棉株体内几种生化物质与抗枯萎病之间关系的初步研究

 棉花抗枯萎病品种86-1、陕1155,感病品种岱15、徐州142。在棉幼苗三叶期用采自河南王屯的棉枯萎菌7号小种接种,接种后12小时,各抗病品种的葡萄糖、核糖含量显著增加,而感病品种则相反。接种后抗病品种的苯丙氨酸解氨酶(PAL)活性峰出现早于感病品种,相对酶活值也高于感病品种。接种后抗病品种蛋白质含量出现先低后高趋势,感病品种则始终保持较高水平。木质素含量的增加与棉花品种抗病性存在正相关性。伴随着PAL活性的增加,木质素含量也迅速增加。结果表明,棉花品种对枯萎病的抗性与PAL活性有密切关系,并通过代谢最终产物之一的木质素的增加得到表达。     

Effects of leaf wetness duration, relative humidity, light and dark on infection and sporulation by Didymella rabiei on chickpea

No infection occurred at less than 95% relative humidity (r.h.) when chickpea plants were dried after inoculation with conidia of Didymella rabiei. Infection was significant when the dry leaves were exposed to 98% r.h. for 48 h. When inoculated plants were subjected to different leaf wetness periods, some infection occurred with 4 h wetness, and disease severity increased with wetness duration according to an exponential asymptote, with a maximum value after about 18 h. Germination of conidia and germ tube penetration increased linearly with increasing wetness periods when recorded 42 h after inoculation. With a 24-h wetness period, germination of conidia was first observed 12 h after inoculation and increased linearly with time up to 52 h (end of the experiment). Dry periods immediately after inoculation, followed by 24-h leaf wetness, reduced disease severity; as the dry period increased the severity decreased. Disease severity increased with increasing periods of darkness after inoculation. The number of pycnidia and the production of conidia on infected leaves increased only slightly with high r.h. (either in the light or in the dark), but large increases occurred over an 8-day period when the leaves were kept wet.     

棉花黄萎病菌菌株间交互保护作用的研究(1)两菌株有效间隔天数的试验

 1983年和1984年,研究了棉株上接种黄萎病菌(Verticillium dahliae Kleb.)弱菌株对后继感染的强菌株所致病害的影响.接种弱菌株可减轻诱发的棉花黄萎病的病情.弱菌株与强菌株之间的接种间隔天数至关重要,以间隔5天接种,其交互保护作用最明显。     

Evaluation of resistance of Spanish olive cultivars to Verticillium dahliae in inoculations conducted in greenhouse

The resistance of 28 Spanish olive cultivars to Verticillium dahliae was evaluated in an experiment conducted under greenhouse conditions, by impregnating plant roots with a semisolid fluid mass of a mixture of culture medium and the conidia and mycelium of the fungus. Five-month-old olive plants were inoculated with a cotton defoliating isolate of V. dahliae. ‘Frantoio’ and ‘Picual’ were used as resistant and susceptible reference cultivars, respectively. Cultivars were assessed on the basis of final values of the area under the disease progress curve, mean severity of symptoms, and mortality at 26 weeks following inoculation. Verticillium wilt disease developed more slowly and reached lower values of these parameters than those normally recorded in previous studies conducted in growth chambers, using root-dip inoculation in a conidial suspension of the pathogen. However, most of the evaluated cultivars exhibited susceptible or moderately susceptible reactions to the infections caused by V. dahliae. In particular, a group of eight cultivars, from the same group as ‘Picual’, such as ‘Manzanilla de Abla’, ‘Manzanilla del Centro’ and ‘Negrillo de Iznalloz’, were significantly more susceptible than ‘Frantoio’. Conversely, ‘Escarabajillo’, ‘Menya’ and ‘Sevillana de Abla’ exhibited a high level of resistance to the disease, no dead plants, and vegetative recovery. Field experiments are currently being carried out to confirm the level of resistance assigned to these last genotypes. If confirmed, these genotypes will act as potential resistant genitors for inclusion in current olive breeding programs or for use as resistant rootstocks.     

Present status of bacterial blight in cotton genotypes evaluated at Busia and Siaya counties of Western Kenya

Bacterial blight (BB) incited by Xanthomonas citri subsp. malvacearum (Xcm) is an important bacterial disease occurring in all cotton growing areas throughout the world, including parts of Western Kenya, that are characterized by a hot and humid climate. The disease causes seedling blight, angular leaf spot, boll rot and black arm on petioles and branches leading to a loss of fruiting branches with yield losses of up to 35 %. Fifty- one Kenyan cotton genotypes (Gossypium hirsutum L.) were established in the two counties of Siaya and Busia famous for their cotton cultivation in the western region. The BB symptoms caused by natural Xcm infection in the field were scored for each cotton accession. In addition artificial inoculation with the same strains was done to confirm the status under controlled greenhouse conditions. The results of BB disease scoring revealed that some accessions (e.g. T 24A and T 24B) possess a reasonable level of resistance. However, most of the Kenyan genotypes surveyed showed medium to severe symptoms of BB, including KSA 81 M, the only commercially grown cultivar in the region of Western Kenya. Overall, 71 % of the genotypes showed susceptibility and 29 % were classified as either resistant or moderately resistant. There is therefore need to improve the local commercial genotypes by introducing new genetic resources with a more durable BB resistance to ensure a successful revitalization of the Kenyan cotton sector.     

Early development of light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape (Brassica napus) in relation to temperature and leaf wetness.

In controlled environment experiments to study early development of light leaf spot, lesions developed with leaf wetness durations of 16 to 48 h after inoculation of oilseed rape with conidial suspensions of Pyrenopeziza brassicae at 12 or 18°C, but not with leaf wetness durations of 0 to 13h. The incubation period was 21 to 22 days at 12°C and 14 to 18 days at 18°C for leaf wetness durations of 16 to 48 h. The latent period was 21 to 23 days at 12°C and 18 to 19 days at 18°C, and the total number of lesions increased with increasing leaf wetness duration at both temperatures. In field experiments, light leaf spot always developed on oilseed rape with a leaf wetness duration of 48 h after inoculation in both 1990/1991 and 1991/1992, but the percentage leaf area affected was less on plants placed in an oilseed rape crop than on those placed in a glasshouse. Plants moved to an oilseed rape crop immediately after inoculation nearly always developed light leaf spot symptoms when they were inoculated between 19 October 1990 and 1 March 1991 or between 27 September 1991 and 14 February 1992, but plants inoculated between 31 August and 16 October 1990 or on 20 September 1991, when estimated leaf wetness duration was less than 16 h for several days after they were placed in crops, did not develop symptoms. The latent period of light leaf spot on plants transferred to the oilseed rape crop was 15 to 40 days, and there was an approximately linear relationship between 1 (latent period) and mean temperature during this period. The accumulated temperature during the latent period ranged from c. 150 to 250 day-degrees. The severity of lesions on these plants increased with increasing temperature from 5 to 15°C.     

Systemic infection of sorghum and corn by conidia ofSclerospora Sorghi

Conidia ofSclerospora sorghi, obtained from either systemically-infected or local-lesion-infected leaves of sorghum (cv. Vidan), were capable of inducing typical downy mildew systemic infection, including oospore formation, in sorghum and corn hybrids. Very young inoculated seedlings displayed chlorotic systemic symptoms already on the first leaf, and often died at fourth-leaf stage. Systemic infection was induced by conidia on sorghum 1–14 days old at inoculation. Incidence of infection was much higher and symptoms less delayed when the shoot rather than coleorhizas of young sorghum and corn seedlings were inoculated; in two-week-old sorghum with three leaves, inoculation of the coleoptile or of the base of the second and third blades resulted in systemic infection; with coleoptile inoculation partial leaf chlorosis was delayed until the fourth-or fifth-leaf stage, showing that penetration without symptoms had occurred as far as the meristematic tissues of young leaves still within the leaf tube. Conidial inoculation of young sorghum tillers sprouting after cutting down healthy mother shoots resulted in systemic infection. Conidial inoculum is deemed to be the probable major means for systemic infection of corn and sorghum sown in fields in which oospores are not present; inoculation of new tillers of forage sorghum by conidia from infected plants in a neighboring field can explain the rise in numbers of plants systemically stricken. Two sweet corn hybrids — one considered resistant in the field, the other very susceptible — proved equally susceptible when inoculated with conidia at 5 days of age.     

Efficacy of Hypovirulent Binucleate Rhizoctonia sp. to Control Banded Leaf and Sheath Blight in Corn

Water agar, artificially infested soil and leaf sheath inoculation methods were used to assess the suitable time of application, varietal host response and persistence of Rhv7, a hypovirulent, binucleate Rhizoctonia collected from soil in the Philippines, to effectively control virulent Rhizoctonia solani AG1-IA isolate RS35 on corn. With the water agar method, prior inoculation (2 to 3 days) with the biocontrol agent is essential to achieve maximum control of the pathogen. Disease protection was increased from 23 to 70% as the pre-incubation time of Rhv7 prior to the challenge inoculation with virulent isolate was lengthened from 0 to 3 days. Disease severity and incidence of banded leaf and sheath blight (BLSB) on the three corn hybrids were also suppressed in artificially infested soil. In leaf sheath inoculation, the suppressive ability of Rhv7 against BLSB on corn persisted during lesion expansion. This suppression was expressed as slower disease progress in plants with Rhv7 than in plants without Rhv7. Early and timely brace root formation that detached infected sheaths, also aided in reducing the number of diseased plants in Rhv7-treated plots at the final observation. Mycelial growth activity of RS35 was reduced when corn plants were pre-inoculated with Rhv7 before challenge even if there was no contact detected between Rhv7 and RS35, which suggests that Rhv7 protects corn against BLSB by induced resistance. The hypovirulent, binucleate Rhizoctonia Rhv7 strain effectively controlled R. solani AG1-IA isolate RS-35 in corn. Received 30 August 1990/ Accepted in revised form 25 October 1999     

A green fluorescent protein-based screening method for identification of resistance in anthurium to systemic infection by Xanthomonas axonopodis pv. dieffenbachiae

Resistance of cultivars of Anthurium andraeanum to systemic infection by Xanthomonas axonopodis pv. dieffenbachiae , the causal organism of bacterial blight disease of anthurium, was investigated using a bioengineered bacterial strain containing p519ngfp plasmid. Successful infection establishment in anthurium was found to be cultivar and inoculum density dependent, but independent of plant age. Injection of cut petioles (stage-2 leaf) with 100  µ L inoculum (10⁹ CFU mL⁻¹) resulted in 100% infection establishment in susceptible cultivars on a repeatable basis, and differentiated between various levels of observed field resistance. Time to death (weeks) and proportion of dead plants best differentiated between levels of resistance and cultivars were placed in four groups based on these criteria. The susceptible group (32 cultivars) rapidly declined within 6–12 weeks of inoculation (WAI) and resulted in 100% plant death; the moderately resistant group (10 cultivars) declined within 12 WAI, but resulted in less than 100% plant death; the resistant category had less than 100% plant death with a slow decline taking over 20 weeks; and the highly resistant category (15 cultivars) showed 0% infection. The correlation coefficient between green fluorescent protein (GFP)-fluorescence and eventual death of plants was 0·90, indicating that the final death of individual plants can be reasonably well predicted based on GFP-fluorescence data at 5 WAI. Hence GFP data at 5 WAI can be used for early detection of latently infected plants and may assist screening for resistance in segregating populations of anthurium.     

棉叶螨危害对棉花生理和产量的影响

棉叶螨危害致使棉花生理和代谢发生紊乱是造成棉花减产的内在原因。1984—1985年,作者采用人工接螨和控制螨量的方法,任其自然繁殖28天,使各处理株间出现螨量和被害指数梯度,然后测定各处理株主要生理参数及其产量。结果表明,当全株每叶初接螨量在5头以上、螨群最高繁殖量高于35头时,处理株比对照株组织水势增高13.11—34.31％;叶绿素含量减少39.60—62.50％;光合强度减弱23.47—89.29％;过氧化氢酶活性降低22.79—48.04％;呼吸强度变化差异不显著。棉叶中可溶性糖、全氮、全磷损失显著,营养恶化。单株籽棉重降低35.18—45.10％,平均铃重降低24.34—35.53％。据此,确定棉叶螨防治标准为全株平均每叶螨量20头。     

A greenhouse screening technique to assess rust resistance in sorghum∗

Abstract

Studies were conducted to determine the influence of plant growth stage, inoculum density, temperature, and relative humidity (RH) on development of rust (Puccinia pupurea) in sorghum (Sorghum bicolor). Rust development was maximum (>80% severity), when plants of a susceptible sorghum genotype (IS 18420) were inoculated at the four‐ to five‐leaf stage with an inoculum concentration of 4 × 10⁶ urediniospores per ml and incubated at 20–25°C under high RH (>90%) for 24 h. Disease severity (percentage leaf area covered with rust pustules) scores were taken 2 weeks after inoculation. Using this technique, 29 sorghum genotypes were screened for rust resistance in a greenhouse. This technique proved effective In discerning resistant and susceptible genotypes, and IS 3979, ICSH 110, ICSH 86647 and ICSH 871035 were identified resistant (<20% rust severity) compared with a susceptible control IS 18420 (90% rust severity). This technique is simple and rapid, and can be used effectively and economically to screen, on a large scale, germplasm lines and breeding populations in the greenhouse.     

Is the accumulation of a systemic fungicide at the infection site related to its eradicative action?

Restricted areas of Avena sativa leaves were infected with Puccinia coronata. The systemic fungicide [³H]triarimol was later applied to the roots of these plants. The fungicide did accumulate at the infection sites when applied 14 days after inoculation, but not when applied 4 or 9 days after inoculation. It is concluded that the accumulation of the fungicide at the infection zone is a result of enhanced evaporation from leaf tissues (probably) because the epidermis was broken after pustule formation.     

Interactions in the Brassica napus–Pyrenopeziza brassicae pathosystem and sources of resistance to P. brassicae (light leaf spot)

Pyrenopeziza brassicae, cause of light leaf spot (LLS), is an important pathogen of oilseed rape and vegetable brassicas and has a wide geographic distribution. Exploitation of host resistance remains the most sustainable and economically viable solution for disease management. This study evaluated 18 oilseed rape cultivars or breeding lines for host resistance against P. brassicae in glasshouse experiments. Selected cultivars/lines were inoculated with eight single-spore isolates of the pathogen obtained from three different regions in England. Analysis of P. brassicae infection-related changes on host plants identified leaf deformation as a characteristic feature associated with P. brassicae infection, this showed poor correlation to LLS severity measured as the amount of pathogen sporulation on infected plants. Resistant host phenotypes were identified by limitation of P. brassicae sporulation, with or without the presence of a necrotic response (black flecking phenotype). Investigation of this pathosystem revealed significant differences between cultivars/lines, between isolates, and significant cultivar/line-by-isolate interactions. In total, 37 resistant and 16 moderately resistant interactions were identified from 144 cultivar/line-by-isolate interactions using statistical methods. Most of the resistant/moderately resistant interactions identified in this study appeared to be nonspecific towards the isolates tested. Our results suggested the presence of isolate-specific resistant interactions for some cultivars. Several sources of resistance have been identified that are valuable for oilseed rape breeding programmes.     

棉田黄顶菊的经济阈值及竞争临界期

黄顶菊是近年在我国发现的外来入侵植物,在河北省已进入农田.为明确黄项菊在棉田中的经济危害允许水平、经济阈值以及竞争临界期,采用添加系列试验和模型拟合的方法,在田间条件下研究黄顶菊不同密度对棉花的生长性状及产量的影响.结果表明,在黄顶菊的竞争干扰下,棉花的叶面积指数、田间透光率、水分利用效率、氮素利用效率和棉花产量均随黄顶菊密度的增加而逐渐降低.当黄顶菊密度为5株/m~2时,叶面积指数、田间透光率、水分利用效率和氮素利用效率显著低于无黄顸菊对照;当密度为2株/m~2时,棉花产量显著低于无黄顶菊对照.对数函数模型可以较好地拟合黄顶菊密度与棉花产量损失间的关系(γ=22.79 lnx十9.0277,R=0.9759).棉田中黄顶菊的经济危害允许水平为0.66%～3.06%,经济阈值为0.69～0.77株/m~2,与棉花的竞争临界期为棉花播种后5.15～83.13天.     

棉花枯萎病菌的致病性及其碳素营养的试验研究

南通棉花枯萎病菌对22个棉花品种致病性的田間和盆栽試驗说明:中棉品种如辽阳一号、鶯湖棉、长丰黑籽、常紫一号、南通白花鸡脚桠鈴果、云南布沼土棉等抗病性比較強,以中棉为母本的中印杂交棉的抗病性也較強;陆地棉和海島棉一般感病程度都較高,但四川选育的陆地棉品种52—128則具有一定的抗病性。将枯萎病菌接种到甘藷等27种作物上,均未感病。五个地区的棉花枯萎病菌致病性的盆栽試驗说明:四川、陝西、辽宁的病原菌致病力較強,江苏的其次,安徽的最弱。以葡萄糖、果糖、半乳糖、甘露糖、乳糖、蔗糖、菊糖、溶解淀粉、阿拉伯糖醇等九种糖和糖醇为碳素营养料时,除四川的病原菌在以半乳糖为碳素营养料时生长中等外,其他都生长旺盛。不同地区病原菌的色素形成、小型孢子、大型孢子和厚膜孢子的产生,随碳素营养料的不同而有所差異。     

Host–pathogen interaction between Phytophthora infestans and Solanum nigrum, S. villosum, and S. scabrum

Potato and tomato are the two major hosts for Phytophthora infestans causing late blight. The susceptibility of leaves and whole plants of Solanum nigrum, S. villosum, and S. scabrum to infection by P. infestans was tested under laboratory conditions. Out of 39 plants representing 38 different S. nigrum accessions, 16 were highly resistant (seven accessions did not show any symptoms of infection, nine were highly resistant showing necrotic lesions in the place of infection), and 23 plants of S. nigrum were colonized by, at least, 1 of the 2 isolates of P. infestans (17 accessions were infected with two P. infestans isolates, and 6 accessions showed different reactions depending on the isolate used for inoculation). Three accessions of S. villosum, and one accession of S. scabrum were tested and did not show any symptoms of infection. The majority of S. nigrum accessions infected by P. infestans in a detached leaf assay were also infected in the whole plant assay. The reaction of field- and greenhouse-grown plants to inoculation with P. infestans in detached leaf assays was similar, but in some cases leaves from field-grown plants reacted as resistant in comparison with the leaves from greenhouse-grown plants, which were susceptible.     

山东省玉米生产品种和部分自交系对纹枯病抗性鉴定

连续两年对山东省72份玉米生产品种和30份自交系材料在田间进行纹枯病抗性鉴定,采用被病原菌侵染的高粱粒作为接种物,在玉米拔节中后期接种,按照国家玉米区域试验抗性鉴定标准进行病害分级评定和抗性评价。在102份材料中抗性级别为高抗、抗、中抗、感、高感的比例分别为1.96%、20.59%、24.51%、33.33%、19.61%,生产品种‘登海3号’和‘聊玉22号’对纹枯病表现高抗。     

Genetics of resistance to cotton leaf curl disease in Gossypium hirsutum

Twenty-two cotton varieties were screened for resistance to cotton leaf curl disease (CLCuD), a disease of viral origin, using three procedures: field evaluation, whitefly transmission assay and graft inoculation. Viral infection of cotton varieties was determined by visual symptom assessment as well as dot-blot and multiplex PCR diagnostic techniques. Crosses were made between the most susceptible variety (S-12) and highly resistant varieties (CP-15/2, LRA-5166 and CIM-443). All F₁ plants of these crosses were resistant, showing dominant expression of the resistance as well as the absence of extrachromosomal inheritance. The F₂ plants of the crosses CP-15/2 × S12, LRA-5166 × S-12 and CIM-443 × S12 exhibited a ratio of 13 resistant (symptomless) to three susceptible (with symptoms). Screening of the F₂ generation for virus infection by multiplex PCR further subdivided the resistant class into those exhibiting a high level of resistance (HR; PCR-negative) and those exhibiting resistance (R; symptomless, yet showing virus replication by PCR analysis). Hence, the final ratio was 3:10:3 (HR:resistant:susceptible). The F₃ progeny of susceptible F₂ plants segregated for resistance, indicating the probable presence of a suppressor gene ( S ). These findings are consistent with three genes being involved in G. hirsutum resistance to CLCuD, two for resistance ( R _1CLCuDhir and R _2CLCuDhir ) and a suppressor of resistance ( S _CLCuDhir ).     

三大棉种对棉花主要病害抗性研究

1633个陆地棉、海岛棉、中棉三大棉种的品种资源和42个生产上推广应用的陆地棉品种,在田间病圃和温室接菌,进行对枯萎病、黄萎病、苗病、铃病的抗病性鉴定。结果表明,中棉对枯萎病、苗病,铃病均有较高的抗病能力,但对黄萎病抗性较差;海岛棉对黄萎病有很高的抗病能力,但对枯萎病、苗病、铃病抗性均较差;陆地棉对棉花4种主要病害的抗病性能高于海岛棉,但低于中棉。经生物统计分析,仅发现陆地棉抗枯萎病与抗苗病之间存在显著的正相关关系。推荐中棉12、陕1155、86-2、86-3、冀合3016五个兼抗枯、黄萎病,并对苗病、铃病也有一定耐病性的品种,供各地多抗育种选用。     

Silicon suppresses tan spot development on wheat infected by <Emphasis Type="BoldItalic">Pyrenophora tritici-repentis</Emphasis>

Tan spot caused by Pyrenophora tritici-repentis is the main foliar diseases of wheat in Brazil. The effect of silicon (Si) on the components of resistance of a susceptible (Fundacep Horizonte) and a moderately resistant (Quartzo) wheat cultivar was studied in a controlled environment. Silicon was supplied as calcium silicate in the soil 30 days before sowing. At the booting stage, a conidial suspension of the fungus was sprayed onto the flag leaves of potted plants, which were incubated under moist conditions for 48 h. Afterwards, inoculated leaves were assessed for: incubation period (IP), infection efficiency (IE), area under lesion size curve (AULSC), lesion size (LS), severity (SEV) and area under severity curve (AUSC). Foliar Si concentrations were quantified at the end of the evaluations. Si supply to plants increased leaf Si concentration in 233% for Fundacep Horizonte (from 4.8 to 16.0 g kg^?1 of dry matter) and 211% for Quartzo (from 5.3 to 16.5 g kg^?1 of dry matter). In the Si + treatments, IP was longer by 24 and 17 h, IE declined by 53.5 and 65.5%, LS (at 264 h after inoculation) by 4.6 mm (from 9.5 to 4.9 mm) and 5.9 mm (from 8.2 to 2.3 mm), and SEV by 53% (from 54.4 to 18.8%) and 88% (from 47.7 to 5.5%) respectively, for the Fundacep Horizonte and Quartzo cultivars. The Si x cultivar interaction was not significant for AULSC and AUSC, and these variables were reduced by 55.8 and 80.8%, respectively, in plants supplied with Si. In conclusion, Si enhanced the resistance of wheat plants to tan spot development by affecting several resistance components, regardless of the resistance level of the cultivar. However, the greatest reduction in tan spot development by Si supply was observed when using a moderately resistant cultivar.