Phytopathology 

About: Phytopathology is an academic journal published by American Phytopathological Society. The journal publishes majorly in the area(s): Population & Plant virus. It has an ISSN identifier of 0031-949X. Over the lifetime, 15611 publications have been published receiving 530656 citations.

The Effect of Nitrogen Fertilization on the Expression of Slow-Mildewing Resistance in Knox Wheat

Abstract: SHANER, G., and R. E. FINNEY. 1977. The effect of nitrogen fertilization on the expression of slow-mildewing resistance in Knox wheat. Phytopathology 67: 1051-1056. Powdery mildew development on the slow-mildewing conditions disease severity increased greatly on Vermillion wheat cultivar Knox was compared to that on the susceptible but increased little on Knox. The area under the disease cultivar Vermillion over a period of 4 yr in the field at progress curve had a lower error variance than statistics Lafayette, Indiana. Cultivars received three levels of nitrogen associated with the logit transformation of severity data and fertilizer to determine if high levels of N affected the hence was a superior measurement of slow-mildewing. Slowexpression of slow-mildewing in Knox wheat. Knox's mildewing remains effective under the highest rates of resistance was evident under conditions favoring moderate to nitrogen fertilization likely to be applied to wheat. In severe disease on Vermillion. Under low nitrogen fertility or breeding for slow-mildewing, high rates of N provide optimal unfavorable weather there was little difference in level of conditions for recognition of this resistance. mildew on the two cultivars; under more favorable Additional key words: Erysiphe graminis, Triticum aestivum, epidemiology, general resistance, breeding for disease resistance, nitrogen fertilization effects. Wheat Triticum aestivum L. em. Thell. 'Knox' has cultivars with shorter and stiffer straw become available resistance to Erysiphe graminis f. sp. tritici that has been and because soil nitrogen level is an important factor in described as slow-mildewing to distinguish it from the mildew development (1, 4, 5, 6, 7, 8, 14). An additional resistance conferred by Pin genes (9). Because Knox has objective of this study was to find a way to measure slowmaintained its slow-mildewing character for many years mildewing suitable for use in a wheat breeding program. over a wide geographical area, this resistance appears to be race nonspecific and to have value for wheat breeding MATERIALS AND METHODS programs (3, 9, 10). Slow-mildewing in Knox is characterized by fewer successful infections and lower Wheat cultivars Knox (C. I. 12798) and Vermillion (C. spore production per colony, both of which restrict the I. 13080) were grown in four-row plots, each 2.4 m long rate of disease development in the field (10, 11). with 30 cm between rows. The plots were sown in Unfortunately, slow-mildewing is only a partial September on a fine sandy loam soil on the Purdue resistance, it is not expressed in seedlings, and it behaves Agronomy Farm, West Lafayette, Indiana. Potassium genetically as a quantitative trait (12). Moreover, Knox's and phosphorus were applied uniformly to the plot area slow-mildewing is a relative trait which can only be each fall in amounts adequate for high yield. Nitrogen (N) assessed by comparing mildew development on Knox and cultivar treatments were arranged in a split-plot with mildew development on a susceptible cultivar grown design with N levels as main plots and cultivars as under the same conditions. Because the rate of mildew subplots. Main plots were separated by four rows of the development depends on environment as well as host wheat cultivar Arthur, highly resistant to E. graminis. genotype, we would expect the measured level of slowShortly after emergence, a nitrogen topdress was applied mildewing in Knox to vary among years and locations, as follows: High-N (N3) plots received N as ammonium Therefore, we measured the slow-mildewing in Knox over nitrate at 100 kg/ha in 1971 and 1972 and 67 kg/ ha in a range of conditions favorable or unfavorable for the 1973 and 1974; intermediate-N (N2) plots received half disease to see if it would be expressed consistently. that amount each year; and low-N (NI) plots received Mildew development on Knox was compared with that none. In the spring, plots were topdressed as follows: N3, on the susceptible wheat cultivar Vermillion for 4 yr. Each 66 kg/ha in 1971 and 1972 and 90 kg/ ha in 1973 and 1974; year, three levels of nitrogen fertilizer were compared N2, half the amount applied to N3; and NI, none. About because farmers tend to use higher levels of nitrogen as mid-April wheat seedlings infected with an E. graminis culture collected in the field at Lafayette, Indiana in 1970 Copyright © 1977 The American Phytopathological Society, 3340 were placed between rows in each plot as a source of Pilot Knob Road, St. Paul, MN 55121. All rights reserved. inoculum. Beginning in early May and at weekly intervals

Induced Systemic Resistance and Promotion of Plant Growth by Bacillus spp.

Abstract: Kloepper, J. W., Ryu, C.-M., and Zhang, S. 2004. Induced systemic resistance and promotion of plant growth by Bacillus spp. Phytopathology 94:1259-1266. Elicitation of induced systemic resistance (ISR) by plant-associated bacteria was initially demonstrated using Pseudomonas spp. and other gram-negative bacteria. Several reviews have summarized various aspects of the large volume of literature on Pseudomonas spp. as elicitors of ISR. Fewer published accounts of ISR by Bacillus spp. are available, and we review this literature for the first time. Published results are summarized showing that specific strains of the species B. amyloliquefaciens, B. subtilis, B. pasteurii, B. cereus, B. pumilus, B. mycoides, and B. sphaericus elicit significant reductions in the incidence or severity of various diseases on a diversity of hosts. Elicitation of ISR by these strains has been demonstrated in greenhouse or field trials on tomato, bell pepper, muskmelon, watermelon, sugar beet, tobacco, Arabidopsis sp., cucumber, loblolly pine, and two tropical crops (long cayenne pepper and green kuang futsoi). Protection resulting from ISR elicited by Bacillus spp. has been reported against leaf-spotting fungal and bacterial pathogens, systemic viruses, a crown-rotting fungal pathogen, root-knot nematodes, and a stem-blight fungal pathogen as well as damping-off, blue mold, and late blight diseases. Reductions in populations of three insect vectors have also been noted in the field: striped and spotted cucumber beetles that transmit cucurbit wilt disease and the silver leaf whitefly that transmits Tomato mottle virus. In most cases, Bacillus spp. that elicit ISR also elicit plant growth promotion. Studies on mechanisms indicate that elicitation of ISR by Bacillus spp. is associated with ultrastructural changes in plants during pathogen attack and with cytochemical alterations. Investigations into the signal transduction pathways of elicited plants suggest that Bacillus spp. activate some of the same pathways as Pseudomonas spp. and some additional pathways. For example, ISR elicited by several strains of Bacillus spp. is independent of salicylic acid but dependent on jasmonic acid, ethylene, and the regulatory gene NPR1—results that are in agreement with the model for ISR elicited by Pseudomonas spp. However, in other cases, ISR elicited by Bacillus spp. is dependent on salicylic acid and independent of jasmonic acid and NPR1. In addition, while ISR by Pseudomonas spp. does not lead to accumulation of the defense gene PR1 in plants, in some cases, ISR by Bacillus spp. does. Based on the strains and results summarized in this review, two products for commercial agriculture have been developed, one aimed mainly at plant growth promotion for transplanted vegetables and one, which has received registration from the U.S. Environmental Protection Agency, for disease protection on soybean. Plant growth-promoting rhizobacteria (PGPR) are among the various groups of plant-associated microorganisms that can elicit plant defenses (28). In concert with the terminology used by van Loon and Glick in their recent review of PGPR (28), we will use the term induced systemic resistance (ISR) for the process whereby treatment of plants with PGPR elicits host defense as indicated by reduction in the severity or incidence of diseases caused by pathogens that are spatially separated from the inducing agent. With each of the cases of ISR elicited by Bacillus spp. discussed in this review, spatial separation of the pathogen from the bacteria was confirmed in the cited manuscript or in a previous manuscript with the same bacterial strain. In the 1990s, several PGPR-based products became commercially available in the United States, and more are currently under development. Most of these products contain strains of Bacillus PGPR. Earlier attempts to commercialize products containing fluorescent pseudomonad strains of PGPR generally failed due to lack of long-term viability of these asporogenous bacteria. Although commercialization of PGPR is mainly proceeding with Bacillus spp. rather than pseudomonads, the preponderance of research on PGPR as elicitors of growth promotion or ISR employs PGPR strains that are fluorescent pseudomonads. In this review, we summarize research on Bacillus PGPR. Our main emphasis is on Bacillus spp., which elicit ISR; however, since most such Bacillus spp. also promote plant growth, this review summarizes work on both growth promotion and ISR. We concentrate the review on refereed journal articles with some inclusion of previously unpublished work. The results of new work are marked as such in the review. Greenhouse reports of systemic disease protection. Workers

Overview of Mechanisms and Uses of Trichoderma spp.

Abstract: Fungi in the genus Trichoderma have been known since at least the 1920s for their ability to act as biocontrol agents against plant pathogens. Until recently, the principal mechanisms for control have been assumed to be those primarily acting upon the pathogens and included mycoparasitism, antibiosis, and competition for resources and space. Recent advances demonstrate that the effects of Trichoderma on plants, including induced systemic or localized resistance, are also very important. These fungi colonize the root epidermis and outer cortical layers and release bioactive molecules that cause walling off of the Trichoderma thallus. At the same time, the transcriptome and the proteome of plants are substantially altered. As a consequence, in addition to induction of pathways for resistance in plants, increased plant growth and nutrient uptake occur. However, at least in maize, the increased growth response is genotype specific, and some maize inbreds respond negatively to some strains. Trichoderma spp. are beginning to be used in reasonably large quantities in plant agriculture, both for disease control and yield increases. The studies of mycoparasitism also have demonstrated that these fungi produce a rich mixture of antifungal enzymes, including chitinases and beta-1,3 glucanases. These enzymes are synergistic with each other, with other antifungal enzymes, and with other materials. The genes encoding the enzymes appear useful for producing transgenic plants resistant to diseases and the enzymes themselves are beneficial for biological control and other processes.