The relationship between soil copper content and copper resistance in yeast of an ultisol in midwestern Nigeria

Yeast isolates were obtained from the brewer's stock of the Guinness brewery in Benin City, midwestern Nigeria, and from local sources such as mango and sugar cane. The fruits were exposed to the immediate soil environment in eleven selected sites in the Ugbowo and Ikpoba Hill areas of Benin City, Edo State of midwestern Nigeria. A total of twenty-seven yeast isolates were obtained. Fourteen isolates were identified as Saccharomyces cerevisiae and 13 as S. carlsbergensis. Analysis of resistance to copper sulphate revealed that the two brewer's yeast isolates were resistant to 3.5 mM and 4.2 mM CuSO₄, respectively, while the local yeasts were resistant to higher concentrations ranging from 6.5 to 16.5 mM. The percentage copper sulphate resistance of yeast isolates obtained from Mangifera indica ranged from 52.4 to 73.8%, while the percentage copper sulphate resistance of yeast isolates obtained from Saccharum officinarum ranged from 51.8 to 62.6%. The two brewer's yeast isolates (BY2 and BY4) had a percentage CuSO₄ resistance of 32.4 and 38.5%, respectively. Comparison of soil copper concentration and copper resistance levels in selected yeast isolates indicated that the soil copper concentrations generally influenced the ability of yeasts to resist copper.     

Soil-based screening for iron toxicity tolerance in rice using pots

The objective of this study was to assess the reliability of pot-based screening method for iron (Fe) toxicity tolerance in rice using soils from hot spots. Five lowland rice varieties with known reaction to Fe toxicity were grown in pots in a screen house for three seasons. Fe-toxic soils from two hot spot fields – Edozighi, Nigeria and Niaouli, Benin were used and soil from Africa Rice Center (AfricaRice) experimental farm, Cotonou, Benin was included as control. Leaf bronzing score (LBS) was determined at different stages, and grain yield was determined at maturity. Heritability was estimated using data across the three seasons. High heritability was recorded for LBS and grain yield. Grain yield reduction in stress treatment relative to control varied from 15 to 56% depending on the variety and soil. Bao Thai, Suakoko 8, and WITA 4 had better performance under Fe toxicity in terms of LBS, yield and relative yield reduction, whereas Bouake 189 and IR64 had poorer performance. Grain yield and LBS were significantly correlated but negatively at 60 days after sowing (DAS). Overall, the results found in this experiment were consistent with previous field studies. Therefore, pot screening using soils from hot spots can be used by rice breeding programs to reliably assess Fe toxicity tolerance ex situ.     

Diversity and phylogeny of basidiomycetous yeasts from plant leaves and soil: Proposal of two new orders,three new families,eight new genera and one hundred and seven new species

Nearly 500 basidiomycetous yeast species were accepted in the latest edition of The Yeasts: A Taxonomic Study published in 2011. However, this number presents only the tip of the iceberg of yeast species diversity in nature. Possibly more than 99 % of yeast species, as is true for many groups of fungi, are yet unknown and await discovery. Over the past two decades nearly 200 unidentified isolates were obtained during a series of environmental surveys of yeasts in phyllosphere and soils, mainly from China. Among these isolates, 107 new species were identified based on the phylogenetic analyses of nuclear ribosomal DNA (rDNA) [D1/D2 domains of the large subunit (LSU), the small subunit (SSU), and the internal transcribed spacer region including the 5.8S rDNA (ITS)] and protein-coding genes [both subunits of DNA polymerase II (RPB1 and RPB2), the translation elongation factor 1-α (TEF1) and the mitochondrial gene cytochrome b (CYTB)], and physiological comparisons. Forty-six of these belong to 16 genera in the Tremellomycetes (Agaricomycotina). The other 61 are distributed in 26 genera in the Pucciniomycotina. Here we circumscribe eight new genera, three new families and two new orders based on the multi-locus phylogenetic analyses combined with the clustering optimisation analysis and the predicted similarity thresholds for yeasts and filamentous fungal delimitation at genus and higher ranks. Additionally, as a result of these analyses, three new combinations are proposed and 66 taxa are validated.     

Assessment of levels of resistance of cotton cultivars to isolates of Xanthomonas malvacearum (E.F. Smith) Dowson in Nigeria

Nine cotton cultivars were assessed for resistance to bacterial blight by inoculation of the mid-veins of leaves of seedlings at the four- to six-leaf stage with six isolates of Xanthomonas malvacearum (E.F. Sm.) Dowson, obtained from the three cotton-growing zones of northern Nigeria. The length of lesions 15 days after inoculation formed the basis of assessment. REBA B-50 and RASA (76)101 were highly resistant, while RSA(68)27 and BJA-592 were classified as resistant. The moderately resistant group consisted of Arkansas 52-21, Samaru 77 and Samaru 72. Samaru 71 was less susceptible than Samaru 26J, the susceptible control. There were also differences in virulence amongst the six isolates of X. malvacearum used in the test, suggesting the possible presence of races of the pathogen.     

Comparative efficiency of chemical compounds for in vitro and in vivo activity against Clavibacter michiganensis subsp. michiganensis, the causal agent of tomato bacterial canker

Bacterial canker of tomato caused by Clavibacter michiganensis subsp. michiganensis produces considerable economic losses in many countries because effective control measures are lacking. The extent to which bactericides control this disease effectively is low and has not yet been well documented for Southern European conditions. In this study the bactericidal effect of several products on this pathogen was assessed in vitro and in vivo in tomato plants under greenhouse conditions. Seven antibacterial substances (bronopol, copper sulphate, kasugamycin, oxolinic acid, oxytetracycline, streptomycin and 8-hydroxy-quinoline), three commercial formulates (Antibak RZ, an oligoelements mixture containing copper plus zinc; Orthopol, a potassium soap; and Param, a resistance inductor) and combinations thereof were tested. In vitro assessment showed that minimal inhibitory concentration (MIC) of antibacterial substances was between 4–8 μg ml⁻¹, except for copper sulphate with a MIC value of 150 μg ml⁻¹ and kasugamycin, which was not active at 500 μg ml⁻¹. MIC values of commercial formulates ranged between 5 and 40 μl ml⁻¹. Furthermore, combinations of 8-hydroxy-quinoline+copper sulphate, 8-hydroxy-quinoline+Antibak RZ, streptomycin+Antibak RZ and streptomycin+Orthopol showed a synergistic effect at sub-inhibitory concentrations. Treatments containing copper sulphate greatly reduced disease symptoms on plants sprayed with the bacteria, whereas streptomycin was less effective. In two independent trials, the percentage of leaves showing symptoms was significantly lower (2.4% and 11.9%) after treatment with copper sulphate combined with 8-hydroxy-quinoline at half-dose, than in inoculated controls (75.1% and 59.6%). These results were better than copper sulphate alone. However, plants inoculated by pricking rapidly developed systemic infection, which no product managed to control significantly, although several treatments did reduce symptoms. We conclude that copper sulphate combined with 8-hydroxy-quinoline may be useful in controlling external symptoms of this disease in greenhouses, and is environmentally friendly, reducing the amount of copper applied to crops.     

Assessing Silicon Availability in Soils of Rice-Growing Lowlands and Neighboring Uplands in Benin and Nigeria

Silicon(Si) is known as a beneficial nutrient in the cultivation of rice, playing a key role in photosynthesis enhancement, lodging resistance and tolerance to various environmental stress. The present study aimed to examine available Si content in both lowland soils(n = 29) and neighboring upland soils(n = 21) collected from Benin and Nigeria and to evaluate the validity of the assessment results through a pot experiment. Our results revealed that the acetate-buffer method predicted Si concentration in rice straw at the harvest stage(R~2 = 0.68, P < 0.01) better than the anaerobic-incubation method(R2 = 0.31, P > 0.05), and 76% of the uplands and 38% of the lowlands were deficient(< 50 mg/kg) in acetate-buffer soluble Si. These findings suggest that the Si-deficiency soils prevail across the study area, making rice plants starved for Si and prone to environmental stress.     

Effects of temperature on copper resistance in daf-21 mutant and Hsp90 expression of Caenorhabditis elegans

To determine the effects of temperature alterations on copper toxicity and stress response in Caenorhabditis elegans, an aquatic acute toxicity test was utilized to combinations of four temperature levels (15, 20, 25, and 30°C) and four copper concentrations (0, 0.013, 0.13, and 1.3 mM). Endpoints used included 24-h median lethal concentrations (LC50) value, and 90-kDa heat shock proteins (Hsp90) induction. Results showed a significant acceleration in the mortality with increasing temperature and depressed expression in Hsp90 of the presence of copper. Data on LC50 revealed that simultaneous exposure to both copper and heat stress (30°C) was severe. In contrast, subdued reactions to copper were observed in adult nematode exposed to low temperature (15°C). We have discovered that daf-21 mutation adults result in decreased Cu²⁺ resistance in a 24 h toxicity assay. Significantly weak expression of Hsp90 in C. elegans was observed at high copper stress as LC50 concentration irrespective of temperatures. These results suggest acclimation temperatures caused variations in copper stress of C. elegans, and Hsp90 expression exhibited greater severity with increasing copper concentration. The present study confirms that temperature effectively confounds copper toxicity and needs to be considered for the accurate prediction and assessment of copper-induced toxicity in nematode.     

天然胶乳的常压氢化及产物性能

应用NH4H40（水合腓）/H02/CuSO4催化体系在常压下使天然胶乳氢化制备氢化天然橡胶,结果表明硬脂酸钠、五水硫酸铜、水合腓用量及反应温度对HNR饱和度有显著的影响,当没有外加硬脂酸钠,铜离子与天然橡胶干胶分子链上双键的摩尔数之比为1∶1000,水合腓与干胶分子链上双键的摩尔数之比为1.4∶1,反应温度45℃时,HNR饱和度可达到64.6%。天然橡胶氢化后,其硫化胶力学性能得到改善,耐老化性能显著提高。     

香蕉炭疽病优势拮抗酵母菌的分离及筛选

采用稀释平板法和平板划线法从8个不同品种的香蕉果实上分离纯化酵母菌,并将其与香蕉炭疽病原菌进行平板对峙培养及离体防效试验,以筛选优势拮抗酵母菌.结果表明:从香蕉果实上共分离纯化酵母菌329株;平板对峙培养后获得3株拮抗香蕉炭疽病原菌作用明显的酵母菌;离体防效试验筛选出1株拮抗效果较好且稳定的优势拮抗酵母菌Z-BR-16,以无菌水为对照,接种7d后,其1.0×108 CFU/mL菌液对香蕉炭疽病的抑制率为75.94％.     

Variation among foliar isolates of Colletotrichum sublineolum of sorghum in Nigeria

Foliar anthracnose, caused by Colletotrichum sublineolum, is a major disease of sorghum in Nigeria. Pathogenic diversity was studied among foliar isolates of C. sublineolum collected from sorghum cultivars in farmers fields in the Sahel, Sudan, northern Guinea and southern Guinea zones of Nigeria during the 1997 crop season. For the study a total of 50 isolates were identified based on typical symptom types and cultural characteristics. On the basis of growth in culture and morphological characteristics, the isolates were classified into nine morphological groups (MGs). Pathogenicity tests were done on a set of known sorghum differential lines by inoculating pot-grown seedlings in a greenhouse. On the basis of disease reaction and disease severity scores on the differential lines, the 50 isolates were classified into seven pathogenic groups (PGs). Sixteen representative isolates of the MGs and the PGs were further evaluated for virulence and aggressiveness on the differential lines and were classified into five distinct groups using the centroid method of cluster analysis. The existence of five races of C. sublineolum in major sorghum growing zones of Nigeria is suggested.     

Evaluation of fungicides to control Cylindrocarpon liriodendri and Cylindrocarpon macrodidymum in vitro, and their effect during the rooting phase in the grapevine propagation process

The efficacy of 14 selected fungicides against Cylindrocarpon liriodendri and Cylindrocarpon macrodidymum was evaluated in vitro by testing their effect on mycelial growth and conidial germination. Carbendazim, hydroxyquinoline sulphate, imazalil, and prochloraz were the most effective fungicides in reducing mycelial growth in both Cylindrocarpon species. Captan, copper oxicloride, didecyldimethylammonium chloride and thiram were the most effective to inhibit conidial germination of both species. A pot assay was also conducted with captan, carbendazim, copper oxychloride, didecyldimethylammonium chloride, hydroxyquinoline sulphate, imazalil and prochloraz in order to determine their potential to prevent infections caused by C. liriodendri and C. macrodidymum during the rooting phase in the grapevine propagation process. All fungicides significantly decreased the root disease severity values in both species compared with control treatment, with the exception of imazalil in C. macrodidymum. In the case of the percentage of reisolation, all values were lower than those obtained for the control treatment, but only captan, carbendazim and didecyldimethylammonium chloride were significantly different in the case of the cuttings inoculated with C. liriodendri, and prochloraz in the case of those inoculated with C. macrodidymum.     

蓖麻三磷酸甘油脱氢酶基因 (RcGPDH)的克隆及功能分析

为了阐明蓖麻三磷酸甘油脱氢酶基因（glycerol-3-phosphate dehydrogenase, RcGPDH）在蓖麻油累积过程中的作用,本研究根据已报道的蓖麻种子表达序列标签（Expressed Sequence Tags,EST）设计引物,通过RACE（rapid-amplification of cDNA ends)方法克隆蓖麻RcGPDH基因的全长并对其序列进行分析,构建了该基因的酵母表达载体PYES2.1/V5-His-TOPO-RcGPDH,以载体PYES2.1/V5-His/lacZ质粒DNA为对照,转化酵母野生型菌株BY4742,运用分光光度法测定转基因酵母的生长曲线,通过香草醛法测定稳定生长期的转基因酵母的油脂含量。结果表明,转基因菌株比转空载体对照菌株生长慢,两者均在培养18h后进入平台期;两个菌株的油脂含量没有明显的差别,表明RcGPDH基因对酵母油脂的累积没有起到积极的作用,在蓖麻种子中可能还存在另一个GPDH同源基因参与TAG的合成。     

甘蔗渣啤酒糟高效转化平菇试验研究

以甘蔗渣为主料,啤酒糟为主要辅料,通过研究姬菇6号、新选700、特抗650和夏抗50菌丝生长速度、长势和生物转化率等指,标优化出比较适合蔗渣栽培的平菇品种和栽培配方。正交实验极差结果显示,影响4个平菇生物转化率的主次因素为啤酒糟＞麸皮。实验结果表明,添加适宜的麸皮是蔗渣栽培平菇增产的关键;姬菇6号、新选700、特抗650和夏抗50均在配方4(A2B3)上生物转化率最高,即啤酒糟15%、麸皮10%的配方上生物转化率最大,其生物转化率分别为160.06%、140.89%、178.75%和125.87%。结合4个菌株出菇时的农艺性状得出,姬菇6号比较适合以甘蔗渣为主料,啤酒糟为辅料的培养基栽培。     

Expansion profiles of wheat doughs fermented by seven commercial baker's yeasts

Commercial baker's yeast consists of Saccharomyces cerevisae, however the strain can vary in each baker's yeast, which might influence the dough fermentation time. The scope of this research was to investigate the dough expansion of wheat doughs fermented by seven commercial baker's yeasts at different yeast concentrations (2.88·10¹¹, 5.76·10¹¹ and 8.64·10¹¹ colony forming units/kg flour) and fermentation temperatures (5 °C, 15 °C, 25 °C and 35 °C). Dough expansion was investigated by monitoring the dough height and it was found to be described well by a first order kinetic model. Doughs fermented with four of the seven yeasts generally had higher kinetic rate constants and hence shorter fermentation times compared to fermentation with the other three yeasts. The shortest fermentation times were found for doughs fermented at 25 °C and the highest yeast concentration, a trend found for all the yeasts tested. The differences in the kinetic rate constants indicate a differentiation in yeast strain among the commercial baker's yeasts emphasising the great importance of the choice of baker's yeast for the dough fermentation time.     

云南高海拔粳稻区白叶枯病菌致病力差异分析

云南高海拔粳稻区白叶枯病危害日益严重,为了探明该区域白叶枯病菌致病力差异,对白叶枯病进行有效防控。利用15个水稻白叶枯病菌鉴别品种,对采集自海拔1800 m以上稻区11个水稻品种上的32份菌株进行致病力研究。结果发现,致病力最强的菌株是楚雄州的CX28-3和CX30-1,致病率为73.33%;最弱的是大理州剑川县的JC12-2,致病率为0。在高海拔粳稻区,菌株的致病力分化与采集地的海拔高度无关,却与地理距离、采集品种的推广面积有关;而菌株的致病型频率与其采集地的海拔、经纬度、采集品种的推广面积的相关性均不显著。鉴别品种毫糯扬(含新基因)、IRBB14(Xa14)、IRBB4(Xa4)和Tetep(Xa2,Xa16)对所有参试菌株表现为高抗或抗。因此,这些品种内所含的抗性基因值得在云南高原粳稻育种和生产中应用,特别是云南地方稻种毫糯扬,更应加强其新抗病基因的定位和克隆,以为品种选育提供新的抗原。     

超级稻品种中早39的稻瘟病抗谱测定

利用采自全国12个省市、分属A~G 7个群40个生理小种的146个菌株对中早39进行了稻瘟病抗谱测定。结果显示,中早39对籼型小种的平均抗谱为82.9%,对粳型小种的平均抗谱为71.2%。中早39对不同省市的稻瘟病菌株的抗谱是不一致的,对黑龙江、辽宁、陕西等3个省份菌株的抗谱较低,均为40.0%;对陕西以南9个省(市)菌株的平均抗谱为82.8%。其中,中早39对浙江、贵州和广西的菌株抗谱分别为92.9%、93.1%、100%,说明中早39在这3个省份可以作为稻瘟病抗性育种的抗源使用。     

Efficacy and environmental fate of copper sulphate applied to Australian rice fields for control of the aquatic snail Isidorella newcombi

Copper sulphate pentahydrate (CuSO₄·5H₂O) is widely used for controlling Isidorella newcombi, an aquatic snail that causes substantial damage to rice crops in southeastern Australia. We conducted field trials on a Birganbigil clay loam soil that demonstrate high levels of efficacy against adult I. newcombi (95% mortality at 6.38 kg ha⁻¹ CuSO₄·5H₂O (1.14 mg Cu L⁻¹)). Dissolved copper fell below the detection limit (0.02 mg Cu L⁻¹) between 7 and 20 d after spraying at application rates up to 2.16 mg Cu L⁻¹ (12 kg ha⁻¹ CuSO₄·5H₂O). Total copper concentrations in the water column fell below the detection limit (0.007 mg Cu L⁻¹) 7–12 d after spraying at initially applied concentrations of 0.52–1.12 mg Cu L⁻¹, but remained detectable (0.01–0.02 mg Cu L⁻¹) until 30 days after spraying (the conclusion of monitoring) when applied at higher initial concentrations (1.18–2.16 mg Cu L⁻¹). There was a strong positive correlation (r² = 0.90, P < 0.001) between copper application rate and copper concentrations in surface sediments 30 d after spraying. Bioassays with immature snails using three different test soils beneath irrigation water showed that underlying soil type strongly influenced the response of snails to applied copper, with significant (P < 0.05) differences between LC₉₀ values which ranged from 0.41 to 1.04 mg applied Cu L⁻¹. Laboratory studies showed that dissolved copper concentrations remained significantly higher (P < 0.05) in the water column above the soil that had the most deleterious effect on copper toxicity. Dissolved organic carbon concentrations were significantly (P < 0.05) higher in both this soil and in the overlying water in the corresponding bioassay system, and correlated more closely with LC₉₀ values than other water chemistry parameters such as total hardness. Our results support the ongoing use of a variable copper application rate of 6–12 kg ha⁻¹ CuSO₄·5H₂O to allow for site-specific variations in efficacy, and suggest that variations in the release of dissolved organic carbon compounds from flooded soils may be a key factor moderating copper toxicity to I. newcombi in rice fields.     

油菜菌核病菌对腐霉利的抗性诱变及抗药菌株的生物学特性

从江苏省镇江市和扬州市采集菌核病植株的茎,从中分离获得油菜菌核病菌（Sclerotinia sclerotiorum）单菌核菌株。32个野生型菌株药剂敏感性（EC50）频率分布数据显示,病菌对腐霉利的敏感基线EC50值为0.1981 ± 0.0220 µg/mL,MIC（最小抑菌浓度）值为 1.1 ± 0.1595µg/mL。实验未发现田间抗腐霉利菌株。通过室内紫外线和药剂诱导,获得多株高抗腐霉利突变体（EC50>1000µg/mL）。这些抗性突变株经转管培养5~20代后抗药性稳定。它们对同类药剂异菌脲和有机磷类甲基立枯磷也表现高抗,但对苯并咪唑类多菌灵敏感。与野生型敏感菌株相比,抗腐霉利突变株菌丝生长较慢,对油菜茎杆和叶片的致病力均较弱。     

A model of aerobic fungal growth in silage.

The components of a simulation model of mesophilic and thermophilic yeast and mould growth in aerobically deteriorating silage are presented. The purpose of the model is to examine the relative roles of yeasts and moulds in deterioration and the factors affecting aerobic stability. Information for the model was based on literature studies. Growth of the fungi was assumed to be affected by temperature, pH, water activity, and lactic and acetic acid concentrations. The substrates utilized in the model, in order of preference, were water-soluble carbohydrates, ethanol, lactic acid and acetic acid. Gas movement and heat transfer were not considered. Consequently, oxygen and carbon dioxide concentrations were assumed to be those for open air, and the heat of respiration retained in the silage was set as a constant percentage of that released by fungal growth.
Based on the relationships developed for the model, pH affects yeast growth minimally and does not affect mould growth at all. Water activity over the range in silage affects yeast growth more than mould growth, but affects neither one strongly. Undissociated lactic and acetic acids decrease growth rate and may be important factors in silage stability. Compared with moulds, yeast growth rates are less affected by suboptimum temperatures but are more sensitive to temperatures in excess of the optimum.
A succeeding study compares the model with published aerobic deterioration studies and examines the predicted succession of microbial groups and the variation in silage stability as affected by silage parameters, initial temperature, and initial microbial populations.     

Biological control of sheath blight of rice with the fermented product B-916 (Bacillus subtilis) in China

Bacterial isolates of 1274 were obtained from paddy soil, sclerotia of Rhizoctonia solani, lesions of sheath blight (ShB), and rice plants.