Download or read book Initiation and Spread of Footrot of Wheat Caused by Cercosporella Herpotrichoides Fron written by Randall Charles Rowe and published by . This book was released on 1973 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Initiation and Spread of Footrot of Wheat Caused by Cercosporella Herpotrichoides written by Randall Charles Rowe and published by . This book was released on 1972 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Footrot of wheat (Cercosporella herpotrichoides Fron) is a major disease of winter wheat in certain areas of the world having a cool, damp winter and early spring climate. In Oregon, it is an economic problem in the higher rainfall wheat-growing areas in the eastern portion of the state. This study was undertaken to obtain basic information concerning inoculum production, initiation of infection and epidemic development of this disease. The activity of the fungus is strongly controlled by its microclimate, requiring cool, damp conditions for optimal activity. Temperature is the primary factor regulating inoculum production, as abundant moisture is not usually a limiting factor under field conditions from late fall through early spring. Maximum sporulation occurred at 10 C, decreased to insignificant amounts above 20 C and ceased below 0 C and above 30 C. Under fluctuating temperatures, abundant sporulation continued when day temperatures were in the optimal range (8-12 C), as long as the duration of sub-0 C night temperatures ( -5 C) did not exceed 14 hrs. A method of evaluating fluctuating temperature regimes was developed by calculating Daily Thermal Sporulation Coefficients (DTSC). The amount of sporulation is a function of the total hours of favorable and unfavorable temperatures that occur daily as reflected by DTSC values. Active sporulation periods are defined as periods of at least 2-3 weeks duration in which the humidity near the soil remains near saturation, the air temperature is above freezing for more than 8 hrs /day, and the average DTSC is above 50. Maximum sporulation levels can be maintained continuously up to 50 days under these conditions. Sporulation periods were identified from field temperature data and used to assess seasonal epidemic potential. The temperature range over which infection can occur is identical to that for sporulation. Infection requires free moisture and is stimulated by the presence of exogenous nutrients, while continued high humidity favors lesion development. All aerial plant tissues, including leaf blades, are susceptible to infection if these requirements are met; susceptibility increasing with tissue age. Infection occurs naturally at the base of the plant by colonization of senescent leaf sheaths, enabling the fungus to establish a food base and increase its infection potential. Rapid colonization of these tissues also provides a protected infection court free from moisture stress, enabling the fungus to overcome the resistance of underlying green tissues. Movement of infection from point sources of inoculum was evaluated in the field. Slopes of disease gradients calculated by plotting the log percent infection against the log distance from the inoculum source were less than slopes calculated from a rain splash model system and decreased throughout the growing season. The effective dispersal range of the fungus was only 3-4 feet. Plants located 3 feet from the inoculum source showed 50% infection 88 days later than those located 1 foot away. Apparent infection rates (r) were low (.005-.011) as compared with cereal rusts (. 100 -. 500). An increase in r was noted in mid-spring in plots with inoculum but not in plots where the inoculum was removed. This indicates that early spring as well as late fall is an important infection period. Analysis of the data fits Van der Plank's "simple interest" model which suggests no role for secondary inoculum in the disease cycle. This is supported by field observations showing abundant sporulation on stubble and negligible amounts on new lesions.
Download or read book Etiological Studies on Foot Rot of Wheat Caused by Cercosporella Herpotrichoides Fron written by Ralph S. Byther and published by . This book was released on 1968 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abundant conidial production occurs from colonized straws and plants infected with Cercosporella herpotrichoides Fron during the cool moist months of the growing season. Experiments were designed to study the survival, inoculum potential and competitive saprophytic ability of conidia in soil. Laboratory results indicated that cool moist soil favors the saprophytic survival of the fungus in soil. Viable hyphae were observed 16 months after conidia were buried in soil held at 5° and 10° C. Ammonium nitrate inhibited germination and survival of conidia in soil. It also inhibited germination on glass slides not in contact with soil. Ammonium ions were more inhibitory than nitrate ions. Glucose did not influence germination but stimulated saprophytic development and survival of the pathogen in soil. A marked reduction in survival of C. herpotrichoides after one year occurred in naturally and artificially colonized straws buried in the soil. Survival was favored in straws placed at the soil surface. Straws buried in conidial infested soil and incubated in the laboratory or the field were colonized by the pathogen. Colonization was directly related to the inoculum density of the soil and inversely related to time. Foot rot lesions developed below the soil surface on plants grown in conidial infested soil. Lesion incidence was directly related to the inoculum density of the soil. Based on mathematical models it was concluded that conidia were influenced by host exudates only at the host surface and a rhizosphere was not operative. The fungus was able to grow up to 10 mm from a food base in the soil and cause below ground lesions. Lesions below the soil surface were observed on plants growing under natural field conditions. It is suggested these below ground infections play an important part in maintaining inoculum levels in fields during years not favorable for foot rot development. In growth chamber studies, plants developed lesions from single conidium inoculations. Disease development on plants in the growth chamber was influenced by the general susceptibility of the inoculated tissue, the stage of growth when inoculated, the rate of plant growth and the openness of the crown. Green tissues were more resistant to infection than senescent tissues. Infection occurring before the onset of tillering can result in lesion development on each new tiller produced. Plants growing rapidly in a high nitrogen media were able to slough off infections and escape the disease. Tight crowned plants tended to have a majority of their tillers infected while healthy culms were associated with diseased ones in plants having wide spreading crowns. Successful penetration and infection of a coleoptile or leaf sheath did not insure disease development. The infected tissues may become separated from the main stem before the fungus has penetrated into adjacent leaf sheaths, thus isolating the pathogen, so that.the majority of the plant tissue escapes infection. The infection process failed at one of three stages on green "resistant" tissues of coleoptiles and leaf sheaths: (1) germination failed to occur, (2) germination occurred but the pathogen failed to attempt penetration, and (3) penetration was attempted but failed. Thickening of host cell walls was associated with the failure of attempted penetrations. Thickened host walls were also associated with containment of the pathogen at the perifery of lesions. These thickened cell walls usually stained heavily with cotton blue and were never associated with senescent tissue. Results indicate that stubble mulching and deep seeding would favor foot rot development. Chemicals or varieties delaying senescence of leaf sheaths would be expected to reduce foot rot injury.
Download or read book Investigations on Footrot of Winter Wheat Caused by Cercosporella Herpotrichoides Fron written by Lester Emert Dickens and published by . This book was released on 1957 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Breeding for Disease Resistance written by R. Johnson and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is an increasing need for an understanding of the fundamental processes involved in the mechanisms by which disease resistances are introduced into crop plants. This book provides a wide-ranging coverage of the successes and failures of the classical techniques; it describes the advances towards modern technology and addresses the problems of pathogen variation. Crop plants that are considered include: cereals (wheat, barley, rice), potatoes, vegetables and soft fruits.
Download or read book American Doctoral Dissertations written by and published by . This book was released on 1972 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book O S U Theses and Dissertations 1970 1977 written by Oregon State University and published by . This book was released on 1980 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Comprehensive Dissertation Index written by and published by . This book was released on 1984 with total page 1086 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vols. for 1973- include the following subject areas: Biological sciences, Agriculture, Chemistry, Environmental sciences, Health sciences, Engineering, Mathematics and statistics, Earth sciences, Physics, Education, Psychology, Sociology, Anthropology, History, Law & political science, Business & economics, Geography & regional planning, Language & literature, Fine arts, Library & information science, Mass communications, Music, Philosophy and Religion.
Download or read book Durability of Disease Resistance written by Th. Jacobs and published by Springer Science & Business Media. This book was released on 2012-02-02 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: From February 24 -28, 1992 an international symposium on Durability of Disease Resistance was held at the International Agricultural Centre in Wageningen, the Netherlands. The symposium, organized by the Department of Plant Breeding of Wageningen Agricultural University and the Centre for Plant Breeding and Repro duction Research, CPRO-DLO, was part of the DGIS funded programme Durable Resistance in Developing Countries. Without any form of prevention or protection nearly all crops will be seriously or even severely damaged by a range of pathogens. In modern agriculture man has been able to control many if not most pathogens using i) pesticides, ii) phyto sanitary methods such as control of seed and plant material in order to start a crop disease free, iii) agronomic measures such as crop rotation, iv) disease resis tance or combinations of these measures. Over the years the use of pesticides has increased enormously and so did the pro blems associated with pesticide use, such as environmental pollution and building of resistance and tolerance to these pesticides in the pathogens. The use of resis tance too increased strongly over the years and here too problems arose.
Download or read book Integrated Disease Management of Wheat and Barley written by Richard Oliver and published by Burleigh Dodds Series in Agric. This book was released on 2018-09-21 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diseases remain a serious problem in cereal cultivation. The first parts of the book review current research on fungal diseases of cereals and the challenge of fungicide resistance. The book then discusses breeding resistant varieties and methods for integrated disease management of cereals.
Download or read book Comprehensive Dissertation Index Agriculture written by and published by . This book was released on 1984 with total page 1080 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Internationaal Symposium over Fytofarmacie en Fytiatrie written by and published by . This book was released on 1979 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Annual Review of Phytopathology written by Kenneth P. Baker and published by . This book was released on 1974 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mededeling written by and published by . This book was released on 1975 with total page 844 pages. Available in PDF, EPUB and Kindle. Book excerpt: Consists of articles reprinted from various other journals.
Download or read book National Agricultural Library Catalog written by National Agricultural Library (U.S.) and published by . This book was released on 1981 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cornell Extension Bulletin written by and published by . This book was released on 1961 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cornell Extension Bulletin written by New York State College of Agriculture. Extension Service and published by . This book was released on with total page 914 pages. Available in PDF, EPUB and Kindle. Book excerpt:
