Sharp eyespot caused by Rhizoctonia cerealis was assessed in four winter wheat crops surveyed at four locations in north-central Poland in [2006][2007][2008][2009]. At the four locations symptoms developed on 41.9-67.7 % of shoots of all plants (average of 4 years) and on 49-73.5 % of shoots of diseased plants (average of 4 years). Slight (category 1) disease was most frequent, occurring on 24.4-41.3 % of shoots (range 14.8-51.3 %); moderate (category 2) disease was less frequent, occurring on 16.9-25.5 % of shoots (range 8.9-32.4 %); severe (category 3) disease was least frequent, occurring on 3.2-7.1 % (range 0-22.0 %) of shoots. Sharp eyespot affected wheat growth and yield, and grain quality. Disease, especially in the severe category, was associated with significant decreases in plant and ear dry weights, number of grains per ear, grain dry weight per ear and thousand-grain weight, and with increases in grain protein and wet gluten contents, Hagberg falling number and sedimentation value. There was an association between occurrence of sharp eyespot in stems and colonization of grain by fungi. Alternaria alternata and E. nigrum were the most common species.

The plant semiochemical cis-jasmone primes/induces plant resistance that deters herbivores and attracts natural enemies. We studied the induction of volatile organic compounds (VOCs) in winter wheat and spring barley after exposure of plants to three synthetic cis-jasmone doses (50 μl of 1, 100, and 1 × 10(4) ng μl(-1)) and durations of exposure (1, 3, and 6 h). Cereal leaf beetle, Oulema melanopus, adult behavioral responses were examined in a Y-tube olfactometer to cis-jasmone induced plant VOC bouquets and to two synthetic blends of VOCs (3 green leaf volatiles (GLVs); 4 terpenes + indole). In both cereals, eight VOCs [(Z)-3-hexanal, (Z)-3-hexanol, (Z)-3-hexanyl acetate, (Z)-β-ocimene, linalool, β-caryophyllene, (E)-ß-farnesene, and indole] were induced 100- to 1000-fold after cis-jasmone exposure. The degree of induction in both cereals was usually positively and linearly associated with increasing exposure dose and duration. However, VOC emission rate was only ~2-fold greater from plants exposed to the highest vs. lowest cis-jasmone exposure doses (1 × 10(4) difference) or durations (6-fold difference). Male and female O. melanopus were deterred by both cereal VOC bouquets after plant exposure to the high cis-jasmone dose (1 × 10(4) ng μl(-1)), while females were also deterred after plant exposure to the low dose (1 ng μl(-1)) but attracted to unexposed plant VOC bouquets. Both O. melanopus sexes were repelled by terpene/indole and GLV blends at two concentrations (25 ng · min(-1); 125 ng · min(-1)), but attracted to the lowest dose (1 ng · min(-1)) of a GLV blend. It is possible that the biologically relevant low cis-jasmone dose has ecological activity and potential for inducing field crop VOCs to deter O. melanopus.

No abstract

We investigated incidences of Fusarium head blight (FHB) and concentrations of six mycotoxins (deoxynivalenol, nivalenol, 3-acetyldeoxynivalenol, T-2 toxin, HT-2 toxin and zearalenone) in wheat from 2010 to 2013. Field trials were conducted at the Experimental Station of Cultivar Testing in Chrząstowo, Poland (53 o 11'N, 17 o 35'E). We examined the effects of four agronomic factors, including pre-crop type (corn, sugar beets and wheat), date of sowing (late autumn: November 8-December 9 or spring: March 29-April 19), fungicidal application (untreated or treated with two applications) and cultivar (Monsun, Cytra), on FHB index (FHBi) and mycotoxin levels in order to minimize the risk of wheat grain contamination by mycotoxins via integrated pest management methods. The dominant Fusarium species observed on wheat heads were F. culmorum, F. avenaceum (Gibberella avenacea) and F. graminearum (Gibberella zeae), at 21.1%, 17.2% and 7.1%, respectively. A monthly rainfall sum of 113.9 mm and a relatively low air temperature (monthly average 15.5°C) resulted in the highest FHBi in untreated wheat (25.1%). Agronomic factors crucial for the FHB incidence were the pre-crop, fungicidal treatments and cultivar selection. In wheat planted after wheat or corn, the FHBi was higher compared with a precrop of sugar beet. A double application of fungicides at BBCH 30-32 with prothioconazole and spiroxamine and at a BBCH 65 with fluoxastrobin and prothioconazole effectively reduced the FHBi and mycotoxin concentrations, respectively, in grain. The cultivar 'Cytra' had a greater FHBi (10.4%) than 'Monsun' (4.6%), and grain infestations by Fusarium species were also greater in 'Cytra', at 16.5%, than in 'Monsun', at 11.2%. Untreated cv. Cytra grown after corn in spring produced grains with the highest amounts of the mycotoxins, deoxynivalenol, 103, 17.5 and 5.53 μg/kg, respectively). Total mycotoxin levels in wheat were correlated with five determinants: duration of the period between the end of flowering and the beginning of kernel abscission, FHBi, F. culmorum isolation, G. zeae isolation and Fusarium ratio (FR) as a % of total mould isolations. Although, the mean concentration of mycotoxins in grain did not exceed the maximum permissible values for unprocessed wheat our study suggests necessity to monitor and mitigate FHB risk for susceptible cultivars, when wheat spring sowing follows corn or wheat.

Abstract:Winter cereals (wheat, triticale, rye, barley) grown in experimental fields were assessed for sharp eyespot. Preceding crops (spring cereals and fallow) and weed control (herbicides application, no control) were taken into account. The health status evaluation was carried out at the stem elongation phase and at the milk maturity stage. The macroscopic estimation was accompanied by the analysis of fungal species identified on stem bases and roots, which showed various disease symptoms. The analysis of fungal species from the genus Rhizoctonia were especially noted. Mycological analysis of roots was carried out at the seedling growth and stem elongation phase, and stem bases at the seedling growth and milk maturity stage. Infection caused by Rhizoctonia spp. was confirmed by polymeraze chain reaction (PCR) assay. The highest infection was noted on wheat followed by triticale, rye and barley.Occurrence of sharp eyespot depended more on weed control than on what the preceding crop had been. At the milk maturity stage, lower severity of sharp eyespot of triticale, rye and barley was noted on plots not treated with herbicides, and on wheat with herbicide application. The research showed a significant effect of the preceding crop only on the health status of wheat. At the milk maturity stage, the highest infection was noted after spring triticale and the lowest after oats. Stems of cereals with sharp eyespot symptoms and healthy stems were settled mainly by Rhizoctonia cerealis (wheat -25.6%, triticale -12.0%, rye -22.2%, barley -11.3%), rarely by R. solani (respectively 6.0, 4.0, 2.9 and 1.8%). Rhizoctonia solani was isolated more often from roots with true eyespot and Fusarium foot rot symptoms. It may suggest that R. cerealis was the main causal agent of sharp eyespot on all tested cereals. The preceding crop did not affect the composition of Rhizoctonia species.

Crop management should be determined to reintroduce ancient wheat. This study aimed to determine: i. the response of the yield of ancient wheat on sowing density; ii. the impact of sowing density on plant health, weed infestation and pest occurrence. Field experiments were carried out in Poland, on three organic farms. The factors were: (1) wheat species: Persian wheat (Triticum persicum Vav.) and Indian dwarf wheat (T. sphaerococcum Perc.), (2) sowing density (400, 500, and 600 grains m−2). Increasing the sowing density of T. sphaerococcum from 400 to 600 grains m−2 increases the grain yield and reduces the pest pressure (Oulema spp. and Aphididae). Sowing densities did not affect the severity of powdery mildew at stem elongation as well as root rot and eyespot at the development of fruit. At the highest sowing density, the leaf area with tan spot symptoms was the highest. The eyespot symptoms occurred more frequently and the damaged plant surface caused by Oulema spp. was larger on T. sphaerococcum. Persian wheat turned out to be more susceptible to weed infestation. Indian dwarf wheat and Persian wheat are useful for organic farming, and the sowing density should be 500 or 600 grains m−2 and 400 grains m−2, respectively.

Occurrence of sharp eyespot was determined in the period 2006-2008, on commercial fields of spring cereals, localized in northern and central Poland. Percent of infected stems, and the disease index were evaluated. Occurrence of sharp eyespot on spring cereals, especially on oat, was low. Slight infection was mostly observed. In some farm fields, disease symptoms were not observed.A significant difference in the occurrence of sharp eyespot on barley in respective years was noted. On commercial farms, the effect of previous crop and fungicidal treatment on occurrence of sharp eyespot was not observed. Significant variation of the infection was noted only for barley. Presence of Rhizoctonia cerealis and R. solani in the damaged tissues was confirmed by mycological analysis as well as PCR assay.

Effects of agronomic practices on the occurrence of sharp eyespot and Rhizoctonia spp. in winter wheat were determined in two field experiments. In Experiment 1, in the village of Osiny, a comparison was made of disease in different farming systems. The farming systems were: organic, integrated, conventional, and monoculture. In Experiment 2, in the village of Mochełek, the effects of different chemical controls (no treatment, herbicide, herbicide + fungicide), mineral fertilizer doses (147 and 221 kg/ha NPK) and sowing densities (400 and 600 grains/m2) on the occurrence of sharp eyespot were compared in wheat grown in short-term monoculture. There was considerably more sharp eyespot in 2007 (disease index 1.63-29.5%) than in other years. Significant effects of the treatments were mostly noted at the milk ripe growth stage. The fewest sharp eyespot symptoms were seen in the integrated farming system. The most sharp eyespot symptoms were seen in the conventional and organic systems. There was a tendency for an increased intensity of symptoms in successive wheat-growing years of short-term monoculture. The application of pesticides showed no clear effect on the occurrence of sharp eyespot. The herbicide resulted in increased or decreased disease intensity depending on the cultivation year and the date of observation. Fungicide application did not decrease infection. Without chemical control, more symptoms were observed at the lower NPK rate. There were more symptoms at the higher sowing density. Stems with sharp eyespot symptoms were mostly infected by Rhizoctonia cerealis, and less frequently by R. solani. Binucleate Rhizoctonia spp., which could not be identified to species using polymerase chain reaction (PCR) techniques, were also recorded. Two R. zeae isolates were also obtained from stems with disease symptoms in Mochełek. R. solani was more often isolated from roots or stems with symptoms of true eyespot or fusarium foot rot. Most isolates of Rhizoctonia spp. were obtained at the milk ripe stage. A wheat-growing system and chemical control did not greatly affect the frequency of Rhizoctonia spp.