Wheat Stem Bases Research Articles

Velvet Family Protein FpVelB Affects Virulence in Association with Secondary Metabolism in Fusarium pseudograminearum.

Fusarium pseudograminearum causes destructive crown disease in wheat. The velvet protein family is a crucial regulator in development, virulence, and secondary metabolism of fungi. We conducted a functional analysis of FpVelB using a gene replacement strategy. The deletion of FpVelB decreased radial growth and enhanced conidial production compared to that of wild type. Furthermore, FpVelB modulates the fungal responses to abiotic stress through diverse mechanisms. Significantly, virulence decreased after the deletion of FpVelB in both the stem base and head of wheat. Genome-wide gene expression profiling revealed that the regulation of genes by FpVelB is associated with several processes related to the aforementioned phenotype, including "immune", "membrane", and "antioxidant activity", particularly with regard to secondary metabolites. Most importantly, we demonstrated that FpVelB regulates pathogen virulence by influencing deoxynivalenol production and modulating the expression of the PKS11 gene. In conclusion, FpVelB is crucial for plant growth, asexual development, and abiotic stress response and is essential for full virulence via secondary metabolism in F. pseudograminearum.

A comparison between the role of enniatins and deoxynivalenol in Fusarium virulence on different tissues of common wheat

BackgroundFusarium graminearum and Fusarium avenaceum are two of the most important causal agents of Fusarium head blight (FHB) of wheat. They can produce mycotoxins that accumulate in infected wheat heads, including deoxynivalenol (DON) and enniatins (ENNs), produced by F. graminearum and F. avenaceum, respectively. While the role of DON as a virulence factor in F. graminearum toward wheat is well known, ENNs in F. avenaceum has been poorly explored. Results obtained to-date indicate that ENNs may confer an advantage to F. avenaceum only on particular hosts.ResultsIn this study, with the use of ENN-producing and ENN non-producing F. avenaceum strains, the role of ENNs on F. avenaceum virulence was investigated on the root, stem base and head of common wheat, and compared with the role of DON, using DON-producing and DON non-producing F. graminearum strains. The DON-producing F. graminearum strain showed a significantly higher ability to cause symptoms and colonise each of the tested tissues than the non-producing strain. On the other hand, the ability to produce ENNs increased initial symptoms of the disease and fungal biomass accumulation, measured by qPCR, only in wheat heads, and not in roots or stem bases. LC-MS/MS analysis was used to confirm the presence of ENNs and DON in the different strains, and results, both in vitro and in wheat heads, were consistent with the genetics of each strain.ConclusionWhile the key role of DON on F. graminearum virulence towards three different wheat tissues was noticeable, ENNs seemed to have a role only in influencing F. avenaceum virulence on common wheat heads probably due to an initial delay in the appearance of symptoms.

Antagonistic effects of Talaromyces muroii TM28 against Fusarium crown rot of wheat caused by Fusarium pseudograminearum.

Fusarium crown rot (FCR) caused by Fusarium pseudograminearum is a serious threat to wheat production worldwide. This study aimed to assess the effects of Talaromyces muroii strain TM28 isolated from root of Panax quinquefolius against F. pseudograminearum. The strain of TM28 inhibited mycelial growth of F. pseudograminearum by 87.8% at 72 h, its cell free fermentation filtrate had a strong antagonistic effect on mycelial growth and conidial germination of F. pseudograminearum by destroying the integrity of the cell membrane. In the greenhouse, TM28 significantly increased wheat fresh weight and height in the presence of pathogen Fp, it enhanced the antioxidant defense activity and ameliorated the negative effects of F. pseudograminearum, including disease severity and pathogen abundance in the rhizosphere soil, root and stem base of wheat. RNA-seq of F. pseudograminearum under TM28 antagonistic revealed 2,823 differentially expressed genes (DEGs). Most DEGs related to cell wall and cell membrane synthesis were significantly downregulated, the culture filtrate of TM28 affected the pathways of fatty acid synthesis, steroid synthesis, glycolysis, and the citrate acid cycle. T. muroii TM28 appears to have significant potential in controlling wheat Fusarium crown rot caused by F. pseudograminearum.

RNA-Pol II Transcription Elongation Factor FpRtfA Is Required for Virulence and Secondary Metabolism in Fusarium pseudograminearum

The soil-borne pathogen Fusarium pseudograminearum is capable of causing a highly destructive crown disease in wheat. The purpose of this study was to characterize the biological functions, such as of virulence and secondary metabolites (SMs), of a putative RNA-Pol II transcription elongation factor, FpRtfA, in F. pseudograminearum. The current study revealed that the deletion of FpRtfA reduced radial growth compared to wild type in F. pseudograminearum. In addition, FpRtfA was found important to conidiation and response to metal ions and oxidative stress. More importantly, the virulence to the wheat stem base or head was decreased when FpRtfA was deleted. Using genome-wide gene expression profiling, FpRtfA was found to regulate several processes related to the above phenotype, such as the carbohydrate metabolic process, and the response to oxidative stress and oxidoreductase activity, especially for SMs. Further, we proved that FpRtfA exerts its regulatory effect on the virulence of pathogens by modulating the expression of the PKS gene, but not the generation of DON. In conclusion, FpRtfA has important roles in growth, asexual development, and the response to metal ions and oxidative stress. More importantly, FpRtfA is required for SMs and full virulence in F. pseudograminearum.

The global regulator FpLaeB is required for the regulation of growth, development, and virulence in Fusarium pseudograminearum.

Fusarium pseudograminearum is a soil-borne pathogen that is capable of causing a highly destructive crown disease in wheat. Secondary metabolites (SMs), especially deoxynivalenol (DON), are the primary virulence factors during infection. Here, we characterised the global regulator FpLaeB, an orthologue of LaeB protein function, to regulate the SM in Aspergillus nidulans. Through the utility of the gene targeting approach, we found that the vegetative growth of the FpLaeB deletion mutant was drastically reduced compared to that of the wild type. FpLaeB was also important for conidiation because the FpLaeB deletion mutant formed fewer conidia in induced medium. In addition, the sensitivity of the FpLaeB deletion mutant to the cell wall integrity inhibitor was decreased, while its growth was more severely inhibited by the cell membrane inhibitor sodium dodecyl sulfate (SDS) than that of the wild type. More importantly, the virulence was decreased when the FpLaeB deletion mutant was inoculated onto the wheat stem base or head. Through genome-wide gene expression profiling, FpLaeB was found to regulate several processes related to the above phenotypes such as the carbohydrate metabolic process, which is an integral and intrinsic component of membranes, especially SMs. Furthermore, the generation of DON was impaired in the FpLaeB deletion mutant via ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay. These results showed that FpLaeB plays an important role in the growth, development, and maintenance of the cell wall, and in membrane integrity. More importantly, FpLaeB is required for SMs and full virulence in F. pseudograminearum.

Wheat stem base diseases and their causal agents

Wheat stem base disease is an important disease complex, caused by various pathogens that are characterized by variable life cycles and ecological requirements. Wheat stem bases with symptoms of different stem diseases were collected in 2012-2018. Causal agents and other fungi were identified by mycological and molecular genetic methods. A total of 6787 isolates of fungi were obtained and identified to the genera/species level. Out of the total number of isolates, 50% belonged to causal agents of stem base diseases, 10% were causal agents of leaf spots, and 8% were different saprotrophs. Fungi from the genera Fusarium (51%) and Oculimacula (35%) were the most dominant causal agents of stem base diseases. An increasing occurrence of Microdochium nivale and M. bolleyi (totally 15%) was noticed. The dominant species of Fusarium were F. culmorum, F. avenaceum and F. tricinctum; other species were detected only in some cases. An unexpectedly high proportion (31%) of fungi from different ecological niches were isolated from wheat stems with stem base disease symptoms. Phaeosphaeria (most likely P. pontiformis) was the dominant fungus among non-pathogenic fungi. Further studies are required to clarify the interactions between this fungus, wheat, and causal agents of stem base diseases.

Incidence of Fusarium foot and root rot of cereals under conservation agriculture in north west Tunisia.

Conservation agriculture, based on direct drilling for crop establishment, has emerged in Tunisia since 1999/2000 as an alternative to conventional agriculture based on conventional drilling. The main objective of this approach is to ensure yield stability from crops and replenishment of soil organic matter. Previous research has demonstrated increased risks from pathogens favoured by mulching. The impacts of direct drilling on yields, and Fusarium foot and root rot of durum wheat, oat and barley, were studied over three successive growing seasons (2009/10, 2010/11, 2011/12) in northwest Tunisia. Disease incidence was estimated by the recovery frequency of Fusarium spp. isolates from stem bases and roots of plants of the three cereals. In addition, disease severity was assessed by occurrence of whiteheads that senesced prematurely, and the browning intensity on durum wheat stem bases. Grain yields were recorded at the ripening stages. Fusarium culmorum and F. pseudograminearum were isolated from the three cereals, with F. culmorum being the dominant pathogen . Direct drilling increased the incidence (60%) of these pathogens on stem bases and roots during the warmer seasons of 2009/10 and 2010/11, but less infection (37%) compared to conventional drilling was observed in the wetter season of 2011/12. Direct drilling increased the percentage of whiteheads of durum wheat (73%), but did not affect disease severity, which was estimated by the discolouration on stem bases and grain yield.

Effects of soil tillage and crop rotation on the development of wheat stem base diseases

Wheat stem base disease (WSD) is an important disease complex which can be caused by various pathogens with variable life cycles, ecological requirements and sensitivities to fungicides. Agronomic practices are considered important tools to control this disease complex and influence the spectrum of fungal communities in infected wheat stems. The aim of the present study was to determine the impact of crop rotation schemes and soil tillage methods on the development of WSD and to elucidate the spectrum of causal agents of this disease. The development of WSD was assessed in a two-factorial (soil tillage practice and crop rotation) experiment. The incidence of WSD was evaluated at the BBCH growth stages 83–85. Causal agents of WSD and other fungi were identified using molecular methods. The soil tillage method did not influence the development of WSD, but the impact of crop rotation was significant, and the cropping system where oilseed rape, barley and faba beans were included decreased disease levels. Members of the genera Oculimacula and Fusarium were the most prevalent fungi associated with WSD. Moreover, fungi from other taxonomic groups were detected, with Phaeosphaeria spp. being prevalent. An increasing occurrence of Microdochium spp. was also observed. In conclusion, agronomic practices influenced the level of WSD, but no distinct impact on the fungal spectrum was identified. Further investigation is required to clarify the roles that pathogens and fungi from other taxonomic groups play in the fungal–wheat relationship.

Skuteczność fungicydów w ochronie podstawy źdźbła pszenicy ozimej przed grzybami patogenicznymi

The aim of the experiments was to analyze the effectiveness of fungicides in the protection of stem base of winter wheat against pathogenic fungi. The study was conducted on winter wheat variety Bogatka in 2012–2015. Eight fungicides were used in the experiment. Every year the degree of infection of the stem base with pathogens was evaluated at the growth stage of medium milk, grain content milky (BBCH 75) and the effectiveness of the applied fungicides was assessed as well. The presence of sharp eyespot, eyespot, fusarium stem rot was recorded, except for the year 2012 when no signs of eyespot were observed. The occurrence of symptoms of sharp eyespot was low in the following years (up to 17.7% of infected plants). The fungicides used in the experiment showed different effectiveness in controlling diseases of the wheat stem base. Celem przeprowadzonych doświadczeń była ocena skuteczności zastosowanych fungicydów w ochronie podstawy źdźbła pszenicy ozimej przed grzybami patogenicznymi. Badanie wykonano w latach 2012–2015 na pszenicy ozimej odmiany Bogatka. W doświadczeniu zastosowano osiem fungicydów. Każdego roku w fazie BBCH 75 (pełnej dojrzałości mlecznej ziarniaków) oceniano stopień porażenia podstaw źdźbeł przez patogeny oraz skuteczność działania zastosowanych środków grzybobójczych. Stwierdzono objawy ostrej plamistości oczkowej, łamliwości źdźbła zbóż i traw oraz fuzaryjnej zgorzeli podstawy źdźbła i korzeni, z wyjątkiem 2012 roku kiedy nie zaobserwowano występowania objawów łamliwości źdźbła zbóż i traw. Nasilenie symptomów ostrej plamistości oczkowej było w kolejnych latach niewielkie (maksymalnie 17,7% porażonych źdźbeł). Zastosowane w doświadczeniu fungicydy wykazały zróżnicowaną skuteczność w zwalczaniu chorób podstawy źdźbła pszenicy.

Weather determines the occurrence of wheat stem base diseases in biogas cropping systems

Renewable energy produced at biogas plants has tremendously increased the demand for digestible biomass in central Europe over the last twenty years. As a consequence, new crop rotations combining conventional and recently introduced bioenergy crops are tested in long-term field trials. The aim of this work was to determine risks for soilborne wheat stem base diseases in new bioenergy crop rotations. Crop rotations tested consisted of maize, sorghum, cereals, grasslegume mixtures, and phacelia. Field trials with five rotations were established at four different sites in Germany, whereby winter wheat was grown at the end of each rotation. Field trials were set up in a block or strip plot design in 2005 and 2006. After eight years, stem base diseases of winter wheat were visually assessed during milk ripeness. ‘Random forests’, a non-parametric statistical method, was used to select the most important variables describing weather, soil productivity and rotation. Subsequently, disease incidences were modeled with generalized linear models. Disease incidence was high for Fusarium foot rot (47%), moderately high for eyespot (30%), and low for sharp eyespot (4%). An increasing number of days with high precipitation during six weeks after sowing, and less growing degree days from February through June led to higher eyespot incidence (R2 = 60%). Fusarium foot rot incidence was correlated to high mean precipitation during six weeks after sowing, and low number of growing degree days from February through June (R2 = 78%). In contrast to the eyespot model, year and region had additional explanatory power to the Fusarium foot rot model. Based on the results of this study we could show that annual weather patterns had a high impact on eyespot and Fusarium foot rot incidences, while the effect of rotation was low. Although unexplained site and year-specific effects require further investigations, weather patterns identified by applying an innovative variable selection method provide a valuable starting point for developing and improving forecasting models for Fusarium foot rot.

Development of three fusarium crown rot causal agents and systemic translocation of deoxynivalenol following stem base infection of soft wheat

Fusarium pseudograminearum, F. culmorum and F. graminearum are the most important fusarium crown rot (FCR) causal agents. They have the common ability to biosynthesize deoxynivalenol (DON). To elucidate the behaviour of each of the three species, a comparative study was carried out to investigate symptom progression, fungal systemic growth and translocation of DON following stem base inoculation of soft wheat. FCR symptoms were mainly localized in the inoculated area, which extended up to the second node for all inoculated species. Only the most aggressive strains caused symptoms up to the third node. Real‐time quantitative PCR showed that fungal colonization reached the third node for all the tested species, but a low percentage of plants showed colonization above the third node following inoculation with the most aggressive strains. Fungal growth was detected in symptomless tissues but none of the three species was able to colonize as far as the head tissues. However, even if the pathogens were not detected in the heads, DON was detected in head tissues of the plants inoculated with the most aggressive strains. These results demonstrate that F. pseudograminearum, F. culmorum and F. graminearum, under the same experimental conditions, follow a similar pattern of symptom progression, fungal colonization and DON translocation after stem base infection. Differences in the extent of symptoms, fungal colonization and mycotoxin distribution were mainly attributable to strain aggressiveness. These findings provide comparative information on the events following infection of the stem base of wheat by three of the most important FCR casual agents.

Fusarium Head Blight and Crown Rot on Wheat & Barley: Losses and Health Risks

Crown rot (FCR) caused by many kinds of Fusarium spp as F. pseudograminearum and F. culmorum is a common pathogen to FCR while F. grarnineurm group I, F. crookwellense, F. avenaceum and F. nivale [3-6]. FCR disease infect the stem base of wheat and barley causing necrosis and dry rot of the crown bases always brown, often extending up 2-4 nodes, basal stem and root tissue commonly known as crown rot [7]. Whitehead formation is most severe in seasons with a wet start and dry climates, pinkish fungal growth may form on lower nodes especially during moist weather (Figure 1).

Antagonistic yeasts competes for iron with winter wheat stem base pathogens

Aureobasidium pullulans and Sporobolomyces roseus are a saprotrophic yeasts fungi commonly found on the leaves of winter wheat and on wheat kernels. The objective of this study was to compare the inhibitory effects of two species of yeasts fungi, Aureobasidium pullulans var. pullulans (de Bary) G. Arnaud and Sporobolomyces roseus Kluyver & van Niel, on the causal agents of stem base diseases, Rhizoctonia cerealis v. d. Hoeven, Gaeumannomyces graminis (Sacc.) Arx & D. Olivier, Helgardia herpotrichoides (Fron) Crous & W. Gams, Fusarium oxysporum (Schlecht) Snyd. et Hans.) and Fusarium culmorum (W. G. Smith). A. pullulans showed stronger inhibitory activity than S. roseus. Among the 70 A. pullulans isolates tested in the study, 25 were capable of suppressing the colony growth of R. cerealis under in vitro conditions. This is the first study to show that A. pullulans competes for iron with stem base pathogens, in particular with fast-growing R. cerealis and F. culmorum. Under greenhouse conditions, A. pullulans protected winter wheat seedlings against infection caused by F. culmorum, from two to four times compared with the control, and its protective effect was determined by the infection susceptibility of wheat cultivars and the time interval between the application of A. pullulans and inoculation with F. culmorum.

Fungi communities colonizing the stem base of winter wheat

In the present study species which colonize the stem base of winter wheat and cause different types of diseases were analyzed. It was demonstrated that <i>Fusarium avenaceum, F. culmorum, Pseudocereosporella herpotrichoides</i> and <i>Rhizoetonia cerealis</i> were most of ten isolated from the stem base of winter wheat. It was not always possible to determine the pathogen which was responsible for the specific disease symptoms.

Interactions between fungi colonizing the stem base of winter wheat

<em>In vitro</em> conditions, the interactions betecen the fungi most frequently isolated from the stem base of winter wheat were determined. These were the species from genus <em>Fusarium (F. culmorum, F. avenaceum</em> and<em> F. poae</em>) and <em>Rhizoctonia cerealis, Pseudocercosporella herpotrichoides, Alternaria alternata</em> and <em>Aureobasidium bolleyi</em>. Some saprotrophes showed stimulating effect on <em>R. cerealis, P. herpotrichoides</em> and F. poae. Certain species in combined cultures showed exceptionally favourable relationships.

Early PCR-based detection of Fusarium culmorum, F. graminearum, F. sporotrichioides and F. poae on stem bases of winter wheat throughout Poland

Foot rot and crown rot are fungal diseases of wheat caused by a complex of Fusarium species. They have a huge economic impact mainly due to yield reduction. A survey was conducted to identify four Fusarium species, occurring on wheat stem bases, using species-specific PCR assays in samples collected during spring of 2012. The dominant species was F. graminearum, which was identified in above 64 % of samples. F. culmorum was detected in 15.71 %, F. poae in 15.71 % and F. sporotrichioides in 5.71 % wheat fields. Most of the wheat fields in the eastern Poland were infected with at least one or two of Fusarium species, while in central Poland no Fusarium species were identified in most of the fields. The presence of F. graminearum tends to favor the presence of F. culmorum and this effect was visible also for F. poae and F. sporotrichioides. The frequency of F. graminearum and F. culmorum detections were highest where wheat crops were preceded by maize and in the samples from late sown fields. The opposite observation was made for F. poae and F. sporotrichioides, where the number of detections of these species was higher in samples from early sown fields. The number of detected Fusarium species was significantly lower in samples collected from fields protected with autumn herbicide in comparison to unprotected fields. The rate of autumn N fertilization did not affect the number of Fusarium detections.

Mapping resistance genes for Oculimacula acuformis in Aegilops longissima.

This study identified three QTL conferring resistance to Oculimacula acuformis in Aegilops longissima and their associated markers, which can be useful in marker-assisted selection breeding for eyespot resistance. Oculimacula acuformis is one of two species of soilborne fungi that cause eyespot of wheat, the other being Oculimacula yallundae. Both pathogens can coexist in the same field and produce elliptical lesions on stem bases of wheat that are indistinguishable. Pch1 and Pch2 are the only two eyespot resistance genes readily available to wheat breeders, but neither provides complete control. A new source of eyespot resistance was identified from Aegilops longissima (2n = 14, S(l)S(l)), a wild relative of wheat. Three QTL for resistance to O. acuformis were mapped in chromosomes 1S(l), 3S(l), and 5S(l) using a recombinant inbred line population developed from the cross Ae. longissima accessions PI 542196 (R) × PI 330486 (S). The three QTL explained 66 % of phenotypic variation by β-glucuronidase score (GUS) and 84 % by visual rating. These QTL had LOD values of 10.6, 8.8, and 6.0 for GUS score, and 16.0, 10.0, and 13.0 for visual rating. QTL associated with resistance to O. acuformis have similar chromosomal locations as some for resistance to O. yallundae, except that a QTL for resistance to O. yallundae was found in chromosome 7S(l) but not for O. acuformis. Thus, it appears that some genes at the same locus in Ae. longissima may control resistance to both eyespot pathogens. QTL effective against both pathogens will be most useful for breeding programs and have potential to improve the effectiveness and genetic diversity of eyespot resistance.

Ocena przydatności biostymulatorów i międzyplonu w redukcji występowania chorób podsuszkowych w krótkotrwałej monokulturze pszenicy jarej

The field research was conducted at theAgriculturalAdvisoryCenterin Łosiów (opolskie providence) in 2011–2012. The objective of the experiment was the assessment of the effectiveness of the use of bio‐stimulators and ploughing down stubble crop to reduce the infection of spring wheat stem base and its roots by pathogens occurrence. It was established that ploughing down stubble crop of phacelia as well as the use of bio‐stimulators did not significantly affect the infection of roots and stems of spring wheat grown in monoculture. The continuous crop of spring wheat instead of environmentally correct crop succession increased of roots and stem base diseases. Badania polowe przeprowadzono w Opolskim Ośrodku Doradztwa Rolniczego w Łosiowie, w latach 2011–2012. Celem przeprowadzonego doświadczenia była ocena skuteczności stosowania biostymulatorów oraz przyorywania międzyplonu ścierniskowego w ograniczaniu porażania podstawy źdźbła i systemu korzeniowego pszenicy jarej przez patogeny wywołujące choroby podsuszkowe. Wykazano, że przyorywanie międzyplonu ścierniskowego z facelii błękitnej oraz zastosowanie biostymulatorów nie miało istotnego wpływu na porażenie korzeni i źdźbeł pszenicy jarej uprawianej w monokulturze. Z kolei zrezygnowanie z przyrodniczo poprawnego następstwa roślin na rzecz uprawy monokulturowej przyczyniło się do zwiększenia porażenia źdźbeł przez patogeny wywołujące choroby podstawy źdźbła.

Root and Foot Rot Diseases of Winter Wheat Grown in Conventional and Organic Systems

The object of the study was fungous diseases occurring on roots, leave sheaths and stem base of winter wheat in the two opposing cropping systems (organic and conventional). The observations were made in vegetation periods (2007-2009) in the fields of winter wheat in northern Poland. Every year on each plot of compared farming systems root rot occurred (Fusarium spp., Gaeumannomyces graminis and other fungi). For the period of 3 years the degree of disease injury on the roots of winter wheat grown in the conventional system in the vegetation period increased, while in the organic one remained on pretty the same level. On average a lot more affected roots, especially in the flowering stage, occurred on the winter wheat grown in the conventional system. Fusarium foot rot (Fusarium spp.) developed on the wheat during the entire vegetation period. It was the most dangerous root and foot rot disease (the highest indexes of injury). The mean degree of disease injury on leave sheath was on pretty the same level in the two farming systems, although in investigated vegetation periods differed a lot, whereas at the bases of stems the pathogen was on the higher level on the wheat in the conventional system. Also eyespot (Tapesia yallude) developed in the entire vegetation period of the winter wheat, but its intensity was much lower than in case of fusarium foot rot. Leave sheaths of the wheat grown in the conventional system were slightly stronger affected than those grown in the organic system. In the flowering stage the intensity of the disease in both farming systems became equal, while in the wax maturity it was considerably higher in the conventional system. Sharp eyespot (Rhizoctonia spp.) appeared relatively late and occurred only in two years of investigation. The intensiveness of the disease was definitely higher on the organic plots. Among the affected roots, taken in the stem elongation stage, from the organic system 28 cultures of fungi were isolated, and from the conventional one 24 colonies. Cereals pathogenic fungi amounted 35.8% of isolates obtained from the organic system and as many as 66.7% from the conventional system. Among the affected roots, taken in the flowering stage, from the organic system 68 cultures of fungi were isolated in all, and from the conventional one 25 colonies. Cereals pathogenic fungi amounted 38.2% of isolates obtained from the organic system and 56.0% from the conventional system. Among the affected stem bases, taken in the wax maturity stage, from the organic system 56 cultures of fungi were isolated in all, and from the conventional one 52 colonies. Cereals pathogenic fungi amounted 48.4% of isolates obtained from the organic system and 53.6% from the conventional system. In the case of all root and foot rot diseases of wheat grown in the organic system, an advantageous influence of greater biodiversity and number of various fungi species living in root proximity was noticed as opposed to the conventional system.

Cropping systems with maize and oilseed rape for energy production may reduce the risk of stem base diseases in wheat

Cropping systems with crops cultivated in short cycles on the same land provoke phytosanitary problems which may force more chemical inputs. However, the potential effects of cropping systems with emphasis on energy crops, i.e. maize and oilseed rape on the incidence and severity of stem base and root diseases of wheat have not been investigated thoroughly. We therefore analyzed the effects of varied percentages of maize and oilseed rape on stem base and root pathogens of winter wheat grown in four different cropping systems and rotations in two locations in Central and Northeastern Germany for three years. Our results demonstrate that short and intensive crop rotations with wheat combined with crops for bioenergy production do not necessarily enhance the risk by soil and straw borne diseases. Moreover, a suitable combination of wheat, oilseed rape and maize with adapted cropping methods (late sowing after maize, ploughing) can significantly mitigate the threat of stem base diseases in wheat. While disease incidence of sharp eyespot was always <5%, cropping systems had significant effects on the incidence and severity of eyespot, fusarium foot rot and take-all (in Northeastern Germany). Incidence of fusarium foot rot and take-all was significantly reduced by 70% and incidence of eyespot nearly to 0%, when wheat was planted after maize in a system with late sowing and ploughing, compared to wheat after oilseed rape with reduced tillage and early sowing. Further, these cropping systems with maize showed a low level of fusarium head blight. DON levels in grains were always low. The present study demonstrates that current shifts in crop rotations to a higher prevalence of maize due to novel market developments do not necessarily enhance the phytosanitary risks in the main crop wheat, if a suitable system of agronomic measures is applied, enabling highly productive and sustainable energy crop production systems.