Effects of Angular Leaf Spot and Rust on Yield Loss of Phaseolus vulgaris

ABSTRACT Three field experiments were conducted in 1997, 1998, and 1999 to investigate the effects of angular leaf spot and rust, separately or combined, on host growth and yield of individual bean plants (Phaseolus vulgaris). In each experiment, three treatments were established by inoculating cv. Carioca with Phaeoisariopsis griseola, Uromyces appendiculatus, or with both pathogens. An additional control treatment was not inoculated, but was sprayed with a fungicide. In the 1997 and 1999 experiments, angular leaf spot reached higher disease levels than rust, whereas in 1998, rust was more severe than angular leaf spot. Host growth, expressed as healthy leaf area duration (HAD), and yield were the highest in 1997 and lowest in 1998. In each experiment, the treatments did not differ significantly to the area under leaf area progress curve, HAD, and healthy leaf area absorption (HAA). All inoculated treatments had significantly more severe disease and less yield than the control treatment. Based on the analysis of 60 plants in each experiment, yield was not related to the areas under disease progress curve for either or both diseases. In 1997 and 1999, yield was related to HAD (R(2) = 0.57 and 0.43) and HAA(R(2) = 0.60 and 0.55). Based on the combined analysis of all 36 plots, angular leaf spot reduced the leaf area because of defoliation, whereas rust did not affect the leaf area. Rust reduced yield more than four times that of angular leaf spot, although the decrease in photosynthesis to angular leaf spot was twice that of rust.     

乌鲁木齐气象要素对大气气溶胶光学特性的影响

利用2002年4月～2003年3月CE 318太阳光度计和同期气象观测资料,分析不同气象条件下,乌鲁木齐气溶胶光学厚度的变化.结果表明:在冬季高湿的条件下,各时次相对湿度和AOD的相关系数较高,为0.335.春夏季比较干燥时,相对湿度的影响不大;风速和AOD的变化趋势总体呈现负相关关系,即风速越大,AOD则越小,在发生东南大风或山谷风时,这种趋势更为明显;全年中偏北风和偏南风对乌鲁木齐气溶胶光学厚度的贡献较大.     

Effects of Environmental Factors on Development of Pyrenopeziza brassicae (Light Leaf Spot) Apothecia on Oilseed Rape Debris

ABSTRACT The development of Pyrenopeziza brassicae (light leaf spot) apothecia was studied on petiole debris from artificially infected oilseed rape leaves incubated at temperatures from 6 to 22 degrees C under different wetness regimes and in 16 h light/8 h dark or continuous darkness. There was no significant difference between light treatments in numbers of apothecia that developed. Mature apothecia developed at temperatures from 5 to 18 degrees C but not at 22 degrees C. The rate of apothecial development decreased as temperature decreased from 18 to 5 degrees C; mature apothecia were first observed after 5 days at 18 degrees C and after 15 days at 6 degrees C. Models were fitted to estimates of the time (days) for 50% of the maximum number of apothecia to develop (t(1); model 1, t(1) = 7.6 + 55.8(0.839)(T)) and the time for 50% of the maximum number of apothecia to decay (t(2); model 2, t(2) = 24.2 + 387(0.730)(T)) at temperatures (T) from 6 to 18 degrees C. An interruption in wetness of the petiole debris for 4 days after 4, 7, or 10 days of wetness delayed the time to observation of the first mature apothecia for approximately 4 days and decreased the number of apothecia produced (by comparison with continuous wetness). A relationship was found between water content of pod debris and electrical resistance measured by a debris-wetness sensor. The differences between values of t(1) predicted by model 1 and observed values of t(1) were 1 to 9 days. Model 2 did not predict t(2); apothecia decayed more quickly under natural conditions than predicted by model 2.     

赭红枝顶Acremoniumsalmoneum对竹叶锈病菌的重寄生作用研究

竹叶锈病（Pucciniaspp．）是竹类主要病害之一,影响竹林生长。为了利用重寄生菌赭红枝顶孢Acremoniumsalmoneum防治竹叶锈病,本文研究了该重寄生菌的寄生规律及其抑病作用。结果表明,该重寄生菌的分生孢子自然条件下可在锈病病斑上越冬,作为次年重寄生的初侵染源;分生孢子主要依靠风吹雨溅在林间传播,可发生多次再侵染;林间温度在16．4～25．4℃下,潜育期为10～18d;采用纸环法观察重寄生菌对锈病菌（Puccinialongicornis和尸phyllostachydis）夏孢子的萌发情况可知,重寄生菌对锈病菌夏孢子的萌发有较强的抑制作用,24h后2种锈菌夏孢子的萌发率均很低,分别仅为11．1％和8．7％,同时该重寄生菌可抑制锈病病斑的扩展。竹叶锈病重寄生发生与环境条件有密切关系,在竹林较密、经营管理较差的林分竹叶锈病重寄生率明显较高。     

Observations on the Development of Groundnut Rust in Australia

Abstract

Groundnut rust was recorded from the Adelaide River district, Northern Territory and the Atherton Tableland, Queensland in April 1973. Wind-borne uredospores from the north are suspected as the primary inoculum. The disease was found in crops near the Ord River, Western Australia in June 1973 and in the main producing area near Kingaroy, Queensland in February 1976. Seasonal carry-over is achieved on self-sown plants. Economic loss has occurred in the tropical districts where fungicidal spraying for rust control is now practised.     

Wheat Leaf Rust Uredospore Production on Adult Plants: Influence of Leaf Nitrogen Content and Septoria tritici Blotch

ABSTRACT Leaf rust uredospore production and lesion size were measured on flag leaves of adult wheat plants in a glasshouse for different lesion densities. We estimated the spore weight produced per square centimeter of infected leaf, per lesion, and per unit of sporulating area. Three levels of fertilization were applied to the plants to obtain different nitrogen content for the inoculated leaves. In a fourth treatment, we evaluated the effect of Septoria tritici blotch on leaf rust uredospore production. The nitrogen and carbon content of the spores was unaffected or marginally affected by lesion density, host leaf nitrogen content, or the presence of Mycosphaerella graminicola on the same leaf. In leaves with a low-nitrogen content, spore production per lesion was reduced, but lesion size was unaffected. A threshold effect of leaf nitrogen content in spore production was however, evident, since production was similar in the medium- and high-fertilizer treatments. In leaves inoculated with M. graminicola and Puccinia triticina, the rust lesions were smaller and produced fewer spores. The relationships among rust lesion density, lesion size, and uredospore production were fitted to a model. We determined that the density effect on spore production resulted mainly from a reduction in lesion size, the spore production per unit of sporulating surface being largely independent of lesion density. These results are consistent with those obtained previously on wheat seedlings. The main difference was that the sporulation period lasted longer in adult leaves.     

Evaluation of Wheat Leaf Rust Resistance Genes in 10 Wheat Genotypes

Journal of Plant Diseases and Protection - Wheat leaf rust (Puccinia triticina) is one of the most important plant diseases in the world, and growing resistant cultivars is the most economical,...     

Leaf Rust on Aegilops speltoides Caused by a New Forma Specialis of Puccinia triticina

ABSTRACT A leaf rust attacking Aegilops speltoides in its natural habitat is reported for the first time. It was found in two locations in northern and central Israel. The two collections from A. speltoides resemble wheat leaf rust, Puccinia triticina, in most spore dimensions, in the morphology of the substomatal vesicle of the urediniospore, and in DNA content in pycniospore nuclei. Similarly to P. triticina isolates from wheat, isolates taken from A. speltoides are compatible with Thalictrum speciosissimum as an aecial host and they are crossed easily with wheat leaf rust isolates. However, isolates from A. speltoides differ from wheat leaf rust in their telial host range. They are avirulent to cultivated wheat cultivars, but attack hundreds of A. speltoides accessions that were immune to wheat leaf rust. This distinct host preference justifies delineation of the newly found leaf rust as a forma specialis (f. sp. speltoides) within P. triticina.     

Characterization of a New Subgroup of Rhizoctonia solani Anastomosis Group 1 (AG-1-ID), Causal Agent of a Necrotic Leaf Spot on Coffee

ABSTRACT A new foliar disease on coffee leaves was observed in Mindanao, Philippines, in 1996. The symptoms appeared as large circular or irregularly shaped necrotic areas with small circular necrotic spots (1 mm or less in diameter) usually found around the periphery of the large necrotic areas. Rhizoctonia solani was consistently isolated from these diseased coffee leaves. Isolates obtained were multinucleate (3 to 12 nuclei per hyphal cell), had an optimum temperature for hyphal growth at 25 degrees C, prototrophic for thiamine, and anastomosed with tester isolates belonging to R. solani anastomosis group 1 (AG-1). Mature cultures on potato dextrose agar (PDA) were light to dark brown. Sclerotia, light brown to brown, were formed on the surface of PDA and covered the whole mature colony culture. Individual sclerotia often aggregated into large clumps (3 to 8 mm in diameter) and their color was brown to dark brown. In pathogenicity tests, isolates from coffee caused necrotic symptoms on coffee leaves, whereas isolates of AG-1-IA (not isolated from coffee), 1-IB, and 1-IC did not. The results of analyses of restriction fragment length polymorphism of ribosomal DNA internal transcribed spacer, random amplified polymorphism DNA, and fatty acid profiles showed that R. solani isolates from coffee are a population of AG-1 different from AG-1-IA, 1-IB, and 1-IC. These results suggest that R. solani isolates from coffee represent a new subgroup distinct from AG-1-IA, 1-IB, and 1-IC. A new subgroup ID (AG-1-ID) is proposed.     

Virulence and Molecular Polymorphism in International Collections of the Wheat Leaf Rust Fungus Puccinia triticina

ABSTRACT Collections of Puccinia triticina, the wheat leaf rust fungus, were obtained from Great Britain, Slovakia, Israel, Germany, Australia, Italy, Spain, Hungary, South Africa, Uruguay, New Zealand, Brazil, Pakistan, Nepal, and eastern and western Canada. All single-uredinial isolates derived from the collections were tested for virulence polymorphism on 22 Thatcher wheat lines that are near-isogenic for leaf rust resistance genes. Based on virulence phenotype, selected isolates were also tested for randomly amplified polymorphic DNA (RAPD) using 11 primers. The national collections were placed into 11 groups based on previously established epidemiological zones. Among the 131 single-uredinial isolates, 105 virulence phenotypes and 82 RAPD phenotypes were described. In a modified analysis of variance, 26% of the virulence variation was due to differences in isolates between groups, with the remainder attributable to differences within groups. Of the RAPD variation, 36% was due to differences in isolates between groups. Clustering based on the average virulence distance (simple distance coefficient) within and between groups resulted in eight groups that differed significantly. Collections from Australia-New Zealand, Spain, Italy, and Britain did not differ significantly for virulence. Clustering of RAPD marker differences (1 - Dice coefficient) distinguished nine groups that differed significantly. Collections from Spain and Italy did not differ significantly for RAPD variation, neither did collections from western Canada and South America. Groups of isolates distinguished by avirulent/virulent infection types to wheat lines with resistance genes Lr1, Lr2a, Lr2c, and Lr3 also differed significantly for RAPD distance, showing a general relationship between virulence and RAPD phenotype. The results indicated that on a worldwide level collections of P. triticina differ for virulence and molecular backgrounds.     

Effects of Brown Rust caused by Puccinia recondita on Wheat

Abstract

Plants of susceptible and resistant varieties were inoculated with the brown rust pathogen Puccinia recondita. Rust reduced the average plant height, weight of grain, volume of grain and yield of susceptible varieties compared with healthy controls. Two varieties, Lerma Rojo and E.871 were resistant and are recommended for use in further hybridisation work.     

Effects of leaf blast on photosynthesis of rice. 1. Leaf photosynthesis

The effect ofPyricularia oryzae, the causal organism of leaf blast in rice, on photosynthesis characteristics of rice leaves was measured in two greenhouse experiments. Leaf blast reduced photosynthesis not only through a reduction in green leaf area, but also through an effect on photosynthesis of green leaf tissue surrounding the lesions. The assimilation rate at light saturation (P _max ) was more affected than the initial light use efficiency (). Dark respiration (R _d ) increased as a result of infection. The experimental data were used to derive relations between leaf blast severity andP _max , andR _d .     

锡林郭勒盟春季沙尘暴成因的气象因子分析

本文选取了锡林郭勒地区沙尘暴高发季节春季(3~5月)的大风日数、气温、相对湿度等气象因子,通过对当地气象因子的调查,采用基于因子分析的主成分提取方法,将气象因子分为3个主成分,并分析了各主成分的意义,通过对沙尘暴成因的各种气象因素所作的定量和定性分析,在沙尘暴的预报和监测中具有重要的实际意义。     

Use of Meteorological Information for Forecasts of Pest Development based on Models and Computers1

A computerized simulation model for the development of Leptinotarsa decemlineata is described. The model uses biological and meteorological data as input, and outputs the ecological reproduction coefficient. Calculated values correlate satisfactorily with observed reproduction coefficients. The model has been used to forecast these coefficients for average conditions in five zones in the USSR, and in 12 other European countries.     

论气象灾害对新疆国民经济的影响及其对策

本文用了大量的资料论证了气象灾害是新疆主要的自然灾害，同时，阐明了气象灾害是制约新疆国民经济发展的一大因素，以及产生原因及其对策。     

主要栽培因子对稻纹枯病病情进展的影响

本文研究了主要栽培因子（品种、氮肥、钾肥和植株密度等）对早稻纹枯病的影响。结果表明：纹枯病的发展随施氮量的增加而加重，其敏感点为纯氮７．５～１２．５ｋｇ／６６７ｍ２；品种间抗感差异明显，其感病程度可分为３类，浙辐８０２和先锋一号发病轻为Ⅰ类；二九丰和湘早籼３号为Ⅱ类；二九青和双矮早发病较重为Ⅲ类。品种与施氮量互作效应对病情发展影响显著；氮、钾肥和植株密度对纹枯病进展速率的影响是氮肥＞植株密度＞钾肥。其交互作用明显的是氮肥和钾肥的互作。     

The Effects of Benomyl on the Growth and Development of Wheat1

Wheat crops treated with benzimidazole-containing fungicides have often shown small increases in yield in the absence of any detectable disease. This project was designed to test the possibility that direct physiological effects of the fungicide were responsible. The major effect of benomyl, at concentrations in the range 200–5000 ppm was to increase the development of tillers. Spraying at any one of several stages of development caused an increase in the number of tillers detected about 6 weeks later. This was found to be due to a more rapid initiation of tillers and not to more rapid growth following initiation. Associated with this earlier initiation was an increase in the incorporation of C14-labelled assimilates into newly initiated tiller buds, but not into older ones. These responses resemble those reported for the effects of cytokinin applications to cereals. In field experiments, the increase in tiller production caused an increase in ear number only when plants were widely spaced. The decrease in tiller number as plant density increased was more rapid in treated plants than in controls, so that both treatments produced similar ear densities at around optimum plant density.     

Performance and Mapping of Leaf Rust Resistance Transferred to Wheat from Triticum timopheevii subsp. armeniacum

ABSTRACT Host plant resistance is an economical and environmentally sound method of control of leaf rust caused by the fungus Puccinia triticina, which is one of the most serious diseases of wheat (Triticum aestivum) worldwide. Wild relatives of wheat, including the tetraploid T. timopheevii subsp. armeniacum, represent an important source of genes for resistance to leaf rust. The objectives of this study were to (i) evaluate the performance of leaf rust resistance genes previously transferred to wheat from three accessions of T. timopheevii subsp. armeniacum, (ii) determine inheritance and allelic relationship of the new leaf rust resistance genes, and (iii) determine the genetic map location of one of the T. timopheevii subsp. armeniacum-derived genes using microsatellite markers. The leaf rust resistance gene transferred to hexaploid wheat from accession TA 28 of T. timopheevii subsp. armeniacum exhibited slightly different infection types (ITs) to diverse races of leaf rust in inoculated tests of seedlings compared with the gene transferred from TA 870 and TA 874. High ITs were exhibited when seedlings of all the germ plasm lines were inoculated with P. triticina races MBRL and PNMQ. However, low ITs were observed on adult plants of all lines having the T. timopheevii subsp. armeniacum-derived genes for resistance in the field at locations in Kansas and Texas. Analysis of crosses between resistant germ plasm lines showed that accessions TA 870 and TA 874 donated the same gene for resistance to leaf rust and TA 28 donated an independent resistance gene. The gene donated to germ plasm line KS96WGRC36 from TA 870 of T. timopheevii subsp. armeniacum was linked to microsatellite markers Xgwm382 (6.7 cM) and Xgdm87 (9.4 cM) on wheat chromosome arm 2B long. This new leaf rust resistance gene is designated Lr50. It is the first named gene for leaf rust resistance transferred from wild timopheevi wheat and is the only Lr gene located on the long arm of wheat homoeologous group 2 chromosomes.