Abstract:Fusarium Head Blight (FHB) is a destructive disease that affects the grain yield and quality of cereals. The relationship between the natural defense chemicals benzoxazinoids and the FHB resistance of field grown winter wheat varieties was investigated. FHB resistance was assessed by the inoculation of wheat ears with mixtures of Fusarium avenaceum, Fusarium culmorum, Fusarium graminearum, and Microdochium nivale. The benzoxazinoids detected in the highest concentration were 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (3.7–9.4 μmol/kg DW) and 2-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (HMBOA, 2.0–11 μmol/kg DW). The cultivars most susceptible to FHB were cvs. Hanseat, Asketis, and Ritmo, while cvs. Petrus, Terra, and Hattrick showed high resistance. 2-O-β-d-Glucopyranosyloxy-4,7-dimethoxy-(2H)-1,4-benzoxazin-3(4H)-one (HDMBOA-glc) and 2-O-β-d-glucopyranosyloxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (HMBOA-glc) were detected. HMBOA-glc was found in higher concentrations than 2-O-β-d-glucopyranosyloxy-2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA-glc). Principal component analyses demonstrated correlation between the susceptibility to FHB and the concentrations of DIMBOA-glc, HMBOA-glc, HMBOA, 2-O-β-d-glucopyranosyloxy-4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one (DIBOA-glc), 2-O-β-d-glucopyranosyloxy-1,4-benzoxazin-3(4H)-one, and 2-O-β-d-glucopyranosyloxy-4-dihydroxy-(2H)-7,8-dimethoxy-1,4-benzoxazin-3(4H)-one (DIM2BOA-glc).
Abstract:Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (Sacc.) W.C. Synder & H.N. Hans is the major limiting factor in the production of tomato. An effort was made to develop an eco-friendly approach to control Fusarium wilt in tomato using fluorescent Pseudomonas, Trichoderma harzianum and Glomus intraradices, an arbuscular mycorrhizal fungus (AMF). Besides direct interaction with plant pathogens, bioagents have been reported to induce systemic resistance in plants. In the present study, a large number of Trichoderma sp. and pseudomonad isolates were evaluated for their efficacy to control Fusarium wilt of tomato. Trichoderma harzianum was multiplied on six different substrates out of which Jhangora, an undertilized grain crop, proved to be the superior substrate. Application of Trichoderma harzianum and fluorescent Pseudomonas by seed biopriming significantly increased seed germination (22-48%) and reduced the days required for germination (2.0-2.5 days). All bioagents used in this study significantly reduced the incidence of wilt in pot and field trials and combinations of bioagents were more effective than single isolate treatments. The combination of fluorescent Pseudomonas, Trichoderma harzianum and AMF provided significantly better control than uninoculated treatment, reducing disease incidence and severity by 74 and 67% in pots and field, respectively. The combination treatments also increased yield by 20%. Addition of cow dung compost (CDC) further reduced disease and improved yield in all treatments. Comparing to control (-CDC), the combination of all three bioagents with CDC significantly reduced disease by 81 and 74% in pots and field, respectively and enhanced the yield by 33%.
Abstract: Jewel sweetpotato storage roots previously treated with a low hormetic dose of ultraviolet light-C (UV-C) were stored for 30 days before inoculated artificially with Fusarium solani,/i>. Storage roots showed an increase in resistance to Fusarium root rot, as indicated by a reduction in lesion diameter, depth and weight of rotted tissue following UV-C treatment. The rate of decay development around F. solani inoculum plugs on UV-C treated sweetpotato storage roots progressed slowly, and about 55% failed to develop lesions on wounded UV-C treated, compared to 11% of untreated sweetpotato storage roots, 10 days after inoculation. There was a polynomial curvilinear regression relationship between percent incidence of Fusarium root rot and hormetic UV-C doses. The hormetic dose of UV-C which suppressed decay to the greatest degree was 3.6 kJ m−2. Exposure of sweetpotato storage roots to doses of UV-C promoted phenylalanine ammonia-lyase (PAL) production with the maximum PAL activity occurred to the greatest degree at a UV-C dose of 3.6 kJ m−2. Similarly, a relationship between PAL activity and the incidence of Fusarium root rot was established. Crude extracts from UV-C treated sweetpotato storage roots reduced germination, germ tube elongation, and growth of F. solani compared to extracts obtained from untreated storage roots.
Abstract: A new 2-arylbenzofuran, 2-(2-methoxy-4,5-methylenedioxyphenyl)-6-hydroxybenzofuran (cicer-furan) has been isolated from roots of the wild chickpea Cicer bijugum by preparative HPLC. The structure was determined by one and two dimensional 1H and 13C NMR spectroscopy and Fast Atom Bombardment-Mass Spectrometry. The concentration of cicerfuran and a previously identified isoflav-3-ene, judaicin, was found to be greater in the roots of plants grown in the presence of the wilt pathogen Fusarium oxysporum f.sp. ciceri than in those grown in wilt-free soil. In addition, both cicerfuran and judaicin inhibited germination of the fungal spores when tested at natural concentrations. Cicerfuran was more potent than both maackiain and medicarpin, which are known antifungal phytoalexins in Cicer. The potential value of cicerfuran as a novel natural defence mechanism for the cultivated chickpea C. arietinum is discussed.
Abstract: The effects of chitosan treatment and inoculation on dry rot in tubers and slices of potato were studied. The results showed that chitosan treatment significantly reduced the lesion diameter of potato inoculated with Fusarium sulphureum. The treatment at 0.25% showed the best effect. Chitosan at 0.25% increased the activities of peroxidase and polyphenoloxidase, and the contents of flavonoid compounds and lignin in tissues. Increased activities of b-1,3-glucanase, and phenylalanine ammonialyase were observed, but there were no significant differences between the treated and the control. These findings suggested that the effects of chitosan could be associated with the induced resistance against Fusarium dry rot in potato.
Abstract: Marker assisted selection (MAS) of resistant varieties is a reliable and faster method of selecting the right varieties for cultivation. The aim of the present study is to find the genes responsible for resistance in highly resistant varieties. In the present work we report the presence of a Resistance (R) gene of CC–NBS–LRR class of plant resistance genes. Both direct PCR amplification from genomic DNA as well as cDNAs, yielded a 0.6 kb DNA sequence indicating the absence of an intron. Sequence analysis of the PCR amplicon obtained from the genomic DNA showed very high homology to R-genes. An interesting observation from the present study is the presence of the R-gene in only resistant varieties. Neither the partially resistant or susceptible varieties showed the presence of this gene sequence. This in turn raises interesting questions on the evolution of these ginger varieties. The cloned R-genes provide a new resource of molecular markers for rapid identification of fusarium yellows resistant ginger varieties.
Abstract:Fusarium head blight (FHB), caused by Gibberella zeae (Schw.) Petch, is a serious disease in many wheat (Triticum aestivum L.) growing regions worldwide. To study the inheritance of FHB resistance against fungal penetration (type I resistance), an Immortalized F2(IF) population containing 198 lines was constructed by crossing recombinant inbred lines chosen with random permutation of 132 RILs. The 132 RILs were chosen from the RIL population derived from the cross between FHB-susceptible cultivar Nanda 2419 and FHB-resistant cultivar Wangshuibai. The population was then evaluated for the percentage of infected spikes (PIS) across 2 years, and 6 chromosome regions were detected as being associated with type I resistance through interval mapping, among which Qfhi.nau-4B and Qfhi.nau-5A with the resistance alleles originating from Wangshuibai and Qfhi.nau-2B with the resistance allele from Nanda 2419 were consistently detected. Qfhi.nau-4B and Qfhi.nau-5A had the largest effects among the detected QTLs and for the most part, both showed additive allelic effects. The former was also partially dominant. In addition, 4 pairs of significant interaction loci were identified. These results demonstrated that wheat scab resistance was under complex genetic control and also implied that early generation selection for type I resistance in scab resistance breeding was feasible with Wangshuibai as the parent.
Abstract: Pending the release of new genetic material with satisfactory resistance, grafting techniques may represent a quick, though expensive method for controlling race 1,2 of Fusarium oxysporum f. sp. melonis in Italian growing regions of melon (Cucumis melo L.). We evaluated the potential of grafting for resistance to this pathogen in 13 commercial melon rootstocks and various Cucurbitaceae spp. and determined productivity and fruit quality characteristics of grafting on resistant rootstocks. Following inoculation, P360 and PGM 96-05 commercial rootstocks, as well as Benincasa hispida, Cucumis metuliferus, Cucumis ficifolius, Cucurbita maxima, Cucurbita moschata, and Lagenaria siceraria were resistant to the race 1,2 of Fusarium. Yield and quality attributes of scion cultivars (Supermarket and Proteo) grafted on P360 and PGM 96-05 rootstocks were not improved relative to ungrafted controls. Grafts onto B. hispida negatively influenced both yield and fruit quality, while C. metuliferus, and C. zeyheri had negative impacts on productivity and fruit quality, respectively. These results indicate that rootstock influences on disease resistance as well as productivity and quality of scion fruit are important in determining the potential utility of grafting applications.
Author(s): Hemelrijck. W. V Wouters. P. F. W Brouwer. M Windelinckx. A Goderis. I. J. W. M Bolle. M. F. C. D Thomma. B. P. H. J Cammue. B. P. A Delaure. S. L
Abstract: The Arabidopsis thaliana mutant esa1 was previously shown to exhibit enhanced susceptibility to the necrotrophic fungal pathogens Alternaria brassicicola, Botrytis cinerea and Plectosphaerella cucumerina. In this work, we tried to elaborate on this susceptibility by investigating whether the esa1 phenotype can be extended to Fusarium species, a genus that includes several economically relevant pathogens. We show that the esa1 mutant exhibits increased susceptibility to several Fusarium species, including Fusarium oxysporum f. sp. matthiolae, F. solani, and F. culmorum. Furthermore, we show that the causal agent of the Panama disease on banana, F. oxysporum f. sp. cubense, a pathogen for which wild-type A. thaliana shows non-host resistance, causes enhanced lesion formation on esa1 as compared to wild-type plants, suggesting that esa1 is more sensitive to F. oxysporum f. sp. cubense. In addition, we were able to show that the A. thaliana wild-type resistance phenotype towards the latter pathogen can be partially restored by expression of the pathogenesis-related proteins PR1 or PR5 from tobacco in esa1, suggesting that PR1 and/or PR5 expression may be useful traits to obtain enhanced resistance to F. oxysporum f. sp. cubense in banana. As such, esa1 proves to be an ideal model system for research on the plant's defense response against fungal pathogens in general and Fusarium species in particular.
Abstract: A protocol for the generation of high yields of viable protoplasts has been developed for several highly branched (colonial) strains of the Quorn myco-protein fungus, Fusarium graminearum A3/5. Driselase was found to produce higher protoplast yields (ca 109 g-1 wet weight) than the other lytic enzymes tested (Glucanex, Novozyme, [beta]-glucuronidase, Sigma lytic enzyme, or ICN lytic enzyme), although yields differed for the various strains. Protoplast regeneration frequencies of 25–50% were observed when glucose (1·0 M) or sucrose (1·0 M) was used as the osmotic stabilizer. A highly branched strain of F. graminearum CC1-5, which grows better in submerged culture than the more sparsely branched wild-type strain (A3/5) was transformed using the hygromycin B resistance plasmid pAN7-1.
Abstract