Chloroplast DNA polymorphism in fertile and male-sterile cytoplasms of sorghum (Sorghum bicolor (L.) Moench)

Summary Restriction endonuclease patterns of chloroplast DNA (cpDNA) were consistently distinguishable between fertile and male-sterile cytoplasms of sorghum [Sorghum bicolor (L.) Moench], whereas no differences in restriction patterns of cpDNA among male-sterile (A₁) lines, including six isocytoplasmic strains, were revealed in this study. It is suggested that chloroplast DNA may contribute to the male sterility of A₁ lines used currently in hybrid sorghum production.This research was supported by a research grant from Kansas Grain Sorghum Commission, Kansas Board of Agriculture. Contribution 90-293-J from the Kansas Agricultural Experiment Station     

Variability and correlation of iron-deficiency symptoms in a sorghum population evaluated in the field and growth chamber

Summary One hundred S₁ families from a random-mating sorghum [Sorghum bicolor (L.) Moench] population (NP21R) were rated visually for differences in iron-deficiency chlorosis in the field and in a growth chamber. Heritabilities on a family-mean basis were estimated for the first (0.63±0.15), maximum (0.79±0.15), and average chlorosis rating (0.84±0.15) recorded over S₁ families in the field. Heritability on an individual plant basis was estimated for the average chlorosis ratings in the growth chamber (0.65±0.16). Phenotypic and genotypic correlations were large and negative between field chlorosis ratings and yield or yield-related traits, which indicated that the severity of chlorosis was an important factor in determining S₁ family agronomic performance. Correlations between chlorosis traits over all S₁ families in the growth chamber and field generally were small and nonsignificant.     

AtNHX1基因对荞麦的遗传转化及抗盐再生植株的获得

通过农杆菌介导法将拟南芥液泡膜Na⁺/H⁺反向转运蛋白基因AtNHX1转入荞麦中,在2.0mg/L 6-BA、0.1mg/L IAA、1mg/L KT、50mg/L卡那霉素和500mg/L头孢霉素的MS培养基上进行选择培养,从来源于864块外植体的36块抗性愈伤组织中共获得426棵再生植株（转化频率为4.17%）。经PCR、Southern印迹分析、RT-PCR和Northern检测,初步证实AtNHX1基因已整合至荞麦基因组中。用200mmol/L的盐水对转基因植株和对照植株进行胁迫处理6周,转基因植株能够生存,而对照植株死亡。用不同浓度的NaCl溶液处理转基因植株和对照植株,发现Na⁺及脯氨酸含量在转基因植株中的积累水平显著高于对照植株,而K⁺的含量在转基因植株中的积累水平低于对照植株。次生代谢产物黄酮类化合物芦丁在转基因植株根、茎和叶片中的含量也比对照植株明显要高。这些结果表明利用基因工程手段提高作物的耐盐性是可行的。     

Pseudogamous Apomixis in Maize and Sorghum in Diploid-Tetraploid Crosses

Apomictic seed development is a complex process including formation of unreduced embryo sac, parthenogenetic embryo development from the egg cell, and endosperm formation either autonomously, or due to fertilization of polar nuclei by the sperm (under pseudogamous form of apomixis). In the latter case, an obstacle to the normal endosperm development is disturbance of maternal (m) -to-paternal (p) genomic ratio 2m: 1p that occurs in the cases of pollination of unreduced embryo sac with haploid sperms. Usage of tetraploid pollinators can overcome this problem because in such crosses maternal-to-paternal genomic ratio is 4m: 2p that provides formation of kernels with plump endosperm. Using tetraploid lines as pollen parents we observed formation of plump kernels on the ears and panicles of diploid maize and sorghum accessions. These kernels had hybrid endosperm and diploid maternaltype embryo or hybrid embryo with different ploidy level (2n, 3n, 4n). The frequencies of plump kernels on the ear ranged from 0.2-0.3% to 5.7-6.2% counting from the number of ovaries. Maternal-type plants were found in two maize lines, their frequency varying from 10.7 to 37.5% of the progeny plants. In CMS-lines of sorghum pollinated with tetraploid sorghum accessions, the frequency of plump kernels ranged from 0.6 to 14.0% counting from the number of ovaries; the frequency of maternal-type plants varied from 33.0 up to 96.1%. The hybrid nature of endosperm of the kernels that gave rise to maternal-type plants has been proved by marker gene expression and by SDS-electrophoresis of endosperm proteins. These data testify to variable modes of seed formation under diploid × tetraploid crosses in maize and sorghum both by amphi- and by apomixis. Therefore, usage of tetraploid pollinators might be a promising approach for isolation of apomixis in maize and sorghum accessions.     

Restriction endonuclease analysis of mitochondrial DNA from sorghum with fertile and male-sterile cytoplasms

Summary Mitochondrial DNA from four paired (fertile and male-sterile) lines and six isocytoplasmic strains of sorghum (Sorghum bicolor (L.) Moench) were fragmented by endonucleases and their electrophoretic patterns were examined. Cytoplasmic male sterile lines differed from their male-fertile counterparts consistently. Among the isocytoplasmic strains, KS 36A (S. verticilli-florum cytoplasm), KS 38A (S. conspicum cytoplasm), and KS 39A (S. niloticum cytoplasm) showed minor differences from the other strains. Results suggest that restriction endonuclease patterns are useful in detecting differences in mitochondrial genomes.This study was supported by a research grant from Kansas Grain Sorghum Commission, Kansas Board of Agriculture. Contribution 89-28-J from the Kansas Agricultural Experiment Station.     

Identification of galloylated propelargonidins and procyanidins in buckwheat grain and quantification of rutin and flavanols from homostylous hybrids originating from F. esculentumxF. homotropicum

The flavonoid rich grain of buckwheat (Fagopyrum esculentum Moench, Fam. Polygonaceae) is of high nutritional value. With the aim to improve its agronomic productivity, cultivars were crossed with the wild species F. homotropicum which, however, differs in its flavonoid content. The intention of this work was to determine the flavonoid composition in developed interspecific hybrids and to elucidate the proanthocyanidin structures. Seven compounds were purified from methanol extracts of buckwheat (Fagopyrum esculentum Moench) grains by Sephadex LH-20 column chromatography. Beside the procyanidin epicatechin-[4-8]-epicatechin-3-O-(3,4)-dimethylgallate the following propelargonidins were identified: epiafzelechin-[4-6]-epicatechin, epiafzelechin-[4-8]-epiafzelechin-[4-8]-epicatechin, epiafzelechin-[4-8]-epicatechin-3-O-(3,4-dimethyl)-gallate, epiafzelechin-[4-8]-epiafzelechin-[4-8]-epicatechin-3-O-(3,4-dimethyl)-gallate, epiafzelechin-[4-8]-epicatechin-3-O-4-methyl-gallate and epiafzelechin-[4-8]-epicatechin-p-OH-benzoate on the basis of HPLC and LC-MS/MS.     

甜荞FaesAP2基因的克隆与表达分析

本研究采用同源克隆和RACE技术,从甜荞（Fagopyrum esculentum Moench.）品种'西农9976'中分离出调控花器官发育的FaesAP2基因,该基因序列全长1668 bp,包含1个长为1374 bp的完整开放阅读框,共编码457个氨基酸。序列比对以及系统发育分析结果发现,FaesAP2蛋白拥有2个高度保守的AP2（APETALA2）结构域,在第1个AP2结构域前端有1段由10个氨基酸残基组成的高度保守的核定位信号区;系统发育分析显示其与拟南芥（Arabidopsis thaliana（L.） Heynh.） AP2转录因子的亲缘关系较近。基因表达模式分析表明,该基因在甜荞pin型和thrum型花的雄蕊和雌蕊中有明显的表达,但在幼叶和花被片中不表达,且其表达量在2种类型花不同发育时期呈现明显的变化,均在花药迅速膨大期达到最高值,因此推测该基因在甜荞花发育过程中可能参与了花器官发育的调控。     

Effects of Al on nitrogen (NH 4 + and NO 3 − ) uptake,nitrate reductase activity and proton release in two sorghum cultivars differing in Al tolerance

After growth for 17 to 36 days on nutrient solutions with NH₄NO₃ as nitrogen source (pH 4.2) dry matter of sorghum genotype SC0283 was much less affected by Al (1.5 and 3.0 ppm) than that of genotype NB9040. In the absence of Al both cultivars released protons into the nutrient solution as a result of an excess of cationic nutrients taken up. When Al was present, this proton efflux per unit dry weight increased drastically, especially with the sensitive genotype NB9040. Chemical analysis of plant material and continuous analyses of NO ₃ ⁻ and NH ₄ ⁺ in the nutrient solution indicated, that the Al-induced shift in H⁺-balance of both genotypes could almost completely be attributed to a decreased NO ₃ ⁻ /NH ₄ ⁺ uptake ratio. In vivo nitrate reductase activity (NRA) was reduced in the shoot of NB9040 and to a lesser degree in SC0283. Al-induced decrease in NRA was accompanied by similar percentual decreases in NO ₃ ⁻ tissue concentrations. Therefore this decrease is interpreted as being indirect,i.e., the consequence of the reduced NO ₃ ⁻ uptake of the plants. A direct repression of NRA by Al seems also unlikely because nitrate reductase activity of the roots (where cellular Al-concentrations should be higher than in shoots) was not affected in Al-treated plants of either genotype.     

Screening for drought tolerance in Sorghum using cell culture

Summary Callus growth from 10 cultivars ofSorghum bicolor (L.) Moench was measured with increasing levels of polyethylene glycol (PEG) as an osmoticum in the medium to determine whether differences among these cultivars at the cellular level in response to osmotic stress existed. These cellular ratings were compared to field ratings from the 10 tolerant-to-susceptible cultivars when grown under drought conditions to determine whether cellular ratings corresponded to differences in drought tolerance at the plant level. Callus cultures were grown on Murashige and Skoog inorganic salt formulation plus vitamins, 2,4-dichlorophenoxyacetic acid (2,4-D), kinetin and sucrose, supplemented with 0 to 25% (wt/vol) PEG corresponding to −0.2 to −1.62 MPa osmotic potential. Results suggest that PEG-induced osmotic stress on callus cultures can be used to screen sorghum cultivars for potential early field (preflowering) drought tolerance. This implies that at least a component of the early field drought tolerance in sorghum may have a cellular basis. This study was supported by U.S. Agency for International Development Grant AID/DSAN/XII/G-0149, and USDA Competitive Grants Program.     

荞麦种子萌发期多种抗氧化酶活性的研究

通过研究荞麦种子萌发期(0～7 d)超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化物酶(ASP)四种抗氧化酶的酶活性变化,以及对自由基等的清除效果,分析荞麦种子内在抗氧化酶系统在萌发期对细胞膜结构的修复及保护作用。实验结果表明:荞麦种子在萌发期产生的活性氧、自由基等对四种抗氧化酶均有激活效应,其中超氧化物歧化酶(SOD)活性最先上升,其他三种酶随其后被激活,四种酶的氧化反应存在一定关联性和协同作用。苦荞的抗氧化酶活性高于甜荞。