parental lines Zheng 58 and Chang 7-2, respectively, and further broaden the germplasm base of Chinese heterotic groups PA and Sipingtou.
[Show abstract][Hide abstract] ABSTRACT: Introgression of exotic maize (Zea mays L.) germplasm is an effective approach to broadening the genetic base of Chinese germplasm. America is the center of maize origin and germplasm diversity. By analyzing general combining ability effects and heterosis responses among maize populations from the U.S., International Maize and Wheat Improvement Center (CIMMYT), and Brazil studied by different authors, 24 elite maize populations from America region, including eight U.S. populations, eight CIMMYT populations, and eight Brazilian populations, were identified as having high potential in China. Based on adaptation improvement, we suggest to introgress BSSS(R)C10, BS10(FR)C14, BS13(S)C9, BSK(HI)C8 Syn 3, BR106, Pop44(C8), and Pop45(C3) into Chinese heterotic group A, and introgress BS11(FR)C14, BS16(S)C3 Syn 2, BS29(R)C3, BSCB1(R)C14, BR105, and Pop42(C4) into Chinese heterotic group B by forming semi-exotic populations or pools, respectively, in order to broaden the Chinese germplasm base.
[Show abstract][Hide abstract] ABSTRACT: Mo17 and SH15, two head smut resistant inbred lines as donor parents were chosen to produce BC3F1 and BC4F2 populations of Huangzao4 ×(Huangzao4×Mo17) and Chang7-2 ×(Chang7-2×SH15) with two susceptible inbred lines Huangzao4 and Chang7-2 as recurrent parents, respectively. These populations were evaluated for head smut resistance with artificial inoculation under field condition. The disease incidence for BC4F2 populations of Huangzao4 ×(Huangzao4×Mo17) was higher than that of BC3F1 population. The disease incidence was found different for the BC4F2 populations of Huangzao4 ×(Huangzao4×Mo17) and Chang7-2 ×(Chang7-2×SH15). The resistant individuals were genotyped by SSR markers on maize bins 2.09 and 3.04. The number of donor introgrssion segments in BC4F2 resistant plants was becoming less than that in BC3F1, and also was different in different populations. Using linkage disequilibrium analysis, two major QTL for head smut resistance were identified, each on bin 2.09 and bin 3.04, with linked markers umc2077 and phio53\bnlg1965, respectively. The results obtained provided both useful genetic information and materials for QTL mapping and marker assisted selection for head smut resistance in maize.
[Show abstract][Hide abstract] ABSTRACT: Maize rough dwarf disease (MRDD) is a worldwide viral disease and causes significant yield losses in maize (Zea mays L.) production. In this study, we mapped and characterized quantitative trait loci (QTL) conferring resistance to MRDD using 89 F8 recombinant inbred lines derived from a cross between X178 (resistant parent) and B73 (susceptible). The population was evaluated for MRDD resistance in Baoding, Hebei Province, China (a hot spot of MRDD incidence) under natural infection in 2008 and 2009 and artificial inoculation in 2010. Genotypic variances for disease severity index (DSI) were highly significant in the population. Heritability estimates for DSI evaluation were 0.472 and 0.467 in 2008 and 2009, respectively. The linkage map was constructed using 514 gene-derived single nucleotide polymorphisms (SNPs) and 72 simple sequence repeat markers, spanning a genetic distance of 1,059.72 cM with an average interval of 1.8 cM between adjacent markers. Multiple-QTL model mapping detected a major QTL for MRDD resistance on chromosome 8, explaining 24.6–37.3% of the phenotypic variation across three environments. In 2010, an additional QTL was detected on chromosome 10, explaining 15.8% of the phenotypic variation. The major QTL on chromosome 8 and the SNP markers (SNP31, SNP548, and SNP284) co-located with the QTL peak have potential for further functional genomic analysis and use in molecular marker-assisted selection for MRDD resistance in maize.
[Show abstract][Hide abstract] ABSTRACT: Genetic factors controlling quantitative inheritance of grain yield and its components have been intensively investigated
during recent decades using diverse populations in maize (Zea mays L.). Notwithstanding this, quantitative trait loci (QTL) for kernel row number (KRN) with large and consistent effect have
not been identified. In this study, a linkage map of 150 simple sequence repeat (SSR) loci was constructed by using a population
of 500 F2 individuals derived from a cross between elite inbreds Ye478 and Dan340. The linkage map spanned a total of 1478cM
with an average interval of 10.0cM. A total of 397 F2:3 lines were evaluated across seven diverse environments for mapping
QTL for KRN. Some QTL for grain yield and its components had previously been confirmed with this population across environments.
A total of 13 QTL for KRN were identified, with each QTL explaining from 3.0 to 17.9% of phenotypic variance. The gene action
for KRN was mainly additive to partial dominance. A large-effect QTL (qkrn7) with partial dominance effect accounting for 17.9% of the phenotypic variation for KRN was identified on chromosome 7 near
marker umc1865 with consistent gene effect across seven diverse environments. This study has laid a foundation for map-based
cloning of this major QTL and for developing molecular markers for marker-assisted selection of high KRN.
KeywordsKernel row numbers–Quantitative trait loci–Mapping–Maize–Major QTL
[Show abstract][Hide abstract] ABSTRACT: Drought resistance is a complex quantitative trait, involving interactions of many metabolic pathways related to stress-resistant genes. Identification of a standard evaluation assay has been the most pressing problem for selection of drought-resistant genotypes and ultimately for elucidating the internal genetic mechanisms. A field phenotypic investigation was performed on more than 20 morphological traits and grain yield and its components for 201 Chinese common inbred maize (Zea mays L.) lines under water deficit in seven environments. An integrated selection criterion for drought resistance was proposed and used to identify drought-resistant maize genotypes. In it, six traits including grain yield, ear number per plant, kernel number per ear, plant height, anthesis-silking interval and degree of leaf curling were chosen as the most relevant factors related to drought resistance, as determined by statistical analysis. The integrated selection criterion was highly correlated with grain yield under both well-watered and water-stressed regimes, and was also highly correlated with other commonly used selection criteria. Moreover, for 128 (63.7%) inbred lines the evaluation result with this criterion was consistent across more than three environments thus avoiding the effect of genotype environment interaction, though stress level between the different environments largely fluctuated. There were 43 inbred lines evaluated for drought-resistance and most were bred during 1990-2000. The criterion will be useful to identify excellent drought-resistant genotypes in future maize molecular breeding programs.
[Show abstract][Hide abstract] ABSTRACT: Head smut of maize (Zea mays L.), which was caused by Sporisorium reiliana, occurred in most of the maize growing areas of the world. The purpose of this study was to develop SCAR markers for map-based cloning of resistance genes and MAS. Two sets of BC3 progenies, one (BC3Q) derived from the cross Qi319 (resistance) × Huangzao 4 (susceptible), the other (BC3M) from Mo17 (resistance) × Huangzao 4 (susceptible), were generated. Huangzao 4 was the recurrent parent in both progenies. A combination of BSA (bulked segregant analysis) with AFLP (amplified fragment length polymorphism) method was applied to map the genes involving the resistance to S. reiliana, and corresponding resistant and susceptible bulks and their parental lines were used for screening polymorphic AFLP primer pairs. One fragment of P13M61–152 was converted into SCAR (sequence charactered amplified fragment) marker S130. The marker was mapped at chromosome bin 2.09, the interval of a major QTL region previously reported to contribute to S. reiliana resistance. Furthermore, S130 was highly associated with resistance to S. reiliana, and could be useful for marker-assisted selection and facilitate map-based cloning of resistance genes.
Agricultural Sciences in China 08/2009; 8(8-8):910-919. DOI:10.1016/S1671-2927(08)60295-3 · 0.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gln1-4 is one of the important members of glutamine synthetase (GS) gene family. The objectives of this study were to isolate the genomic DNA (gDNA) sequence of Gln1-4, to analyze structure, conserved domains, and natural allelic variations of the gene, and to found a basis for association analysis of the functional sites associated with nitrogen use efficiency in maize (Zea mays L.). PCR walking strategy was applied to isolate the gDNA sequence of Gln1-4 and its flanking sequences. A total of 3724 bp gDNA sequence of Gln1-4 was assembled from the maize inbred line Mo17. The full length of the coding region was 2858 bp, which comprised of 10 exons separated by 9 introns. All the 18 splicing sites were the conserved sequence of GU at the 5′ donor sites and AG at the 3′ acceptor sites. This sequence was submitted to GenBank under the accession number EU369651. Gln1-4 encodes a GS protein with the molecular weight of 39.2 kD, which was composed of 356 amino acids. The isoelectric point was 5.202. Conserved domain searching results showed that the region from exon 2 to exon 6 at amino-terminal was an ammonium-ion-binding domain, and exon 8 to exon 9 at carboxyl terminal consisted of an ATPase activity domain. Compared with Gln1-3, Gln1-4 was highly conserved in DNA sequence, amino acid sequence, gene structure, and conserved domains with a 98.31% identity of amino acid sequence. A total of 318 types of natural DNA variation at the important and target region of Gln1-4 gene were identified among 52 maize inbred lines, of which 90% was single nucleotide polymorphisms (242) and small indels (45). The analysis of the functional sites associated with nitrogen use efficiency of Gln1-4 should focus on the binding and catalyzing domains and the splicing sites.
[Show abstract][Hide abstract] ABSTRACT: A molecular linkage map for the maize hybrid of cross between Ye478 and Dan340 was constructed by using 150 co-dominant SSR markers. The total map length was 1 478.7 cM with an average interval of 10.0 cM. Composite interval mapping was used to identify the plant height (PH) and ear position (EH) QTL at 5 environments based on the phenotypic data of 397 F2:3 families. Then 21 PH and 25 EH relevant QTL were identified. The mean contribution of 12.2% and 14.9% QTL for plant height was identified at the interval of umc2025 - umc1035 on chromosome 1 and umc1822 - bnlg1118 on chromosome 5, respectively. Meanwhile, the mean contribution of 10.2% and 22.8% to ear position were identified at the interval of phi029 - umc1102 on chromosome 3 and phi109188 - bnlg1118 on chromosome 5. The main QTL for PH and EH were both found at the regions of Bin5.05 - 5.07 on chromosome 5. The additive and partial dominant effects were the main genetic basis for plant height and ear position in maize. The effect of population size and environments on QTL mapping were analyzed.
[Show abstract][Hide abstract] ABSTRACT: Sugarcane mosaic virus (SCMV) causes considerable damage to maize (Zea mays L.) in China. Characterization of resistance gene(s) serves as the basis for effective selection in resistance breeding programs. The objective of this study was to identify novel genes conferring resistance to SCMV from maize germplasm in China. A total of 21 BC2F3 populations derived from 8 maize intercross combinations were artificially inoculated with SCMV under field conditions. The numbers of resistant and susceptible plants in the BC2F3 population Ye 478 × Hai 9-21 were consistent with the theoretical 1:3 phenotypic ratio, suggesting that a recessive gene derived from the resistant parent Hai 9-21 was responsible for resistance to SCMV. Bulked segregant analysis (BSA) and simple sequence repeat (SSR) marker analysis were used to verify the recessive resistance gene that was designated scm3. Gene scm3 was located in bin 3.04–3.05, flanked by SSR markers umc1965 and bnlg420 with genetic distances of 45.7 and 6.5 cM, respectively. Four additional linked markers were detected, which were associated with scm3 gene in the order of umc1965–scm3–bnlg420–umc1307–umc2265–bnlg2241–umc2166.
[Show abstract][Hide abstract] ABSTRACT: The development of genomics and bioinformatics offers new tools for comparative gene mapping. In this paper, an integrated QTL map for Sugarcane mosaic virus (SCMV) resistance in maize was constructed by compiling a total of 81 QTL loci available with the Genetic Map IBM2 2005 Neighbors as reference. These 81 QTL loci were scattered on 7 chromosomes of maize, and most of them was clustered on chromosome 3 and 6. By using meta- analysis method, we identified one and two "consensus QTLs" on chromosomes 3 and 6, respectively. These three QTLs cover the genetic distances of 6.44 cM, 6.16 cM and 27.48 cM on the genetic map IBM2 2005 Neighbors, respectively. Four positional candidate resistant genes were identified within the "consensus QTL" on chromosome 3 via comparative genomics strategy. These results suggested that application of the combined meta-analysis within a species with sequence homologous comparison in a related model plant is an efficient approach to identify the major QTL and its candidate gene(s) for the target traits. The results of this study provided useful information for identifying and cloning of the major gene(s) conferring resistance to SCMV in maize.
[Show abstract][Hide abstract] ABSTRACT: Maize (Zea mays L.) breeders have begun selecting for more compact plants for higher density planting in order to increase yield per unit area. Leaf angle and leaf orientation are very important traits affecting maize plant type (compactness). In this study, a genetic linkage map containing 138 simple sequence repeat (SSR) markers was constructed based on a mapping population consisting of 500 F2 individuals from the cross between inbred lines Ye478 and Dan340. This SSR linkage map spans a total of 1 394.9 cM with an average interval of 10.1 cM. Quantitative trait loci (QTL) for leaf angle and leaf orientation were identified in 397 F2:3 families. Six QTL for leaf angle were detected that could explain 41.0% of the phenotypic variation; while, eight QTL were detected for leaf orientation that could explain 60.8% of the phenotypic varia-tion. Single QTL contribution to phenotypic variation ranged from 2.9% to 13.6%. Additive and partial dominance were the main genetic effects for leaf angle and leaf orientation; in addition, nine pairs of locus interactions were detected for the two traits, indicating that epistatic interactions at the two-loci level also play a measurable role in the genetic basis of the two traits.
[Show abstract][Hide abstract] ABSTRACT: Simple sequence repeats (SSRs) and amplified fragment length polymorphisms (AFLPs) have become the most important markers for molecular mapping. Primarily based on restriction fragment length polymorphism (RFLP) markers, extensive linkage maps of maize had been developed. To construct a near-saturated genetic linkage map, an expanded maize genetic linkage map was constructed using a population of 234 F2 individuals derived from a cross of X178 and B73 base on an essential SSR framework map of maize. The level of polymorphisms and genetic properties of SSR and AFLP markers were characterized. A total of 249 markers consisting of 130 SSRs and 119 AFLPs have been landed on 10 chromosomes of maize. The 249-locus map spanned 1 659.3 centi-morgans (cM) and had a mean density of 6.66 cM. This mapping population and related information should connect further research involving analysis of quantitative trait loci, comparative genomics, and heterosis. Moreover, in many studies, AFLPs were analyzed on the basis of the presence or absence of a band on the electrophoresis gels. A new method based on double polymorphic bands of co-dominant scoring of AFLPs was explored according to the similarity of loci amplified from AFLP enzyme combination.