Transcriptome and metabolome profiling of field-grown transgenic barley lack induced differences but show cultivar-specific variances.

The aim of the present study was to assess possible adverse effects of transgene expression in leaves of field-grown barley relative to the influence of genetic background and the effect of plant interaction with arbuscular mycorrhizal fungi. We conducted transcript profiling, metabolome profiling, and metabolic fingerprinting of wild-type accessions and barley transgenics with seed-specific expression of (1,3-1, 4)-beta-glucanase (GluB) in Baronesse (B) as well as of transgenics in Golden Promise (GP) background with ubiquitous expression of codon-optimized Trichoderma harzianum endochitinase (ChGP). We found more than 1,600 differential transcripts between varieties GP and B, with defense genes being strongly overrepresented in B, indicating a divergent response to subclinical pathogen challenge in the field. In contrast, no statistically significant differences between ChGP and GP could be detected based on transcriptome or metabolome analysis, although 22 genes and 4 metabolites were differentially abundant when comparing GluB and B, leading to the distinction of these two genotypes in principle component analysis. The coregulation of most of these genes in GluB and GP, as well as simple sequence repeat-marker analysis, suggests that the distinctive alleles in GluB are inherited from GP. Thus, the effect of the two investigated transgenes on the global transcript profile is substantially lower than the effect of a minor number of alleles that differ as a consequence of crop breeding. Exposing roots to the spores of the mycorrhizal Glomus sp. had little effect on the leaf transcriptome, but central leaf metabolism was consistently altered in all genotypes.

Tell me again what it is that you do.

My job at Pullman, Washington, starting in 1965, was to control the root diseases of wheat and barley, focusing first on fusarium root and crown rot, then including take-all and pythium and rhizoctonia root rots. In the absence of viable alternatives, the agronomic approaches used were implemented through design of cereal-based cropping systems. Starting in the late 1970s, the mission focused further on cereal-intensive direct-seed (no-till) cropping systems. A team effort demonstrated the role of indigenous antibiotic-producing fluorescent pseudomonads in the widespread decline of take-all in response to monoculture wheat (or barley-wheat sequences). Today, the suppression of take-all by these beneficial rhizobacteria is the centerpiece of an integrated system that augments take-all decline while limiting pythium and rhizoctonia root rots and fusarium root and crown rot in direct-seed systems. In such systems, "crop rotation" takes the form of different sequences of winter and spring wheat, barley and triticale varieties, and market classes, all susceptible to all four root diseases.

From the Academy: Colloquium perspective. Toward cropping systems that enhance productivity and sustainability.

The defining features of any cropping system are (i) the crop rotation and (ii) the kind or intensity of tillage. The trend worldwide starting in the late 20th century has been (i) to specialize competitively in the production of two, three, a single, or closely related crops such as different market classes of wheat and barley, and (ii) to use direct seeding, also known as no-till, to cut costs and save soil, time, and fuel. The availability of glyphosate- and insect-resistant varieties of soybeans, corn, cotton, and canola has helped greatly to address weed and insect pest pressures favored by direct seeding these crops. However, little has been done through genetics and breeding to address diseases caused by residue- and soil-inhabiting pathogens that remain major obstacles to wider adoption of these potentially more productive and sustainable systems. Instead, the gains have been due largely to innovations in management, including enhancement of root defense by antibiotic-producing rhizosphere-inhabiting bacteria inhibitory to root pathogens. Historically, new varieties have facilitated wider adoption of new management, and changes in management have facilitated wider adoption of new varieties. Although actual yields may be lower in direct-seed compared with conventional cropping systems, largely due to diseases, the yield potential is higher because of more available water and increases in soil organic matter. Achieving the full production potential of these more-sustainable cropping systems must now await the development of varieties adapted to or resistant to the hazards shown to account for the yield depressions associated with direct seeding.

Kenneth Frank Baker--pioneer leader in plant pathology.

Kenneth F. Baker (1908-1996) made major contributions to understanding diseases of ornamental plants, seed pathology, soil-borne plant pathogens, biological control, and history of plant pathology. His work set the stage for the success of today's ornamentals and nursery industries. His leadership and writings created the scientific framework for research and teaching on soil-borne plant pathogens and biological control. After B.Sc. and Ph.D. degrees from Washington State University in 1930 and 1934, respectively, and one year as a National Research Council Fellow with B.M. Dugger at Wisconsin, he took jobs in 1935 with the U.S. Department of Agriculture in Nebraska on establishment of shelter belts and 1936-39 with the Pineapple Producers Cooperative Association in Hawaii. He worked on diseases of ornamental plants at the University of California, Los Angeles, starting in 1939, moving to Berkeley in 1961 when the UCLA program closed. He retired in 1975 and moved to Corvallis, OR, as Emeritus Professor, Oregon State University, and Collaborator, U.S. Department of Agriculture, Agricultural Research Service. He spent four sabbatical leaves in Australia, and was elected fellow of the American Association for the Advancement of Science in 1950, fellow of the American Phytopathological Society in 1969, and the Horticultural Hall of Fame in 1976.

Yield Responses of Direct-Seeded Wheat to Rhizobacteria and Fungicide Seed Treatments.

Field trials were conducted with winter and spring wheat in eastern Washington and northern Idaho over several years to determine the benefit, as measured by grain yield, of seed treatments with rhizobacteria and formulated fungicides in cropping systems favorable to root diseases. The trials were conducted with wheat direct-seeded (no-till) in fields with a history of intensive cereals and one or more of the root diseases: take-all caused by Gaeumannomyces graminis var. tritici, Rhizoctonia root rot caused by Rhizoctonia solani AG8 and R. oryzae, and Pythium root rot caused mainly by Pythium irregulare and P. ultimum. The seed treatments included Bacillus sp. L324-92, Pseudomonas fluorescens Q69c-80, Pseudomonas fluorescens Q8r1-96, difenoconazole + metalaxyl (Dividend + Apron), difenoconazole + mefenoxam (Dividend + Apron XL = Dividend XL), tebuconazole + metalaxyl (Raxil XT), and tebuconazole + thiram (Raxil-thiram). Controls were nontreated seed planted into both nontreated (natural) soil and soil fumigated with methyl bromide just prior to planting. Although the data indicate a trend in higher wheat yields with two rhizobacteria treatments over the nontreated control (171 and 264 kg/ha, respectively), these higher yields were not significantly different from the nontreated control (P = 0.06). Fungicide seed treatments alone similarly resulted in yields that were 100 to 300 kg/ha higher than the nontreated control, but only the yield responses to Dividend on winter wheat (289 kg/ha) and Dividend + Apron on spring wheat (263 kg/ha) were significant (P ≤ 0.05). The greatest yield increases over the nontreated control occurred with certain rhizobacteria-fungicide combinations, with three treatments in the range of 312 to 486 kg/ha (6.1 to 17.7%; P ≤ 0.05). Some rhizobacteria-fungicide combinations brought average yields to within 85 to 90% of those obtained with soil fumigation. Only soil fumigation produced a measurable reduction in the incidence of take-all and Rhizoctonia root rot, as assessed on washed roots. No reliable method exists for visual quantification of Pythium root rot on wheat.

Advances in Plant Health Management in the Twentieth Century.

▪ Abstract Plant health management is the science and practice of understanding and overcoming the succession of biotic and abiotic factors that limit plants from achieving their full genetic potential as crops, ornamentals, timber trees, or other uses. Although practiced as long as agriculture itself, as a science-based concept, plant heath management is even younger than integrated pest management (IPM), and includes and builds upon but is not a replacement for IPM. Probably the greatest collection of success stories for plant health management is the number of diseases managed by cleaning up the planting material. The record for root health management is more mixed, with the loss or phase-out of soil fumigants, and practices such as crop rotation and clean tillage being replaced with more intensive cropping and less or no tillage. Perhaps the greatest scientific and technical advances for plant health management have come from the work aimed at management of the pathogens, pests, and other hazards that arrive by air. Flor's work on flax rust, which produced the gene-for-gene model, is possibly the most significant contribution of plant pathology to the life sciences in the twentieth century. Research aimed at the management of foliar pathogens is also the basis for modern theory on epidemiology, population biology, aerobiology, and disease prediction and decision-support systems. Even IPM arose mainly in response to the need to protect crops from pests that arrive by air. If the definition of biological control includes the plant induced or genetically modified to defend itself, as it should, then biological control has been the most significant approach to plant health management during the twentieth century and promises through modern biotechnology to be even more significant in the twenty-first century. Rather than "reducing losses," the advances are discussed here within the simple framework of achieving the attainable yield by increasing the actual and/or affordable and hence the average yield. Each of these four benchmark yields, as well as the absolute yield for crops, and their significance to the goals and achievements of plant health management are defined. Plant health management is a moving target, which I discuss metaphorically like an American football game, where one team is science and technology and the other is nature, where the S & T team is only beginning to know nature's rules while playing itself with the three sets of rules written to, respectively, satisfy the laws of economics, protect the environment, and gain social acceptance.