Abstracts of Selected Papers Relating to Fusarium Crown Rot

 

Hajihassani, A., R.W. Smiley, and F.J. Afshar. 2013. Effects of co-inoculations with Pratylenchus thornei and Fusarium culmorum on growth and yield of winter wheat. Plant Disease 97:1470-1477.

Growth and yield of winter wheat are suppressed by Pratylenchus thornei and by Fusarium culmorum. Many fields in cereal production regions throughout the world are infested by both pathogens. We evaluated effects of one or both pathogens on winter wheat growth, grain yield, and disease parameters at heading and harvest stages over two years in inoculated, rainfed pots incubated outdoors. Nematodes were inoculated at 1, 2, or 4 P. thornei/g of soil and F. culmorum was added at 0.65 g of colonized millet seed/kg of soil. At harvest, compared to the non-inoculated control, the high rate of P. thornei reduced (P < 0.05) plant height, shoot weight, root weight and grain yield by 19%, 17%, 48%, and 31%, respectively. F. culmorum alone reduced these parameters by 15%, 16%, 22%, and 22%. Co-inoculations caused reductions of 27%, 38%, 61%, and 63%. The reproductive rate or P. thornei was not greatly affected by co-inoculation with F. culmorum. Disease severity ratings at both plant growth stages became amplified as the nematode density was increased, and were much greater in the presence of both pathogens. Effects of co-inoculation on grain yield were slightly greater than predicted by additive effects of the individual pathogens, suggesting a synergistic effect on yield depression.

Smiley, R. W., Machado, S., Gourlie, J. A., Pritchett, L. C., Yan, G. P., and Jacobsen, E. E. 2013. Influence of semi-arid cropping systems on root diseases and inoculum density of soilborne pathogens. Plant Disease 97:547-555.

The 2-year rotation of rainfed winter wheat with cultivated fallow in the Pacific Northwest USA is slowly being changed into direct-seed (no-till) systems that include chemical fallow, spring cereals, and pulse and brassica crops. Eight cropping systems were compared over nine years to determine effects of changes on diseases. Fusarium crown rot was more prevalent in wheat following cultivated than chemical fallow, and Rhizoctonia root rot was more severe when winter wheat was rotated with chemical fallow than with no-till winter pea. Take-all occurred even during the driest years and was more severe on annual spring wheat than on annual spring barley. Inoculum density (pg DNA/g of soil) differed (α < 0.05) among cropping systems for Fusarium culmorum, F. pseudograminearum, Gaeumannomyces graminis var. tritici, and Pythium spp. but not for Rhizoctonia solani AG-8. Phoma medicaginis var. pinodella was detected only where winter pea was planted frequently. This is the first report of P. medicaginis as a component of the dryland stem rot complex of pea in north-central Oregon. Results of this investigation will provide guidance for developing crop species with resistance to Fusarium crown rot and black stem of pea.

Poole, G.J., Smiley, R.W., Walker, C., Huggins, D., Rupp, R., Abatzoglou, J., Garland-Campbell, K., and Paulitz, T.C.  2012.  Effect of climate on the distribution of Fusarium species causing crown rot of wheat in the Pacific Northwest of the US. Phytopathology 103: (submitted for peer review).

Fusarium crown rot is one of the most widespread root and crown diseases of wheat in the Pacific Northwest (PNW) of the U.S.  Fusarium crown rot occurrence and distribution has been associated with temperature and precipitation.  Our objectives were to characterize crown rot severity and distribution throughout the PNW by conducting a survey of 210 fields covering the diverse dryland wheat-producing areas of Washington and Oregon and to utilize a factor analysis statistical approach to determine the effects of climate and geography on species distribution and disease severity.  Climatic variables of mean annual temperature (MAT), mean temperature in the coldest month (MTCM), mean temperature in the warmest month (MTWM), mean annual precipitation (MAP), elevation, soil type and cropping intensity were highly intercorrelated and were used in a factor analysis. The factor analysis resulted in the development of two latent factors that could be used as predictor variables in linear mixed models with repeated measures of FCR disease scores and in generalized linear mixed models for the presence/absence of Fusarium spp. Isolates of Fusarium spp. were obtained from 99% of 105 fields sampled in 2008 and 97% of fields in 2009.  Results of the factor analysis showed that the distribution of F. pseudograminearum occurred in a greater frequency in areas of the PNW at lower elevations with lower moisture and higher temperatures, whereas F. culmorum occurred in greater frequency from areas at higher elevations with moderate to high moisture and cooler temperatures.  This factor analysis approach can be utilized in studies to describe the effects of climate and other environmental (soil, cropping system, etc.) factors on the distribution and severity of root diseases.

Poole, G.J., R.W. Smiley, T.C. Paulitz, C.A. Walker, A.H. Carter, D.R. See, and K. Garland-Campbell. 2012. Identification of quantitative trait loci (QTL) for resistance to Fusarium crown rot (Fusarium pseudograminearum) in multiple assay environments in the Pacific Northwestern US. Theoretical & Applied Genetics 125:91-107.

Fusarium crown rot (FCR), caused by Fusarium pseudograminearum and F. culmorum, reduces wheat (Triticum aestivum L.) yields in the Pacific Northwest (PNW) of the US by as much as 35%. Resistance to FCR has not yet been discovered in currently grown PNW wheat cultivars. Several significant quantitative trait loci (QTL) for FCR resistance have been documented on chromosomes 1A, 1D, 2B, 3B, and 4B in resistant Australian cultivars. Our objective was to identify QTL and tightly linked SSR markers for FCR resistance in the partially resistant Australian spring wheat cultivar Sunco using PNW isolates of F. pseudograminerarum in greenhouse and field based screening nurseries. A second objective was to compare heritabilities of FCR resistance in multiple types of disease assaying environments (seedling, terrace, and field) using multiple disease rating methods. Two recombinant inbred line (RIL) mapping populations were derived from crosses between Sunco and PNW spring wheat cultivars Macon and Otis. The Sunco/Macon population comprised 219 F6:F7 lines and the Sunco/Otis population comprised 151 F5:F6 lines. Plants were inoculated with a single PNW F. pseudograminearum isolate (006-13) in growth room (seedling), outdoor terrace (adult) and field (adult) assays conducted from 2008 through 2010. Crown and lower stem tissues of seedling and adult plants were rated for disease severity on several different scales, but mainly on a numeric scale from 0 to 10 where 0 = no discoloration and 10 = severe disease. Significant QTL were identified on chromosomes 2B, 3B, 4B, 4D, and 7A with LOD scores ranging from 3 to 22. The most significant and consistent QTL across screening environments was located on chromosome 3BL, inherited from the PNW cultivars Macon and Otis, with maximum LOD scores of 22 and 9 explaining 36 and 23% of the variation, respectively for the Sunco/Macon and Sunco/Otis populations. The SSR markers Xgwm247 and Xgwm299 flank these QTL and are being validated for use in marker-assisted selection for FCR resistance. This is the first report of QTL associated with FCR resistance in the US.

Smiley, R.W. 2009. Water and temperature parameters associated with winter wheat diseases caused by soilborne pathogens. Plant Disease 93:73-79.

ABSTRACT
Wheat in eastern Oregon is produced mostly as a 2-year rotation of winter wheat and summer fallow. Maximum agronomic yield potential is expected with early September planting dates but actual yields are generally highest for plantings made in mid-October. Field experiments with sequential planting dates from early September to December were performed over four years. Associations among yield, disease incidence, and 19 moisture and temperature parameters were evaluated. Incidence of Cephalosporium stripe, crown rot, eyespot and take-all decreased as planting was delayed. Crown rot and eyespot were negatively correlated more significantly and frequently with temperature than moisture parameters, and take-all was more associated with moisture than temperature. Rhizoctonia root rot was unrelated to planting date and climatic parameters. Crown rot was identified most frequently (four of five tests) as an important contributor to yield suppression, but yield was most closely associated (R2 > 0.96) with effects from a single disease in only two of five location-year tests. Yield was most related to combinations of diseases in three of five tests, complicating development of disease modules for wheat growth-simulation models.

Smiley, R.W. and Yan, H. 2009. Variability of Fusarium crown rot tolerances among cultivars and lines of spring and winter wheat. Plant Disease 93:954-961. 

ABSTRACT
Crown rot caused by Fusarium pseudograminearum reduces the yield of wheat in Oregon. Observations of crown rot symptoms in traditional breeding and yield testing nurseries have not been useful for describing tolerance ratings of wheat cultivars. Yield data from inoculated experiments were therefore evaluated to determine if differences in cultivar response could be identified. A comparison of yields in inoculated and noninoculated plots was made for one group of spring wheat entries and four groups of winter wheat entries. Significant differences among spring wheat entries were identified and were validated against standards for tolerance and intolerance to F. pseudograminearum in Australia. Locally adapted and Australian standards exhibited a comparable range of yield reduction due to inoculation. Spring wheat tolerance reactions can be accurately described using as few as 24 yield comparisons. However, this screening method will not be practical for winter wheat due to stronger effects of year and location on the phenotypic tolerance response, requiring about 95 yield comparisons to accurately define the crown rot phenotype of a winter wheat cultivar. 

Smiley, R.W., J.A. Gourlie, S.A. Easley, L.-M. Patterson, and R.G. Whittaker. 2005. Crop damage estimates for crown rot of wheat and barley in the Pacific Northwest. Plant Disease 89:595-604.

ABSTRACT
Crown rot of wheat and barley in the Pacific Northwest is caused by a complex of Fusarium pseudograminearum, F. culmorum and Bipolaris sorokiniana. Yield-loss estimates were made by evaluating yield components on tillers collected from commercial fields and sorted by disease severity classes, and by comparing yields for field plots inoculated with F. pseudograminearum with yields in naturally infested soil. Increasing crown rot severity caused an increase in grain protein content and reduction in grain yield, kernels per head, kernel weight, test weight, tiller height, and straw weight. Crown rot reduced winter wheat yield as much as 1,550 kg/ha (35%, $219/ha) in commercial fields, with a 13-field mean of 9.5% ($51/ha). Inoculation reduced yields as much as 2,630 kg/ha (61%, $372/ha) over that caused by the native pathogen flora. Rain-induced crusting of the soil surface greatly amplified pre-emergence damping-off caused by F. pseudograminearum. Crown rot caused greatest losses during seasons of lowest precipitation but also damaged crops under wet conditions. Above-ground symptoms were not always apparent under conditions of moderate infection and yield constraint. Damage from crown rot in the Pacific Northwest is more widespread and damaging than previously recognized.

Smiley, R.W., J.A. Gourlie, S.A. Easley, and L.-M. Patterson. 2005. Pathogenicity of fungi associated with the wheat crown rot complex in Oregon and Washington. Plant Disease 89:949-957.

ABSTRACT
Crown rot of wheat in the Pacific Northwest is caused by a complex including Bipolaris sorokiniana, Fusarium avenaceum, F. culmorum, F. pseudograminearum and Microdochium nivale. Relative pathogenicity was examined under greenhouse conditions for 178 isolates of the five species, and under field conditions for 24 isolates of B. sorokiniana, F. culmorum and F. pseudograminearum. In the greenhouse, all five species reduced (P < 0.05) plant height relative to noninoculated controls. Disease severity was inversely correlated with plant height for the three Fusarium species. In one or more of four experiments with spring wheat in the field, all three species reduced stand establishment and density of mature heads, and increased the incidence and severity of crown rot. Fusarium culmorum and F. pseudograminearum caused the greatest disease severity and plant damage and were the only pathogens that reduced grain yield. Virulence ratings were variable among isolates for each species in all greenhouse and field experiments. Isolate variability was especially high for the location and year variables in field experiments. Mixtures of multiple isolates are required for future research.

Smiley, R., M. Siemens, T. Gohlke, and J. Poore. 2005. Small Grain Acreage and Management Trends for Eastern Oregon and Washington. Oregon Agric. Exp. Sta. Spec. Pub. 1061:30-50.

ABSTRACT
Small grain acreage and management trends over the past 20 years were evaluated for counties and regions in eastern Oregon and Washington. Data were obtained from surveys conducted by the Conservation Technology Information Center (CTIC) and National Agricultural Statistics Service (NASS). Small grain acreages of dryland and irrigated winter wheat, spring wheat, and barley are reported as a percent of the total acreage in each region of each state. Also reported are trends for tillage practices, cropping frequency, and timing in terms of percent of total acreage. Winter wheat acreage has remained relatively constant over the last 20 years for most regions and comprised over 60 percent of the nearly 3.5 million acres planted to small grains in eastern Oregon and Washington. Acreage planted to barley has generally declined by 5 percent, with production shifting to spring wheat. Use of intensive tillage has decreased by over 50 percent in most regions, with production shifting to reduced tillage and no-till. No-till acreage for all wheat in Oregon increased from 1 percent in 1996 to 17 percent in 2004 and from 3 percent to 13 percent in Washington. For spring wheat, no-till acreage increased from 2 to 21 percent in Oregon and from 2 to 18 percent in Washington.

Smiley, R.W., J.A. Gourlie, R.G. Whittaker, S.A. Easley, and K.K. Kidwell. 2004. Economic impact of Hessian fly (Diptera: Cecidomyiidae) on spring wheat in Oregon and additive yield losses with Fusarium crown rot and lesion nematode. Journal of Economic Entomology 97:397-408.

ABSTRACT
Damage caused by Hessian fly, Mayetiola destructor (Say), was quantified in spring wheat, Triticum aestivum L., trials near Pendleton and Moro, OR, during 2001 and 2002. Five field experiments were established to examine genetic resistance to Fusarium crown rot, Fusarium pseudograminearum (O'Donnell & Aoki), and economic damage by lesion nematodes, Pratylenchus neglectus ((Rensch, 1924) Filipjev Schuurmanns & Stekhoven, 1941) and P. thornei (Sher & Allen, 1941). Hessian fly became the dominant factor affecting grain yield in four experiments. Genotypes carrying the H3-resistance gene had grain yields 66% and 68% higher than susceptible genotypes in cultivar trials during 2001 and 2002, respectively. Yield reductions were detected when Hessian fly infestation rates exceeded 50% plants during 2001 and 15% plants (8% tillers) during 2002. In two trials during 2001, in-furrow application of aldicarb (Temik) at planting improved yields of four Hessian fly-susceptible cultivars by 72% and 144% (up to 1,959 kg/ha) and yields of one Hessian fly-resistant cultivar by 2% and 3%. Resistant cultivars and aldicarb improved grain quality as much as two market grades during 2001. The value of increased grain production with Hessian fly-resistant cultivars in four field experiments ranged from $112 to $252/ha, excluding price incentives for improved market quality. Yield reduction due to combined damage from Hessian fly and either Fusarium crown rot or lesion nematode was additive. This report seams to be the first quantitative yield loss estimate for Hessian fly in spring wheat in the semiarid environment of the inland Pacific Northwest. 

Paulitz, T.C., R.W. Smiley, and R.J. Cook. 2002. Insights into the prevalence and management of soilborne cereal pathogens under direct seeding in the Pacific Northwest, USA. Canadian Journal of Plant Pathology 24:416-428.

ABSTRACT
Direct seeding or no-till leaves the soil undisturbed, except where the seed is planted and the soil fertilized. It offers several advantages in small-grain cereal production, including reduction in labor and other operating costs, reduction in soil erosion, and improvement of soil quality. However, only about 10% of small grains in the U.S.A., and 6% of the small grains in the Pacific Northwest region of the U.S.A. are currently direct seeded. Root diseases are major constraints to adoption of direct seeding; they increase because of lack of tillage, increased crop residue left on the surface, and typically cooler and wetter soil conditions in the spring. This review covers some recent research on the four most important root diseases of cereals in the Pacific Northwest and their causal agents. These diseases are rhizoctonia root rot and bare patch [Rhizoctonia solani AG-8, Rhizoctonia oryzae], pythium damping-off and root rot [Pythium spp.], take-all [Gaeumannomyces graminis var. tritici], and fusarium foot rot [Fusarium pseudograminearum and Fusarium culmorum]. We discuss how these diseases are affected by direct seeding and the impact of management strategies, including crop rotation, residue management, control of inoculum from volunteers and weeds, fertilizer placement, genetic tolerance, biological control, development of natural suppressiveness, and prediction of risk through DNA-based detection methods.  

Smiley, R.W., and Patterson, L.-M. 1996. Pathogenic fungi associated with Fusarium foot rot of winter wheat in the semiarid Pacific Northwest USA. Plant Disease 80:944-949.

ABSTRACT
Winter wheat plants and soil were collected from 288 non-irrigated fields in the semiarid Pacific Northwest (PNW) during 1993 and 1994. Fungi associated with 5,390 crown and subcrown internodes from 10 Oregon and nine Washington counties were identified. Fusarium graminearum Group 1 was most widespread and the dominant pathogen associated with a crown and root rot named Fusarium foot rot or dryland root rot. F. culmorum was widely distributed in soil but was detected in plants in only half as many locations as F. graminearum. Other pathogens included Bipolaris sorokiniana, Microdochium nivale and F. avenaceum. Highly variable isolation frequencies for all five pathogens was presumed related to a very dry and a very wet survey year. Each pathogen was considered dominant or co-dominant at one or more sites during one or more years. All five species and F. acuminatum and F. oxysporum included isolates capable of killing wheat seedlings in the greenhouse.
     [Note: Fusarium pseudograminearum is the currently accepted name for the fungus discussed in this abstract as either "F. graminearum Group 1" or "F. graminearum" ]

Smiley, R.W., H.P. Collins, and P.E. Rasmussen. 1996. Diseases of wheat in long-term agronomic experiments at Pendleton, Oregon. Plant Disease 80:813-820.

ABSTRACT
Diseases of winter wheat were evaluated over 3 years in four long-term (27- to 60-year) cropping system experiments. Disease incidence and severity were evaluated with respect to seasonal precipitation and soil chemical and microbiological parameters. Take-all and eyespot were associated with increasing precipitation, and Rhizoctonia root rot and Fusarium crown rot were favored by drought. Eyespot and crown rot increased with rate of applied nitrogen and were inversely proportional to soil pH. Surface residue from previous crops had variable effects on diseases. Crown rot increased with amount of surface residue and was directly correlated with soil organic nitrogen and carbon. Surface residue also had a variable effect on Rhizoctonia root rot, depending on magnitude of soil microbial respiration; root rot increased directly with amount of residue in a wheat-summer fallow rotation and was unaffected by residue and/or tillage in a wheat-pea rotation. Repeated burning of wheat stubble caused variable disease response, depending on precipitation and nitrogen rate. At high fertility, burning suppressed Pythium root rot and Rhizoctonia root rot, and enhanced eyespot and take-all. Effects of crop rotations on diseases appeared related to soil microflora effects on pathogen survival or virulence. Rhizoctonia root rot was most damaging in wheat-fallow rotation, Pythium root rot in wheat-fallow and annual wheat, and eyespot and crown rot in annual wheat. Diseases were collectively least prevalent where nitrogen in a wheat-fallow rotation was applied as pea vines or manure, rather than as inorganic fertilizer. Diseases also were generally less damaging in a wheat-pea rotation than in annual wheat or wheat-fallow rotation. Soilborne plant pathogenic fungi appeared to suppress wheat yield by 3 to 12%. Long-term experiments provided insights to crop management and seasonal effects that are unlikely to be identified in short-term experiments.
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