利用大刍草渗入系群体定位玉米株高和穗位高QTL

利用玉米自交系W22与大刍草杂交衍生得到的包含866个家系的渗入系群体,结合均匀覆盖玉米全基因组的19 838个SNP分子标记,采用R/qtl的多QTL模型对玉米株高和穗位高进行高精度的QTL定位分析。结果表明:玉米株高和穗位高存在广泛的遗传变异,属于典型的数量性状,由微效多基因控制;共检测到4个控制株高的QTL,分别位于第1、5和8染色体上,单个株高QTL表型贡献率变幅为2.33%～4.85%,加性效应的变幅为2.33～6.01cm;共检测到10个控制穗位高的QTL,分别位于第1、2、3、5、6、7和8染色体上,单个穗位高QTL表型贡献率的变幅为1.77%～6.15%,加性效应的变幅为1.75～6.25 cm。     

大刍草苗期转录组RNA-Seq数据的de novo拼接

采用solexa测序技术,对大刍草苗期全株各组织转录组进行了RNA-Seq测序、de novo拼接和信息比对研究。结果表明:转录组测序共得到了46.4 GB的原始数据,归并整理后获得长76 bp的序列有175 101 250条,经质量控制和de novo拼接后,共获得了58 147条大刍草转录本,其平均长度为1 335 bp。比对分析发现其中94.3%的转录本和玉米B73自交系的cDNA序列有较好的匹配,与水稻匹配的有84.1%,高粱84.6%,短柄草83.9%,共56 036条转录本。     

AFLP–SSR maps of maize × teosinte and maize × maize: comparison of map length and segregation distortion

Two genetic linkage maps of Zea mays were constructed: one population comprised 94 F₂ individuals of a dent ‘B64’ × teosinte (Z. mays ssp. huehuetenangensis) cross while the second consisted of 94 F₂ individuals of a ‘B64’ × Caribbean flint ‘Na4’ cross. The level of polymorphism was higher in the ‘B64’ × teosinte combination than the ‘B64’ × ‘Na4’ combination. In the ‘B64’ × teosinte cross, a total of 338 amplified fragment length polymorphism (AFLP) and 75 simple sequence repeat (SSR) markers were mapped to 10 chromosomes, which covered 1402.4 cM. In the ‘B64’ × ‘Na4’ cross, a total of 340 AFLP and 97 SSR markers were mapped to 10 chromosomes, covering 1662.8 cM. Segregation distortion regions were found on chromosomes 4, 5 and 8 in the ‘B64’ × teosinte cross and on chromosome 9 in the ‘B64’ × ‘Na4’ cross. Comparison of the two maps revealed that the maize × teosinte map was 11.5% shorter than the maize × maize map. The maps generated in this study may be useful to identify genes controlling flooding tolerance.     

Identification of QTL controlling adventitious root formation during flooding conditions in teosinte (Zea mays ssp. huehuetenangensis) seedlings

Adventitious root formation (ARF) at the soil surface is one of the most important adaptations to soil flooding or waterlogging. Quantitative trait loci (QTL) controlling ARF under flooding condition were identified in a 94 F₂ individual population by crossing maize (Zea mays L., B64) × teosinte (Z. mays ssp. huehuetenangensis). A base-map was constructed using 66 SSR and 42 AFLP markers, covering 1,378 cM throughout all ten maize chromosomes. The ARF capacity for seedlings was determined by evaluating the degree of root formation at the soil surface following flooding for 2 weeks. ARF showed continuous variation in the F₂ population. Interval mapping and composite interval mapping analyses revealed that the QTL for ARF was located on chromosome 8 (bin 8.05). Utilising a selective genotyping strategy with an additional 186 F₂ population derived from the same cross combination and 32 AFLP primer combinations, regions on chromosomes 4 (bin 4.07) and 8 (bin 8.03) were found to be associated with ARF. Z. mays ssp. huehuetenangensis contributed all of the QTL detected in this study. Results of the study suggest a potential for transferring waterlogging tolerance to maize from Z. mays ssp. huehuetenangensis.     

饲料作物高产栽培技术研究 Ⅳ.大刍草的留茬高度与死株现象的研究

大刍草在连续刈割的条件下,会出现部分的死株现象,严重影响鲜草产量的提高和稳定.经过1987、1988两年试验证明:要获取每亩累计鲜草7500kg 以上产量指标,必须控制第一次刈割时的起点留茬高度不应低于13.2cm;延续刈割时,留茬高度必须递增。     

Variations in physiological,biochemical, and structural traits of photosynthesis and resource use efficiency in maize and teosintes (NADP-ME-type C4)

C₄ plants show higher photosynthetic capacity and resource use efficiency than C₃ plants. However, the genetic variations of these traits and their regulatory factors in C₄ plants still remain to be resolved. We investigated physiological, biochemical, and structural traits involved in photosynthesis and photosynthetic water and nitrogen use efficiencies (PWUE and PNUE) in 22 maize lines and four teosinte lines from various regions of the world. Net photosynthetic rate (P_N) ranged from 32.1 to 46.5 μmol m^?2 s^?1. P_N was positively correlated with stomatal conductance, transpiration rate, and chlorophyll, nitrogen and soluble protein contents of leaves, but not with specific leaf weight. P_N was positively correlated with the activities of ribulose-1,5-bisphosphate carboxylase/oxygenase and the C₄-acid decarboxylases, NADP-malic enzyme and phosphoenolpyruvate carboxykinase, but not with the activity of phosphoenolpyruvate carboxylase. Leaf structural traits (stomatal parameters, leaf thickness, and interveinal distance) were not correlated with P_N. These data suggest that physiological and biochemical traits are involved in the genetic variation of P_N, but structural traits are not directly involved. PWUE is in the lower class of values reported for C₄ plants, whereas PNUE is in the highest class of values reported for C₄ plants. PNUE was negatively correlated with leaf nitrogen content but not significantly correlated with P_N. PWUE was not correlated with δ¹³C values of leaves, indicating difficulty in using δ¹³C values as an indicator of PWUE of maize. In general, teosinte lines showed lower P_N but higher PWUE than maize lines.     

Effects of high temperatures on mature pollen grains in wild and cultivated maize accessions

Summary The effects of high temperature on mature pollen of various maize lines were investigated. Genotypic differences in pollen reaction to high temperature were revealed. Pollen grains resistant to high temperature (35°C, 26°C) were characterized by higher germination capacity and better ability to develop normal pollen tubes. The studies are of interest to evaluate reproductive system tolerance and conduct gamete selection at the mature pollen grain stage in maize.     

The rhizospheric microbiome becomes more diverse with maize domestication and genetic improvement

Domestication and genetic improvement of maize improve yield and stress tolerance due to changes in morphological and physiological properties, which likely alter rhizosphere microbial diversity. Understanding how the evolution of maize germplasm impacts its rhizobacterial traits during the growth stage is important for optimizing plant-microbe associations and obtaining yield gain in domesticated germplasms. In this study, a total of nine accessions representing domestication and subsequent genetic improvement were selected. We then sequenced the plant DNA and rhizobacterial DNA of teosinte, landraces and inbred lines at the seedling, flowering and maturity stages in a field trial. Moreover, the soil chemical properties were determined at the respective stages to explore the associations of soil characteristics with bacterial community structures. The results showed that domestication and genetic improvement increased the rhizobacterial diversity and substantially altered the rhizobacterial community composition. The core microbiome in the rhizosphere differed among germplasm groups. The co-occurrence network analysis demonstrated that the modularity in the bacterial network of the inbred lines was greater than those of teosinte and the landraces. In conclusion, the increased diversity of the rhizobacterial community with domestication and genetic improvement may improve maize resilience to biotic stresses and soil nutrient availability to plants.