化感水稻内生真菌的分离鉴定及其发酵产物的生物学效应研究

以化感水稻品种‘PI312777’‘6173’和‘6180’为研究对象,从水稻根、茎和叶中分离获得70株内生真菌,采用形态学观察和rDNA-ITS区序列分析,对内生真菌进行分类鉴定。进一步以化感水稻‘PI312777’分离得到的粘红酵母和塔宾曲霉为试验菌株,通过不同稀释倍数的真菌发酵液对非化感水稻进行MS半固体培养基育苗试验,研究化感水稻内生真菌发酵产物对非化感水稻萌发率、株高等形态指标及苯丙氨酸解氨酶（PAL）、过氧化氢酶（CAT）和过氧化物酶（POD）活性的影响。结果表明,从供试化感水稻品种中共分离得到17种内生真菌,经rDNA-ITS系统发育树分析鉴定为10个属,这些内生真菌主要分布在曲霉属（Aspergillus）（29.63%）、青霉属（Penicillium）（16.67%）和镰刀菌属（Fusarium）（12.96%）。不同稀释浓度塔宾曲霉发酵液对水稻幼苗生长均有促生作用,其中50倍稀释浓度处理可显著提高水稻幼苗的株高、根长及POD酶活性。粘红酵母菌发酵液5倍稀释浓度可显著提高水稻幼苗的PAL酶活性并对水稻幼苗有促生作用。稗稻共生条件下,塔宾曲霉和粘红酵母发酵稀释液对水稻均有促生效应。本研究可为化感水稻内生真菌进一步应用于水稻生产实践提供有益指导。     

大气CO2浓度升高条件下移栽水稻与不同出苗时间稗草竞争的响应差异

通过田间试验,研究了FACE（开放式空气CO2浓度升高）条件下,移栽稻田水稻（Oryza sativa）与不同发生时期稗草（Echinochloa crusgalli）生长和竞争的响应差异。结果显示,FACE条件下水稻与稗草比例为1∶1时,水稻分蘖、生物量和产量均增加,而稗草则减少。水稻与移栽稻田本田萌生稗草的生物量比率增加181.7%、产量比率增加259.7%、茎蘖比率增加24.2%、有效分蘖比率增加186.3%,水稻竞争优势增加,而移栽稻田本田萌生稗草竞争能力下降。水稻与秧田萌生稗草的竞争关系变化趋势在营养生长期与上述情况相同,但进入生殖生长后水稻竞争优势不再显著,FACE条件下与秧田萌生稗草竞争的水稻最终生物量和产量分别增加22.7%和8.2%,但秧田萌生稗草的最终生物量和产量也增加了11.9%和9.5%。水稻与秧田萌生稗草的生物量比率、茎蘖比率和产量比率增加均不显著。 可见,田间大气CO2浓度升高条件下水稻与稗草的竞争关系发生的变化与稗草发生时期有重要关系。     

根系内生细菌与玉米抗纹枯病关系研究

通过对辽宁省14个玉米主栽品种抗性和内生细菌相互关系的研究,明确了苗期不同品种间内生细菌总量差异显著性达到α=0．05水平,而抽丝期品种间差异不显著,苗期与成株期的互作差异亦不显著;品种苗期与成株期内生细菌种群总量不相关;不同品种苗期和成株期纹枯病抗性均存在显著差异（α=0．01）;玉米纹枯病品种抗性与内生细菌总量不相关,而与拮抗内生细菌百分率呈显著正相关。     

水稻种质对稗草和莴苣的化感效应研究

用改进的叶浸提法和田间共生鉴定法,比较分析了从124份不同来源水稻种质中初步筛选的27份化感种质对稗草和莴苣的化感抑制效果。结果表明,叶浸提液对莴苣的抑制效果明显大于稗草;对稗草和莴苣根长的抑制效果大于苗高和发芽势;叶浸提液法与田间共生法对稗草的抑制效果呈显著的正相关,两种方法的鉴定结果有较高的一致性。叶浸提液对稗草发芽势的抑制指数与田间共生对稗草苗干重的抑制指数及其综合抑制指数呈极显著的正相关,认为稗草种子发芽势可作为测试水稻种质化感效应的重要指标。田间水稻苗高与叶浸提液对稗草根长的抑制指数及其综合抑制指数和田间共生对稗草苗高和苗干重的抑制指数及其综合抑制指数呈极显著的正相关,水稻苗高较高的种质较苗矮的种质表现出较强的化感效应。珍珠42、沙粘1、六月早、青团2号、红脚粘2和地谷的化感效应突出,对稗草的平均综合抑制指数分别为0.56、0.47、0.45、0.45、0.41和0.39,可作为强化感种质提供应用。     

广西香蕉根系内生真菌的群落组成与多样性

本研究对广西香蕉主产区的香蕉根系样本进行内生真菌分离,采用形态学与ITS序列分析相结合的方法进行菌株鉴定,开展其物种组成与多样性分析,对了解广西香蕉与其根部内生真菌间的关系以及探索其内生真菌功能具有重要意义。从168个香蕉根段中共分离获得352株内生真菌,分别归属于5纲17目34科43属62个分类单元,不同分类单元的代表菌株中,有41株菌株能够产生分生孢子(66.13%)。其中,优势纲为粪壳菌纲(Sordariomycetes)和散囊菌纲(Eurotiomycetes),相对频率(RF)分别为66.19%和20.45%;优势目为肉座菌目(Hypocreales)、散囊菌目(Eurotiales)和格孢腔菌目(Pleosporales),相对频率分别为55.4%、17.61%和9.66%;优势属为镰刀菌属(Fusarium)、青霉属(Penicillium)、木霉属(Trichoderma)、未鉴定属3、帚枝霉属(Sarocladium)、未鉴定属2、弯孢属(Curvularia)和突脐蠕孢属(Exserohilum),相对频率分别为32.39%、15.06%、13.35%、5.11%、3.98%、3.41%、3.13%和2.84%,后5个属的相对频率未超过10%,其优势不明显。多样性指数和均匀度系数结果表明,南宁地区坛洛镇TL2样地和锣圩镇LX样地的香蕉根系内生真菌种群多样性较丰富,群落分布较均匀。相似度系数分析显示,钦州地区大成镇2个样地(DC1、DC2)间香蕉根系内生真菌种群组成相似度最高(C_s=0.67)。不同采样点的地理环境和气候条件给香蕉提供了不同的生境,是影响香蕉根系内生真菌种类组成及多样性差异的主要因素之一。     

广西香蕉根系内生真菌的群落组成与多样性

本研究对广西香蕉主产区的香蕉根系样本进行内生真菌分离,采用形态学与ITS序列分析相结合的方法进行菌株鉴定,开展其物种组成与多样性分析,对了解广西香蕉与其根部内生真菌间的关系以及探索其内生真菌功能具有重要意义。从168个香蕉根段中共分离获得352株内生真菌,分别归属于5纲17目34科43属62个分类单元,不同分类单元的代表菌株中,有41株菌株能够产生分生孢子(66.13%)。其中,优势纲为粪壳菌纲(Sordariomycetes)和散囊菌纲(Eurotiomycetes),相对频率(RF)分别为66.19%和20.45%;优势目为肉座菌目(Hypocreales)、散囊菌目(Eurotiales)和格孢腔菌目(Pleosporales),相对频率分别为55.4%、17.61%和9.66%;优势属为镰刀菌属(Fusarium)、青霉属(Penicillium)、木霉属(Trichoderma)、未鉴定属3、帚枝霉属(Sarocladium)、未鉴定属2、弯孢属(Curvularia)和突脐蠕孢属(Exserohilum),相对频率分别为32.39%、15.06%、13.35%、5.11%、3.98%、3.41%、3.13%和2.84%,后5个属的相对频率未超过10%,其优势不明显。多样性指数和均匀度系数结果表明,南宁地区坛洛镇TL2样地和锣圩镇LX样地的香蕉根系内生真菌种群多样性较丰富,群落分布较均匀。相似度系数分析显示,钦州地区大成镇2个样地(DC1、DC2)间香蕉根系内生真菌种群组成相似度最高(C_s=0.67)。不同采样点的地理环境和气候条件给香蕉提供了不同的生境,是影响香蕉根系内生真菌种类组成及多样性差异的主要因素之一。     

野生稻和非洲栽培稻抗稗草作用研究初报

 盆栽试验测定了22份野生稻和9份非洲栽培稻对无芒稗的抑制效果。发现野生稻DY12 和DY16存在显著的抗性作用，它们对无芒稗的苗数抑制率分别达到46.1%和47.0%，对无芒稗植株鲜重抑制率分别达到66.8%和72.3%。非洲栽培稻FZ24也表现出良好的防治无芒稗效果，无芒稗苗数抑制率和植株鲜重抑制率分别达到41.7%和65.7%。     

稗草病原菌防御性接种防治稻瘟病研究初报

 用稗草病原菌互格交链孢菌、弯孢菌、禾长蠕孢菌稗草专化型和尖角突脐孢菌在实验室人工智能气候箱防御性接种感稻瘟病的水稻品种原丰早，预接种后1、2、3、5和7 d分别挑战接种强致病力的稻瘟病菌“中A1”和“中B1”小种。结果表明，与对照相比，稗草病原菌防御接种后，稻瘟病病斑数减少，病斑减少率在35.59%~80.00%，病情指数明显降低，防效显著提高，达53.08%~81.56%。稗草病原菌挑战接种后对水稻秧苗无明显副作用。     

干旱胁迫及复水下朱槿生长及根际土壤微生物多样性的变化特征

以朱槿品种‘紫牡丹’为试验材料,采用盆栽试验,研究了苗期重度干旱胁迫及复水对其根系生理特性的影响,并运用高通量测序技术分析干旱胁迫及复水下朱槿根际土壤微生物多样性的变化特征。结果显示：与正常处理（CK）相比,重度干旱胁迫及复水处理（T2）的总根长、根表面积及根尖数等根系生长指标呈现显著减少的结果,但与重度干旱胁迫（T1）处理相比,均显著增加。通过对朱槿根际土壤样品中细菌群落结构的研究发现,属分类水平上,厌氧绳菌属（Anaerolineaceae）,酸杆菌属（Acidobacteria）、酸微菌属（Acidimicrobiales）、幽门螺杆菌属（Sphaerobacter）、链霉菌属（Streptomyces）等是不同处理土壤样品中的优势菌群。T1处理下的嗜青霉属（Algiphilus）、奥利螺旋菌属（Aureispira）、绿线菌属（Chloronema）、扁棒壳属（Acrospermum）为不同处理下的特殊细菌。真菌方面,属的分类水平上发现,粪壳菌属（Sordariale）、散囊菌属（Eurotiales）、拟青霉属（Pseudallescheria）、格孢腔菌属（Pleosporales）、枝孢霉属（Cladosporium）等是不同处理土壤样品中的优势菌群;T1和T2处理下的样品中,侧角藻属（Goniomonas）、齿盘菌属（Lamprospora）和索罗迪夫斯菌属（Sorodiplophrys）为不同处理下的特殊真菌属。其中,有促生作用的细菌如酸微菌属( Acidimicrobium)、厌氧绳菌属（Anaerolineaceae）嗜青霉属（Algiphilus）以及具有一定生防作用真菌如拟青霉属（Pseudallescheria）、枝孢霉属（Cladosporium）等均可以合理的应用在农业生产中,为植物的抗干旱胁迫以及提高朱槿在干旱胁迫下的水分利用做出贡献。     

Introduction of a fungal NADP(H)-dependent glutamate dehydrogenase (gdhA) improves growth,grain weight and salt resistance by enhancing the nitrogen uptake efficiency in forage rice

We report the effect of the introduction of a fungal glutamate dehydrogenase gene (gdhA) into forage rice (cv. Momiroman) by analyzing the transgenic rice plants in terms of growth, source function, and nitrogen contents. NADP (H)-dependent glutamate dehydrogenase activities in the gdhA-transgenic lines were markedly higher than those in non-transgenic control plants. Plant growth analysis at the seedling stage revealed that the leaf area and shoot and root dry weights of the high gdhA-expressors were higher than those of control plants under both high (high N) and low nitrogen (low N) conditions. These results suggested that the source ability was enhanced by the gdhA introduction. This was supported by the fact that the net photosynthesis rate at the heading stage was also higher in transgenic than in control leaves. Furthermore, under both high and low N conditions, the nitrogen contents in the shoots and roots, at seedling and grain-harvest stages, were significantly higher in high gdhA-expressors than in control plants, indicating that nitrogen uptake was higher in transgenic than in control plants. At the harvest stage, the high gdhA-expressors exhibited greater panicle and spikelet numbers per plant compared with control plants, resulting in higher grain weight, under the high N conditions. In addition, gdhA expression in forage rice significantly enhanced their tolerance to salt stress compared to control plants. The present study showed that the introduction of a fungal gdhA into forage rice could lead to higher source ability, better growth and higher grain weight by enhancing nitrogen uptake efficiency.     

Differential Sensitivity of Rice Cultivars to Salinity and Its Relation to Ion Accumulation and Root Tip Structure

Abstract

Effects of NaCl on the growth, ion content, root cap structure and Casparian band development were examined in four rice (Oryza sativa L.) cultivars with different salt resistance (salt-sensitive indica-type IR 24 and japonica-type Nipponbare and salt-resistant indica-type Nona Bokra and Pokkali). Experiments were conducted to find the differences in salinity resistance during early seedling and developed seedling stages among the cultivars. For salinity treatment, sodium chloride (NaCl) was added to nutrient solution at concentrations of 0, 25 and 50 mM for 7 days from germination to the 7th day (early seedling stage) or from the 7th day to 14th day (developed seedling stage). Growth inhibition by salinity was more prominent in the early seedling stage than in the developed seedling stage. Based on the growth, the order of the sensitivity was IR24 > Nipponbare > Nona Bokra > Pokkali. The growth of NaCl-treated rice cultivars relative to control was significantly and negatively correlated with the Na⁺ content and Na⁺/K⁺ ratio in roots and shoots in both stages. Scanning electron microscopic observation revealed that the root cap tissues proliferated and extended to the basal part of the root tip by salinity. The length of root cap was, however, reduced by 50 mM NaCl in sensitive cultivars due to peeling off. An endodermal Casparian band was formed in the basal region of the root tip. Development of the Casparian band was more prominent in sensitive cultivars than in tolerant cultivars. Root cap proliferation might be related to NaCl resistance in rice seedlings, but the Casparian band may not function efficiently in Na⁺ exclusion. Essentially the present results suggest that exclusion of Na⁺ from roots plays a critical role in expression of Na⁺ resistance in rice seedlings and the root cap is important for Na⁺ exclusion.     

Phytochromes are Involved in Elongation of Seminal Roots and Accumulation of Dry Substances in Rice Seedlings

Phytochromes have been reported to play important roles in seedling de-etiolation and flowering in rice.To identify the roles of phytochromes in regulating root growth and accumulation of dry substances,the lengths of seminal roots and the dry weights of seedlings were measured in the wild type as well as the phytochrome A(phyA) and phytochrome B(phyB) mutants grown under different conditions.When the whole seedlings were exposed to white light,the elongation of the seminal roots was significantly photoinhibited in the wild type,whereas this inhibitory effect was clearly reduced in the phyA and phyB mutants.When the roots of the seedlings were blocked from white light,the phyA and phyB mutants exhibited significantly longer seminal roots than the wild type.These results suggest that both the root-localized and shoot-localized PHYA and PHYB are involved in the photoinhibition of seminal root elongation in rice seedlings.By measuring the dry weights of roots and shoots,it is revealed that PHYB positively regulates the accumulation of dry substances in shoots,however,PHYA exerts the contrary effects on the accumulation of dry substances in roots and shoots of rice seedlings.     

Peptide Transporter OsNPF8.1 Contributes to Sustainable Growth under Salt and Drought Stresses,and Grain Yield under Nitrogen Deficiency in Rice

Peptide transport is important for plant tissues where rapid proteolysis occurs, especially during germination and senescence, to enhance redistribution of organic nitrogen (N). However, the biological role of peptide transporters is poorly investigated in rice. We characterized the function of the peptide transporter OsNPF8.1 of rice nitrate transporter 1/peptide transporter family (NPF). Ectopic expression of OsNPF8.1 in yeast revealed that OsNPF8.1 encoded a high-affinity di-/tri-peptide transporter, and the osnpf8.1 mutants had a lower uptake rate of the fluorescent-labelled dipeptide c in leaves of rice seedlings. Histochemical assays showed that OsNPF8.1 was highly expressed in mesophyll cells and vascular parenchyma cells, but not detected in root hairs and epidermises. Expression of OsNPF8.1 was induced by N deficiency, drought, NaCl and abscisic acid, and kept at a high level in senescing leaves. Under N deficiency conditions, compared with the wild type Zhonghua 11, the osnpf8.1 mutants grew slower at the seedling stage, and had lower grain yield and lower N content in the grains. In contrast, OsNPF8.1-over-expressing rice (OsNPF8.1-OE) grew faster at the seedling stage and had a higher grain yield. The osnpf8.1 seedlings were less tolerant to salt and drought stresses. These results suggested that stress-induced organic N transportation mediated by OsNPF8.1 might contribute to balance plant growth and tolerate to salt/drought stress and N-deficiency.     

Mechanisms for coping with submergence and waterlogging in rice

Background

Oligopeptide transporters (OPTs) play important roles in the mobilization of organic nitrogenous compounds and usually associate with tissues that show signs of rapid protein hydrolysis, such as germinating seeds and senescing leaves. This study is to investigate rice OPT genes.

Results

A total of sixteen OsOPT genes (Os for Oryza sative L.) were identified in the rice genome, which were then classified into six sections that belong to two subfamilies (the PT and YSL subfamily). The major mechanisms for evolutionary expansion of the sixteen genes during the rice genome evolution include segmental and tandem duplication. Calculation of the duplication event dates indicated that the sixteen genes originated from nine original OsOPT genes, and the duplication events could be classified into three evolutionary stages. The first evolutionary stage occurred approximately 50 million years ago (Mya) and involved the evolution of four new genes. The second evolutionary stage was approximately 20 Mya and was marked by the appearance of two new genes, and the third evolutionary stage was approximately 9 Mya when two new genes evolved. Mining of the expression database and RT-PCR analysis indicated that the expression of most duplicated OsOPT genes showed high tissue specificities. Diverse expression patterns for the sixteen genes were evaluated using both semi-quantitative RT-PCR and the MPSS data. Expression levels of some OsOPT genes were regulated by abiotic and biotic stresses suggesting the potential involvement of these gene products in rice stress adaptation. Five OsOPT gene mutants showed abnormal development and growth, the primary analysis of five OsOPT gene mutants suggested that they may be necessary for rice development.

Conclusions

These results suggested that rice-specific OsOPT genes might be potentially useful in improving rice.     

Identification,ecological evaluation and phylogenetic analysis of non‐symbiotic endophytic fungi colonizing timothy grass and perennial ryegrass grown in adjacent plots

Non‐systemic endophytes coexist with grasses and produce positive or negative effects for the host. In agricultural grasses, endophytes such as Epichloë spp. (formerly: Neotyphodium spp.) enhance the biometric parameters and agricultural value of grass biomass and seeds. Some endophytic fungi produce active substances that exert a negative influence on grass‐fed livestock. There is a general scarcity of studies investigating other endophytic fungi, the species composition of fungal communities, fungal species capable of colonizing different grasses and endophyte transfer between grass taxa. This study aims to fill in the existing knowledge gap by describing the relationships between fungal species and grass species. Timothy grass (Phleum pratense L.) is more readily colonized by endophytic fungi than perennial ryegrass (Lolium perenne L.), and the ratio of fungi isolated from the above species was determined at 3:1. Ecological indicators, especially diversity, were also higher in the fungal community colonizing timothy grass. The vast majority of the isolated fungi were ascomycetes. In addition, two Basidiomycota isolates and three Oomycota isolates (Phythium acanthicum) were also obtained from timothy grass. The most prevalent fungal species were Alternaria alternata, Microdochium bolleyi and Epicoccum nigrum. An analysis of minisatellite DNA regions revealed high levels of genetic polymorphism in A. alternata, whereas the remaining isolates were characterized by low levels of genetic variation or genetic homogeneity. The transfer of endophytic fungi between grass species was determined, which was one of the most important observations made in the study. The Sørensen–Dice coefficient reached 50%, which indicates that all fungal species isolated from perennial ryegrass are capable of colonizing timothy grass.     

浸种剂对水稻种子微生物群落结构的影响

以常规粳稻秀水134为材料,设置清水浸种（CK）和咪酰胺浸种（Soak）两个处理,采用16S rRNA扩增子测序和分离培养等方法,研究浸种剂咪酰胺对水稻种子微生物群落结构的影响。结果表明,与CK相比,Soak处理水稻种子表面真菌数目显著减少,而对水稻种子内细菌群落多样性和组成,包括细菌群落Shannon 指数、Chao1 指数、Observed OTUs、β多样性以及优势菌群相对丰度没有显著影响。可见,在农业生产中,咪酰胺浸种作为防治水稻种传病害的措施对种子内生菌群没有显著影响。     

外源一氧化氮对盐胁迫下水稻根部脂质过氧化的缓解作用

 在100 mmol/L NaCl的胁迫条件下，研究了两种浓度的一氧化氮供体硝普钠（sodium nitroprusside，SNP）处理对水稻幼苗根部脂质过氧化的影响。低浓度（10 μmol/L）的SNP处理明显缓解盐胁迫下水稻幼苗根组织膜脂过氧化产物MDA的累积，显著提高可溶性蛋白含量，并诱导根系APX、POD和SOD活性的上升；而高浓度（50 μmol/L）SNP处理的效果则基本相反。表明外源低浓度NO可以通过提高盐胁迫下水稻幼苗根组织的抗氧化能力来缓解氧化损伤。     

Ionomic Profiling of Rice Genotypes and Identification of Varieties with Elemental Covariation Effects

Ionomic profiles are primarily influenced by genetic and environmental factors. Identifying ionomic responses to varietal effects is necessary to understand the ionomic variations among species or subspecies and to potentially understand genetic effects on ionomic profiles. We cultivated 120 rice (Oryza sativa) varieties to seedling stage in identical hydroponic conditions and determined the concentrations of 26 elements (including 3 anions) in the shoots and roots of rice. Although the subspecies effects were limited by the genus Oryza pre-framework and its elemental chemical properties, we found significant differences in ionomic variations in most elements among the aus, indica and japonica subspecies. Principal component analysis of the correlations indicated that variations in the root-to-shoot ionomic transport mechanisms were the main causes of ionomic differences among the subspecies. Furthermore, the correlations were primarily associated with the screening of varieties for elemental covariation effects that can facilitate breeding biofortified rice varieties with safe concentrations of otherwise toxic elements. The japonica subspecies exhibited the strongest elemental correlations and elemental covariation effects, therefore, they showed greater advantages for biofortification than the indica and aus subspecies, whereas indica and aus subspecies were likely safer in metal(loid) polluted soils. We also found that geographical and historical distribution significantly defined the ionomic profiles. Overall, the results of this study provided a reference for further association studies to improve the nutritional status and minimize toxicity risks in rice production.     

植物内生菌对大豆促生长和抗胁迫作用的研究进展

植物内生菌是指在其生活史或一段生活史在植物体内并对植物无明显病害的一类微生物。内生菌不仅具有自身特有的生存机制,而且对植物的生长发育具有重要作用。随着分子生物学技术的不断进步,人们将分离的植物内生菌转染于大豆植株,通过对大豆在遭受生物和非生物胁迫下叶片光合参数、酶活性、相关基因表达水平及生物量的测定,来分析植物内生菌对大豆生长的影响。本研究综述了植物内生菌的多样性以及近年来植物内生菌在非生物胁迫下如干旱、盐胁迫、重金属等和生物胁迫下如病虫害对大豆生长发育影响的研究进展,并对内生菌应用的前景进行了展望。