花粉管通道法将淀粉分支酶基因反义表达载体转入玉米自交系的研究

实验主要利用花粉管通道技术将淀粉分支酶基因的反义表达载体转入玉米自交系中,同时探讨了不同导入时间、不同DNA浓度、不同导入量等对其转化率的影响,并从中得出花粉管通道法的最佳转化条件。同时将转化的玉米植株进行PCR检测,初步证明外源目的基因已整合到玉米基因组中,并得到了转化植株的种子。

Combining Ability and Correlation of Ear Characteristics of Twenty Maize Inbred Lines

The combining ability and correlation of eight ear characteristics in 99 maize hybrids generated by crossing nine female parents with 11 male parents were analyzed by incomplete diallel cross （NC II ） design. The results showed that the line F6 had the highest general combining ability （GCA） for yield, followed by F7, M3, M4 and M8. All of the five lines have great potential in maize breeding. The cross combination M3xF10 had the highest specific combining ability （SCA） for yield, showing strong heterosis. Heritability analysis of ear characteristics showed that GCA variance was higher than SCA variance in ear diameter, number of rows per ear and seed rate, and they were mainly controlled by the additive gene effect, indicating that that the selections for these traits are effective at early generations. The other three traits had lower SCA, for which the selections should be carried out at late generations. The correlation analysis revealed that ear length, number of grains per row, ear diameter, number of rows per ear, 100-seed weight and seed rate had extremely significant positive correlations with grain yield per plant. Among them, number of grains per row had the most significant effect on yield per plant. Barren tip length had a significant negative correlation with grain yield per plant. Therefore, we concluded that the combinations with more grains per row and shorter barren tip should be selected to achieve high yield of maize.

Analysis on Combining Ability and Genetic Parameters of Main Agronomic Characters of 22 Maize Inbred Lines

The general combining ability（GCA）, special combining ability（SCA） and genetic parameter of ten characters of 22 maize inbred lines including plant height and ear height were analyzed using 10×12 through incomplete diallel cross（NC Ⅱ）.The results showed that：（1） Among the 22 maize inbred lines, the yield GCAs of11 HN 097, 11 HN 099, 11 HN 105 and 11 HN 110 were high, which were elite inbred lines to collocate hybridized combinations with strong heterosis. The yield of11 HN110 × 11 HN097, 11 HN110 × 11 HN105, 11 HN112 × 11 HN 097 and 11 HN 106 × 11 HN 104 were in the first four place. The yielding abilities, adaptabilities and yielding stabilities of the four combinations can be further identified by experiment. The heredities of the ten characters were mainly controlled by additive gene effect whereas the influence of non-addictive gene effect was small. The narrow heritabilities of plant height, ear height, ear rows, ear length, kernels per row,100-grain weight and seed-producing percentage were more than 50%. The variances were mainly caused by heredity and early-generation selection should be conducted. The narrow heritabilities of ear diameter, bare tip length and yield was low, which should not be selected in early-generation.

Combining Ability Analysis of Panicle Traits in Six CIMMYT Maize Inbred Lines

In this study, six CIMMYT maize inbred lines and five representative do- mestic maize inbred lines were used as parental lines. By using incomplete diallel cross design, 30 hybrid combinations were developed to analyze the general com- bining ability （GCA）, specific combining ability （SCA） and total combining ability （TCA） of seven panicle traits in six CIMMYT maize inbred lines. The results showed that CIMBL98 and GEMS13 were excellent inbred lines with good compre- hensive performance; CIMBL98 × 340 and GEMS13×Chang 7-2 were superior combinations.

Selection of Maize Inbred Lines with High Regeneration and Susceptibility to Agrobacterium tumifacien

Ten-maize inbred lines of maize （Zea mays L.） with high-induction rate and proliferation ability of embryonic calli were selected from 70-maize inbred lines by immature embryo culturing. Some of the embryonic calli were transferred onto regeneration medium to examine the ability of regeneration, some were transformed via Agrobacterium tumifaciens C58 carrying intron-β-glucuronidase （gus） gene, and GV3301 carrying the green fluorescent protein （gfp） gene to study the susceptibility of different genotypes in maize to A. tumifaciens. All embryonic calli initiated from 10-maize inbred lines were able to regenerate into plantlets, and the regeneration frequencies of inbred lines 6010, 6038, 6015, 6051, and 6060 were 61.11%, 31.94%, 45%, 33.33%, and 56.94%, respectively, which were higher than that of other lines. Analysis of variance indicated that the susceptibility of the various genotypes in maize to A. tumifacien C58 showed a significant difference among each other, and the inbred lines 6010, 6015, 6051, 6050, 6058, 6060, 6069, 6077 were susceptible to A. tumifacien C58, of which frequency of gus expression were over 70%. Expression of GFP was observed in six-inbred lines （6050, 6015, 6051, 6058, 6069, 6077）. The inbred lines 6051, 6010, 6015, 6060, and 6050 had the high regeneration and the susceptibility to A. tumifaciens C58; and the inbred lines 6051, 6015, and 6060 had the high regeneration and the susceptibility to Agrobacterium tumifaciens GV3301.

Enhancing Maize Grain Yield in Acid Soils of Western Kenya Using Aluminium Tolerant Germplasm

Maize （Zea mays L.） is one of the world＇s most important cereals and is a staple food for many people in developing countries. However, in acid soils （pH 〈 5.5）, its productivity is limited by aluminium （AI） toxicity, besides other factors. The objectives of this study were to： develop AI tolerant maize inbred lines for a maize breeding program in Kenya, develop single cross hybrids （SCHs） from some of the tolerant inbred lines and determine AI tolerance levels of the SCHs. One hundred and seventy five inbreds and 49 SCHs were developed and screened in nutrient culture containing 0 or 222μM using Relative Net Root Growth （RNRG）, hematoxylin staining （HS） and under AI saturated field conditions （44%-45.6%） at Sega and Chepkoilel. Seedling root growth was inhibited in 95% of the inbreds. F hybrids obtained from inbreds varying in A1 tolerance, exhibited tolerance equal to or greater than that of the more tolerant parent indicating a positive transgressive inheritance to AI toxicity. Fifty eight percent of the F SCHs were heterotic for tolerance to AI toxicity. AI tolerance estimated by RNRG was well correlated to that of HS （r2 = 0.88, P 〈 0.005） but minimally correlated with the field estimates （r2 = 0.24-0.35）, implying that RNRG can predict field selection under AI toxic soils by between 24% and 35%. Plant breeders should therefore employ both approaches in selecting cultivars under AI stress. This study has developed and identified A1 tolerant inbreds and SCHs for use in the acid soils of Kenya and similar regions.

Analysis on Breeding Potential of 17 Maize Inbred Lines from Land Races

[Objective] The primary objective of this study was to estimate combining ability and genetic parameters of 17 new inbred lines.[Method] By using 11 commonly used maize inbred lines from Southwest China as testers and incomplete diallel cross design,combining ability and heterosis of 17 new inbred lines bred from the land races in Sichuan Basin and its surrounding areas were analyzed.In addition,the genetic parameters and heterotic groups were also investigated based on combining ability.[Result] P1-1,P1-16 and P1-14 with the better comprehensive characters can be directly used in maize breeding program.The SCA of P1-10×P2-4 was high in most traits.It is more possible to obtain high-yield hybrid combinations by the pattern Sipingtou × Lancaster.GCA variance was bigger than SCA variance in four traits such as rows per ear,grains per row,which were affected by the environments slightly and should be selected at early generations;while SCA variance was bigger than GCA variance in five traits such as 100-grain weight and plant weight,which were significantly influenced by environment and thus should be selected in later generations.[Conclusion] The paper will provide theoretical basis for further improvement of local maize varieties.

Molecular Cloning and Expression Analysis of zm NAC Transcription Factor Gene

In order to study NAC transcription factor gene in maize(Zea mays), a completed c NAC encoding the NAC-like gene homologue named as Zm NAC was cloned from the maize inbred line Zheng 58 using a pair of specific primers, which were designed to cover the full coding region according to the reported NAC gene family. The length of the sequences was 953 bp.The deduced amino acid sequences analysis showed that the sequence contained the complete coding region of a typical NAC gene, including a complete open reading frame which was 939 bp. The study analyzed the expression patterns of NAC transcript gene induced in various PEG(polyethylene glycol) simulated drought condition. Real-time PCR indicated that maize NAC gene can be induced in various PEG to abiotic stress responses, it could express constitutively to adopt the drought condition in short time, and the higher drought, the more early expression, which indicated that NAC transcript gene could be involved in the regulation of the defense response.

Variability of Phytic Acid and Inorganic Phosphorus Contents in Seeds of Tropical Maize （Zea mays L.）

The correlation coefficients and scattering were studied in Ki and new inbred lines for phytic acid （PA） and inorganic phosphorus content （InP） content in seeds of tropical maize （Zea mays L.）. The understanding of the variability in PA and InP characters would be useful in a breeding program. A total of 16 Ki and 25 new inbred lines of tropical maize were planted in Completely Randomized Design （CRD） during late rainy season, 2007 to early rainy season, 2009 at Inseechandrastitya Institute for Crops Research and Development, Thailand. The result showed low correlation with no statistical significant between PA and InP contents in corn seeds performed either in different sources of inbred lines or years. For PA content, most of inbred lines were skewed toward high PA （〉 900 mg/100 g） both in Ki and new inbred lines in every year. The lowest PA value found in Ki inbred lines both in two years were Ki10, Ki15, Ki20, and Ki52.30A10-S11-43-1-3 was the lowest PA inbred lines observing in two years in new germplasm.

The Genetic Variances for the Phytic Acid and Inorganic Phosphorus Contents of Elite Inbred Lines in Tropical Maize

The study aimed to determine the genetic variances of phytic acid （myo-inositol 1,2,3,4,5,6 hexakis-dihydrogen phosphate） （PA） and inorganic phosphorus contents （InP） in grains of tropical maize （Zea mays L.）. The understanding of genetic variances in PA and InP in tropical maize would be useful for breeding management in tropical region. A total of 16 Ki inbred lines and 26 new inbred lines of tropical maize were planted in Completely Randomized Design （CRD） on the dry season 2008 at lnseechandrastitya Institute for Crops Research and Development, Thailand. The results showed that genotypic differences were highly significant （P 〈 0.01） for InP in both sources of germplasm, but genotype effect only was found significant in new inbred lines for PA content. The values for broad sense heritability （h2b） was generally lower on PA in maize grains compared with InP both in Ki and new inbred lines [h^2b of PA： 2.42 （Ki）, 14.18 （commercial hybrid extracted）; h^2b of InP： 32 （Ki） and 29.53 （commercial hybrid extracted）].

Media Appraisal for Somatic Embryogenesis of Elite Inbred Lines of Maize

Several protocols have been published for somatic embryogenesis in maize. It is essential to compare different protocols on selected germplasm at initial stages of tissue culture to identify a protocol that would yield optimum results. The ultimate goal is to use in vitro system for selecting and generating stress tolerant maize germplasm. Immature embryos of the elite inbred lines of maize （87014 ×Z28-11 and POP43SRS5-57） were cultured on three different semi-solid media （0.5% agar） and the effectiveness of the media for somatic embryogenesis assessed over a period two weeks of sub-culturing. A significant difference was observed among the media in proportion of potentially embryogenic calli and callus cluster size at 1 and 2 weeks after culturing. N6 medium supplemented with casaminoacid （100 mg/L）, 2, 4-dichlorophenoxy acetic acid （1 mg/L）, L-proline （25 mM） and sucrose （2%）, and Murashige and Skoog （MS） medium supplemented with 2, 4-D （2 mg/L） and sucrose （3%） gave higher proportion of potentially embryogenic calli and callus size than MS medium supplemented with casaminoacids （100 mg/L）, 2, 4-D （2 mg/L）, abscissic acid （3.3μM）, and silver nitrate （195 μM） and sucrose （3%）. The difference between genotypes is not significant

Dicamba Growth Regulator Promotes Genotype Independent Somatic Embryogenesis from Immature Zygotic Embryos of Tropical Maize Inbred Lines

Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotypes indicates that callus induction and genetic transformation is dependent on the genotype. This phenomenon is an impediment in the fundamental process of improving tropical maize germplasm especially through genetic engineering. Here, five tropical maize （Zea mays L.） genotypes, CML 216, CML 144, A 04, E 04 and TL 21, were evaluated for callus induction on MS medium supplemented with the growth regulator dicamba. Embryogenic and non embryogenic callus induction was independent ofgenotype when young immature embryos, 12 days after pollination （DAP） were used for tissue culture in combination with dicamba. The optimal concentration of dicamba for induction ofembryogenic callus in all the genotypes was 3 mg/L, which was also the concentration at which non embryogenic callus formation was lowest. The frequency of embryogenic callus induction ranged from 35% to 79% among the five genotypes and somatic embryos regenerated R0 shoots that produced normal R1 progenies. This regeneration method is expected to facilitate the development of a more efficient genotype independent Agrobacterium- mediated transformation system for tropical inbred lines.

Genetic Analysis of Segregation Distortion of Molecular Markers in Maize RIL Population

A RIL population was used in this study, which was derived from a cross between a temperate maize germplasm inbred line B31-1 and a tropical maize germplasm inbred lines Huangzao 4. A genetic linkage map was constructed comprising of 153 polymorphic markers. Among the 153 polymorphic markers, 82 markers showed the significantly segregation distortion（P〈0.05）, favoring either the marker alleles of female parent 1331-1（62.50%） or male parent Huangzao 4（37.50%）. Segregation distortion marker distribution along the present molecular maps of maize was far from uniform, with clusters of tightly linked loci and single marker. Nine segregation distortion regions were detected on 10 chromosomes, indicating that possible causes for segregation deviation of molecular markers are genetic selection.

Seed priming with chitosan improves maize germination and seedling growth in relation to physiological changes under low temperature stress

Low temperature stress during germination and early seedling growth is an important constraint of global production of maize. The effects of seed priming with 0.25%, 0.50%, and 0.75% （w/v） chitosan solutions at 15 ℃ on the growth and physiological changes were investigated using two maize （Zea rnays L.） inbred lines, HuangC （chilling-tolerant） and Mo17 （chilling-sensitive）. While seed priming with chitosan had no significant effect on germination percentage under low temperature stress, it enhanced germination index, reduced the mean germination time （MGT）, and increased shoot height, root length, and shoot and root dry weights in both maize lines. The decline of malondialdehyde （MDA） content and relative permeability of the plasma membrane and the increase of the concentrations of soluble sugars and proline, peroxidase （POD） activity, and catalase （CAT） activity were detected both in the chilling-sensitive and chilling-tolerant maize seedlings after priming with the three concentrations of chitosan. HuangC was less sensitive to responding to different concentrations of chitosan. Priming with 0.50% chitosan for about 60-64 h seemed to have the best effects. Thus, it suggests that seed priming with chitosan may improve the speed of germination of maize seed and benefit for seedling growth under low temperature stress.