对玉米不同品种小斑病发生规律的调查

本试验对4个玉米品种小斑病的发生规律进行了研究。结果表明，发生小斑病的叶片基本上是从下部第1～3张叶片开始逐渐向上蔓延的。在小斑病发生的早期，病情指数的增加主要是由于发病率的增加所引起的，后期主要是由于病级的增加所引起，且品种的抗病性影响了小斑病发生的早晚、轻重以及流行曲线的增长的快慢，抗小斑病的品种发病晚且轻，并且其流行曲线增长较慢，感病的品种与此相反。     

玉米品种小斑病抗性鉴定

小斑病是我省玉米生产上的主要病害,继1966、1967年连续大发生后,小斑病在我省每年都不同程度发生为害。一般中等发生年,感病品种减产两成左右。实践证明,采用抗病品种为主的综合防治措施是经济有效的。为了加快抗病育种的步伐,我们对有关玉米品种对小斑病的抗病性鉴定技术方法进行了试验研究。     

玉米抗小斑病种质资源的筛选鉴定

玉米小斑病(Bipolars Maydis)是世界玉米产区的主要病害之一,1970年曾使美国损失玉米165亿kg,我国的华北玉米区和华南部分玉米区也是该病的主要发生区。该病的流行与大面积种植感病品种密切相关,而防治该病的经济有效措施是选用抗病品种。为此“七五”、“八五”期间国家把玉米种质资源抗小斑病的筛选鉴定列为攻关内容。本文报道1992～1995年的研究结果。     

山东省邹平县玉米黄斑病发生因素探析

黄斑病是近年来玉米生产的重要病害,其危害程度超过大斑病和小斑病。本研究从品种、气象、栽培、环境等多方面探析了其发病规律结果表明：年际间、品种间发病程度差别较大,不同播种基础、不同种植方式、不同地域也存在较大差异,应重点采用农艺措施进行预防。     

不同来源黄早4改良系的抗病性鉴定

１９９１和１９９２年，鉴定１０个黄早４改良系对黄斑病，玉米大、小斑病，丝黑穗病，矮花叶病和青枯病的抗病性，并对玉米褐斑病、粗缩病的发病情况进行了调查。１０个黄早４改良系中有６个对黄斑病的抗性明显增强，其中冀３５、黄４０５２、农大２５６等三个自交系既克服了黄早４不抗黄斑病的缺点，又保持了原黄早４高抗玉米矮花叶病的特性，兼抗性能较好。     

平昌县玉米病虫害种类及防治技术

<正>近年,随着农业生产水平的提高、品种的更换及耕作制度的改变,玉米病虫害的发生和为害呈加重趋势,发生严重的有玉米大斑病、小斑病等,对玉米生产造成了很大影响。1病害的种类与防治1.1玉米大、小斑病玉米大斑病和小斑病主要为害叶片,有时也侵染叶鞘和苞叶,小斑病除为害上述部位外,还可为害果穗。许多地区常将这两种病统称为"玉米斑病"。     

河西走廊制种玉米3种真菌性叶斑病的诊断与识别

玉米大斑病、玉米小斑病和弯孢菌叶斑病是河西走廊制种玉米生育中后期发生的主要叶部病害。为了提高对这3种叶斑病的田间诊断和识别水平,对其发病情况进行了田间调查,归纳总结出3种病害的症状特点,并对引起病害的病原菌进行了分离与鉴定。结果表明,3种叶斑病在发病时期、病斑形态、病斑大小、病状等方面区别明显;在供试的10种玉米自交系品种中,大斑病、小斑病和弯孢菌叶斑病的发病率和病情指数存在明显的差异;分离到引起玉米叶斑病的真菌病原13种,其中玉米弯孢菌叶斑病Curvulairia lunata(Walke)Boedijn、玉米大斑病Exserohilum turcicum(Pass)Leonard et Suggs和玉米小斑病Bipolaris maydis(Nishik.et Miyake)Shoemaker分离率较高。     

贵州主要水稻品种对稻瘟病的抗性监测研究

稻瘟病是我省水稻的主要病害,常年发生面积13．34万hmZ左右,一般减产10o～30o。1982年全省穗瘟大流行,发病面积1333万hmZ,损失稻谷1亿多kg,发病品种主要是庚湘。遵灿三号、桂朝二号、糯谷等常规品种;1993年全省穗瘟又一次大流行,流行面积16．67万hmZ,损失稻谷2．9亿kg,感病品种由以前的常规品种扩展到部分杂交稻品种,且以水稻主栽品种汕优63发生面积最大。大面积栽种感病品种是造成稻瘟病流行的主要原因之一,选栽抗病良种是防治稻瘟病最经济有效的措施。为了摸清我省主要种植的杂交稻品种对稻瘟病的抗性变化,为今后生产上品种…     

不同来源黄早四改良系抗病性鉴定初报

玉米自交系黄早四是北京市农科院70年代初选育成功的。该自交系高抗玉米大、小斑病和矮花叶毒病,株型好,配合力高,70～80年代中期成为我国北方夏玉米区种子生产中骨干自交系。但80年代中期,黄早四发生了黄斑病危害,抽雄后叶片产生大量黄色病斑,迅速扩展、蔓延,到乳熟期全株叶片基本干枯,造成严重减产。但因黄早四具有其它玉米自交系所不能代替的优点,所以在80年代后期相继出现     

拜泉县玉米病害发生现状及防治措施

正黑龙江省拜泉县玉米种植面积广阔。玉米生产形势直接关系着国计民生,经多年攻关研究,拜泉县玉米抗病育种工作已取得巨大成绩,由于推广了抗大、小斑病及丝黑穗病的玉米新品种或杂交新组合,已使大、小斑病及丝黑穗病等老病害得到了有效控制,然而因目前生产中采用的品种或自交系多为单抗性品种,而且种质遗传基础狭窄,致使玉米茎腐病、灰斑病、弯孢菌叶斑病、纹枯病、病毒病等病害发生愈来愈普遍,为害日益加重,严重制约了玉米生产的发展和提高,已成为植     

Biological Activity and Quantification of Suspected Allelochemicals from Alfalfa Plant Parts

Autotoxicity restricts reseeding of alfalfa (Medicago sativa L.) after alfalfa until autotoxic chemical(s) breaks down or is dispersed into external environments. A series of aqueous extracts from leaves, stems, roots and seeds of alfalfa ‘Vernal’ were bioassayed against alfalfa seedlings of the same cultivar to determine their autotoxicity. The highest inhibition was found in the extracts from the leaves. Extracts at 40 g dry tissue l^?1 from alfalfa leaves were 15.4, 17.5 and 28.7 times more toxic to alfalfa root growth than were those from roots, stems and seeds, respectively. A high‐performance liquid chromatography (HPLC) analysis with nine standard compounds showed that the concentrations and compositions of allelopathic compounds depended on the plant parts. In leaf extracts that showed the most inhibitory effect on root growth, the highest amounts of allelochemicals were detected. Among nine phenolic compounds assayed for their phytotoxicity on root growth of alfalfa, coumarin, trans‐cinnamic acid and o‐coumaric acid at 10^?3 m were most inhibitory. The type and amount of causative allelochemicals found in alfalfa plant parts were highly correlated with the results of the bioassay, indicating that the autotoxic effects of alfalfa plant parts significantly differed.     

Changes in Seed Yield and Quality with Maturity in Onion (Allium cepa L., cv. 'Early Cream Gold')

Development of onion (Allium cepa L., cv. ‘Early Cream Gold’) seed under cool climate conditions in Tasmania, Australia occurred over a longer duration than previously reported, but similar patterns of change in yield components were recorded. In contrast to previous studies, umbel moisture content declined from 85 to 67 % over 57 days while seed moisture content decreased from 85 to 31 %. Seed yield continued to increase over the duration of crop development, with increasing seed weight compensating for seed loss resulting from capsule dehiscence in the later stages of maturation. Germination percentage was high and did not vary significantly from 53 to 77 days after full bloom (DAF), but mean germination time declined and uniformity of germination increased significantly over the same time period. The percentage abnormal seedlings declined with later harvest date, resulting in highest seed quality at 77 DAF. The results of this study suggest that the decision to harvest cool climate onion seed crops before capsule dehiscence will result in a loss of potential seed yield and quality.     

Location of a high-lysine gene and the DDT-resistance gene on barley chromosome 7

Summary The high-lysine gene in Risø mutant 1508 conditions an increased lysine content in the endosperm via a changed protein composition, a decreased seed size, and several other characters of the seed. The designation lys3a, lys3b, and lys3c, is proposed for the allelic high-lysine genes in three Risø mutants, nos 1508, 18, and 19. Linkage studies with translocations locate the lys3 locus in the centromere region of chromosome 7. A linkage study involving the loci lys3 and ddt (resistance to DDT) together with the marker loci fs (fragile stem), s (short rachilla hairs), and r (smooth awn) show that the order of the five loci on chromosome 7 from the long to the short chromosome arm is r, s, fs, lys3, ddt. The distance from locus r to locus ddt is about 100 centimorgans.     

Simultaneous Determination of Four Phenolic Acids in Radix Salviae Miltiorrhizae Formula Granules by QAMS

[Objectives]This study aimed to establish a QAMS(quantitative analysis of multi-components by single-marker)method for simultaneous determination of four phenol...     

Water Extraction Process of Chinese Herbal Compound Man Gan Ning

[Objectives]To optimize the water extraction process of Chinese Herbal Compound Man Gan Ning and establish a method for its extraction and content determination...     

Present status and future strategy in breeding faba beans (Vicia Faba L.) for resistance to biotic and abiotic stresses

Progress is being made, mainly by ICARDA but also elsewhere, in breeding for resistance to Botrytis, AScochyta, Uromyces, and Orobanche; and some lines have resistance to more than one pathogen. The strategy is to extend multiple resistance but also to seek new and durable forms of resistance. Internationally coordinated programs are needed to maintain the momentum of this work.Tolerance of abiotic stresses leads to types suited to dry or cold environments rather than broad adaptability, but in this cross-pollinated species, the more hybrid vigor expressed by a cultivar, the more it is likely to tolerate various stresses.     

Pollen and pollination experiments. III. The viability of apple and pear pollen as affected by irradiation and storage

Summary Apple and pear pollen was irradiated with doses of 0, 50, 100, 250 and 500 krad (gamma rays) and stored at 4°C and 0–10% r.h. From the in-vitro germination percentages an average LD 50 dose of about 220 krad was estimated. For both irradiated and untreated pollen a close and corresponding lineair relationship existed between germination percentage and pollen tube growth.Irradiated pollen was much more sensitive to dry storage conditions than untreated pollen, resulting in less germination and more bursting. Apparently, irradiation caused the pollen cell membrane to lose its flexibility faster than normal. Rehydration of dry-stored, irradiated pollen in water-saturated air restored germination percentages up to their initial levels. The importance of this procedure in germination trials is stressed.     

Optimization of Extraction Technology and Determination of Content of Total Phenols of Leaves in Acanthopanax giraldii Harms

[Objectives] To determine the optimum extraction technology for total phenols of leaves in Acanthopanax giraldii Harms.[Methods]The single factor test and ortho...     

Cytoplasmic male sterility,resistance to gall mite and mildew,and season of leafing out in black currants

Summary Cytoplasmic male sterility (cms) is described in the F₁ hybrids Ribes × carrierei (R. glutinosum albidum × R. nigrum) and R. sanguineum × R. nigrum. In backcrosses to R. nigrum, progenies with R. glutinosum cytoplasm were either all male sterile, or segregated for full male fertility (F) and complete (S) and partial (I) male sterility. Ratios of F:I+S suggested that two linked genes controlled cms, F plants being dominant for one (Rf ₁) and recessive for the other (Rf ₂).Segregation for cms in relation to three linded genes, Ce (resistance to the gall mite, Cecidophyopsis ribes), Sph ₃(resistance to American gooseberry mildew, Sphaerotheca mors-uvae) and Lf ₁(one of two dominant additive genes controlling early season leafing out) indicated that Rf ₁and Rf ₂were in this linkage group. The gene order and approximate crossover values appeared to be: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqef0uAJj3BZ9Mz0bYu% H52CGmvzYLMzaerbd9wDYLwzYbItLDharqqr1ngBPrgifHhDYfgasa% acOqpw0xe9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% aabaqaciGacaGaamqadaabaeaafaaakeaacaWGdbGaamyzamaamaaa% baGaaiiiaiaacccacaGGWaGaaiOlaiaacgdacaGG0aGaaiiiaiaacc% caaaGaaiiiaiaacccacaGGGaGaamOuaiaadAgaliaaigdakmaamaaa% baGaaiiiaiaacccacaGGGaGaaiiiaiaaccdacaGGUaGaaiOmaiaacs% dacaGGGaGaaiiiaiaacccacaGGGaGaaiiiaaaacaWGsbGaamOzaSGa% aGOmaOWaaWaaaeaacaGGGaGaaiiiaiaacccacaGGGaGaaiiiaiaacc% cacaGGGaGaaiiiaiaacccaaaGaamitaiaadAgaliaaigdakmaamaaa% baGaaiiiaiaacccacaGGGaGaaiiiaiaacccacaGGGaGaaiiiaiaacc% cacaGGGaGaaiiiaiaacccacaGGGaaaaiaadofacaWGWbGaamiAaSGa% aG4maaaa!6E4D!\[Ce\underline { 0.14 } Rf1\underline { 0.24 } Rf2\underline { } Lf1\underline { } Sph3\]. Crossover values of 0.36 for Ce-Lf ₁, and 0.15 for Lf ₁-Sph ₃were estimated from the relative mean differences in season of leafing out between seedlings dominant and recessive for Ce and Sph ₃.It is suggested that competitive disadvantage of lf ₁-carrying gametes and/or zygotes at low temperatures may be implicated in the almost invariable deficit of plants dominant for the closely linked mildew resistance allele Sph ₃. Poor performance of lf ₁- (and possibly lf ₂-) carrying gametes and young zygotes during periods of low temperature at flowering might also account for the liability of some late season cultivars and selections to premature fruit drop (running off).     

Screening techniques and sources of resistance to parasitic angiosperms

Parasitic angiosperms cause great losses in many important crops under different climatic conditions and soil types. The most widespread and important parasitic angiosperms belong to the genera Orobanche, Striga, and Cuscuta. The most important economical hosts belong to the Poaceae, Asteraceae, Solanaceae, Cucurbitaceae, and Fabaceae. Although some resistant cultivars have been identified in several crops, great gaps exist in our knowledge of the parasites and the genetic basis of the resistance, as well as the availability of in vitro screening techniques. Screening techniques are based on reactions of the host root or foliage. In vitro or greenhouse screening methods based on the reaction of root and/or foliar tissues are usually superior to field screenings and can be used with many species. To utilize them in plant breeding, it is necessary to demonstrate a strong correlation between in vitro and field data. The correlation should be calculated for every environment in which selection is practiced. Using biochemical analysis as a screening technique has had limited success. The reason seems to be the complex host-parasite interactions which lead to germination, rhizotropism, infection, and growth of the parasite. Germination results from chemicals produced by the host. Resistance is only available in a small group of crops. Resistance has been found in cultivated, primitive and wild forms, depending on the specific host-parasite system. An additional problem is the existence of pathotypes in the parasites. Inheritance of host resistance is usually polygenic and its transfer is slow and tedious. Molecular techniques have yet to be used to locate resistance to parasitic angiosperms. While intensifying the search for genes that control resistance to specific parasitic angiosperms, the best strategy to screen for resistance is to improve the already existing in vitro or greenhouse screening techniques.