Powdery mildew (Blumeria graminis f. sp. tritici) is one of the most devastating wheat diseases. The wheat line N9134 contains PmAS846 that was transferred to N9134 from wild emmer wheat, and is still one of the most effective resistance genes in China. A full-length wheat RPM1 gene was obtained by rapid amplification of cDNA ends (RACE) based on the up-regulated probe sequence from differentially expressed transcripts during the N9134 and powdery mildew interaction. The gene was named TaRPM1, and the open reading frame (ORF) is 2721 nucleotides and encodes a polypeptide of 907 amino acids with a predicted isoelectric point of 4.86. Phylogenetic analysis revealed that TaRPM1 was highly homologous on both Aegilops tauschii and Triticum urartu at both the nucleotide and protein level. Using real-time quantitative PCR, the TaRPM1 gene expression level in wheat leaves was found to be sharply up-regulated, while the transcript level was lowly induced in the root and stem. Under the powdery mildew treatment, the transcription profile of TaRPM1 was very strongly expressed at 48 hour post inoculation (hpi), which increased again to 96 hpi and reaching a high level at 120 hpi. Based on sequence similarities and positions, we inferred that the TaRPM1 gene was on wheat chromosome 3D. These results suggested that TaRPM1 plays an important role in the mechanism of innate immunity to infection by the powdery mildew pathogen.
Authors:J.H. Czembor, A. Pietrusińska, U. Piechota, and D. Mańkowski
Barley recombinant lines obtained from crosses and backcrosses of common barley (Hordeum vulgare L.) cultivars Emir and Golden Promise with bulbosus barley grass (H. bulbosum L.) were tested against differential set of 14 Blumeria graminis D.C. Golovin ex Speer f. sp. hordei – synamorph Erysiphe graminis DC. f. sp. hordei Em Marchall isolates, pathogenic fungus causing powdery mildew. Powdery mildew resistance was found in 22 from 24 lines tested. Presence of unknown genes was postulated in 13 lines. In six of these lines the unknown genes were postulated present besides Mla12 allele originated from H. vulgare parent (cv. Emir). The only line resistant to infection, from all isolates used, was 181P94/1/3/1/1/1-2. Four other lines could be considered highly resistant, because they were susceptible to only one powdery mildew isolate. The possibilities to use the hybrid lines with identified resistance to powdery mildew, especially line 181P94/1/3/1/1/1-2 in barley breeding programs were discussed.
Authors:S. Tonti, G. Alvisi, A. Pisi, P. Nipoti, and A. Prodi
Zymoseptoria tritici, a globally distributed pathogen, is responsible of Septoria tritici blotch (STB), one of the most damaging wheat diseases. In Italy the incidence of STB has increased during the past few years. The presence of Z. tritici on flag leaves of susceptible durum wheat plants, cultivar San Carlo, after a single artificial inoculation with two inoculum concentrations at different vegetative stages has been evaluated in the plain of Bologna (North of Italy), in a two year field study (2012–2013). The pathogen presence was also assessed in natural infection conditions after a fungicide application in the second year (2013). The results obtained, by visual examination (Incidence, Disease Severity) and DNA quantification by Real time PCR, demonstrated that BBCH 39 (flag leaf stage) is the most susceptible vegetative stage, independently of inoculum concentration and climatic conditions. A good correlation between Disease Severity and DNA quantity was observed in either sampling methods, entire flag leaves and flag leaf discs. Thereafter the most suitable period to obtain the best crop protection with only one fungicide treatment is the flag leaf stage.
Authors:F. Vučajnk, S. Trdan, G. Leskošek, I.J. Košir, A. Sreš, D. Kocjan Ačko, and M. Vidrih
In 2014 and 2015, we studied the effect of fungicide spraying with 11 different nozzles on the quality and quantity of head and leaf fungicide deposit, the percentage of Fusarium head blight (FHB) incidence, FHB index, the DON content, yield and grain quality parameters. The best quality and quantity of fungicide deposit on the front and rear head sides was achieved with the TeeJet Turbo FloodJet TF VP2 nozzle (FLOOD) and the Albuz AVI-TWIN 110-03 nozzle (AVI). In comparison with the majority of treatments, the FHB incidence and the FHB index was the highest on the unsprayed control. The FHB index was higher using the Lechler IDK 120-03 nozzle (IDK) than with the other nozzle types. In all the treatments, the DON content in the grain was less than 50 μg/kg. At this very low level of infection this is not surprising. The grain yield was the smallest on the unsprayed control. Better fungicide coverage of wheat heads with the FLOOD and AVI nozzles did not result in a statistically higher yield or better grain quality parameters. Negative correlations were confirmed between yield and variables as DON content, FHB incidence and FHB index and also between falling number and variables as fungicide coverage, FHB incidence and FHB index. Positive correlations were determined between DON content and FHB incidence, between hectolitre weight and variables as spray deposit and coverage and between protein content and variables as spray deposit and coverage.
Authors:M. I. E. Arabi, E. Al-Shehadah, and M. Jawhar
Cochliobolus sativus, the causal agent of common root rot (CRR), is a devastating fungal pathogen of barley that can cause significant yield losses worldwide. The development of resistant cultivars has proven difficult, therefore, in this work, CRR-resistant barley germplasm was developed by crossing three resistant-by-susceptible cultivars currently used in Europe and West Asia. Following greenhouse evaluations of 150 doubled haploid lines derived from these crosses, 40 lines were evaluated under artificial infection conditions using incidence and severity parameters during two consecutive seasons. Data showed significant differences among barley lines with a continuum of resistance levels ranging from highly susceptible to resistant which were consistent in both seasons. However, five promising lines had slightly lower CRR disease than the others. Additionally, significant differences (P <0.05) in mean incidence and severity values were found among lines, with values being consistently higher in the susceptible ones. However, CRR severity increased linearly as incidence increased in both seasons. All together, the present study suggests that, the newly identified resistance lines can serve as potential donors for ongoing CRR resistance breeding program to generate high-yielding commercial barley cultivars, and that the positive correlation between CRR parameters I and S may be beneficial for many types of studies on this disease.
Authors:Y.-E. Chen, S. Jin, Q.-S. Zhao, Y. Zhang, and C.-L. Wang
Lipopolysaccharide and b-1,3-glucan binding protein (LGBP) is a pattern recognition receptor that can recognize and bind LPS and b-1,3-glucan. LGBP has crucial roles in innate immune defense against Gram-negative bacteria and fungi. In this study, LGBP functions in Portunus trituberculatus innate immunity were analyzed. First, the mRNA expression of PtLGBP in hemocytes, hepatopancreas, and muscle toward three typical pathogen-associated molecular patterns (PAMPs) stimulations were examined using real-time PCR. Results show that the overall trend of relative expressions of the LGBP gene in three tissues is consistent, showing up-down trend. In each group, the highest expression of the LGBP gene was at 3 and 12 h post-injection. The LGBP gene is also expressed significantly higher in the hemocytes and hepatopancreas than in the muscle. The highest level of LGBP was in the lipopolysaccharides (LPS) and glucan-injected group, whereas the lowest level was in the PGN-injected group. Furthermore, bacterial agglutination assay with polyclonal antibody specifically for PtLGBP proved that the recombinant PtLGBP (designated as rPtLGBP) could exhibit obvious agglutination activity toward Gram-negative bacteria Escherichia coli, Vibrio parahaemolyticus, and V. alginolyticus; Gram-positive bacteria Bacillus subtilis; and fungi Saccharomyces cerevisiae. LGBP in Portunus trituberculatus possibly served as a multi-functional PRR. In addition, LGBP is not only involved in the immune response against Gram-negative and fungi, as manifested in other invertebrates, but also has a significant role in anti-Gram-positive bacteria infection.
Authors:Rita Bán, Gellért Baglyas, Ferenc Virányi, Balázs Barna, Katalin Posta, József Kiss, and Katalin Körösi
White rot caused by Sclerotinia sclerotiorum (SS) is one of the most devastating plant diseases of sunflower. Controlling this pathogen by available tools hardly result in acceptable control. The aim of this study was to elucidate the effects of plant resistance inducers, BTH (benzothiadiazole in Bion 50 WG) and arbuscular mycorrhizal fungi (AMF) on disease development of white rot in three sunflower genotypes. Defence responses were characterized by measuring the disease severity and identifying cellular/histological reactions (e.g. autofluorescence) of host plants upon infection. Depending on the host genotype, a single application of inducers reduced disease symptoms. Histological examination of host responses revealed that BTH and/or AMF pre-treatments significantly impeded the development of pathogenic hyphae in Iregi szürke csíkos and P63LE13 sunflower plants and it was associated with intensive autofluorescence of cells. Both localized and systemic induction of resistance was observed. Importantly, the frequency of mycorrhization of hybrid P63LE13 and PR64H41 was significantly increased upon BTH treatment, so it had a positive effect on the formation of plant-mycorrhiza interactions in sunflower. To our knowledge, this is the first report on the additive effect of BTH on mycorrhization and the positive effect of these inducers against SS in sunflower.
Authors:Banu Kaskatepe, Serap Suzuk Yildiz, Merve Eylul Kiymaci, Ayse Nur Yazgan, Salih Cesur, and Sinem Aslan Erdem
In recent years rapidly growing antibiotic resistance has increased interest toward natural products, especially essential oils because of their various effects. The aim of this study was to identify the chemical composition of the commercial Origanum onites essential oil (EO) and to investigate the antimicrobial activity by disc diffusion and dilution methods, against ten different ATCC strains, including eight bacteria, two yeasts and seventy-nine clinical nosocomial Escherichia coli isolates that produce extended spectrum beta lactamase (ESBL). The chemical composition of EO was analyzed by GC and GC-MS. The major compounds of the EO were determined as carvacrol (51.4%) followed by linalool (11.2%), p-cymene (8.9%) and γ-terpinene (6.7%). O. onites EO had antimicrobial activity against all standard strains and inhibited microbial growth of ESBL positive E. coli isolates. According to our results, O. onites EO may be an alternative to synthetic drug, used in combination with other antibiotics for treatment of infection caused by multidrug resistant bacteria after testing toxic effects and irritation at preferred doses on human.
The downside of plant tissue culture techniques is an unwanted microbial contamination. Elimination of contaminants is the first step of any successful investigation on plant tissue culture. Preliminary experiments on Araucaria excelsa R. Br. var. glauca (Norfolk-Island pine) (syn.: A. heterophylla) showed that most common decontaminants could not successfully eliminate the contamination. Therefore, nano silver (NS) colloids were evaluated for controlling contamination. Treatments were included soaking the explants in NS solution or adding NS to the culture medium. Explants were cultured on MS medium supplemented with appropriate growth regulators for their establishment. Results showed that surface sterilization followed by treatment with 200 mg l−1 of NS with soaking time of 180 min reduced the bacterial contamination from 61.5% to 11.3% and adding 400 mg l−1 NS to the medium reduced the bacterial contamination from 81.25% to 18.75%. Nano silver could be applied without adverse effects on plant growth and development. This is the first report on in vitro establishment of A. excelsa R. Br. using NS to reduce bacterial infections.
Authors:M. Kwiatek, H. Wiśniewska, Z. Kaczmarek, M. Korbas, M. Gawłowska, M. Majka, K. Pankiewicz, J. Danielewicz, and J. Belter
Pch1 gene translocated from Aegilops ventricosa provides effective resistance to eyespot in wheat. To track the Pch1 gene introgression, we investigated 372 genotypes obtained from various breeding programs using endopeptidase EpD1b marker, sequence-tagged-site (STS) marker XustSSR2001-7DL, and the score of infection index (K-index) evaluated after in vivo inoculation test. These genotypes were divided into three groups with 136, 124 and 112 genotypes for the field test lasting three years. In 2011, the mean K-index was 0.81, while 2012 and 2013 the mean K-indexes were 1.60 and 1.46, respectively. Both marker results indicated that 18 genotypes possessed Pch1 gene. Statistical analysis of the level of K-index showed that these 18 genotypes were resistant to eyespot, which verified the proper assignment of wheat genotypes with Pch1 gene based on the marker data. Thus, the endopeptidase and XustSSR2001-7DL are useful for identifying sources of eyespot resistance gene Pch1 in wheat breeding program.