SAPROPHYTIC BEHAVIOUR OF SOME CEREAL ROOT-ROT FUNGI: IV. SAPROPHYTIC SURVIVAL IN SOILS OF HIGH AND LOW FERTILITY

In southern New South Wales the resumption of ley land for wheat growing has been accompanied by an increase in take-all ( Ophiobolus graminis ) and Fusarium root rot ( Fusarium culmorum ). No such increase has been observed in foot and root rots of wheat caused by Helminthosporium sativum and Curvularia ramosa.
It is shown experimentally that these differences are related to the relative capacity of the causal fungi to persist in wheat straw buried in each of two unsterilized soils which, because of past cultural treatments, differed in their organic carbon and total nitrogen content. While the saprophytic survival of O. graminis and F. culmorum was promoted by high soil fertility that of H. sativum was markedly depressed. The survival of C. ramosa was little affected by soil fertility.
F. culmorum, H. sativum and C. ramosa each remained viable under the soil conditions best suited to their survival in one-third to one-half of the test straws for 2 years but O. graminis was not recovered after the 52nd week of sampling.     

A COMPARATIVE STUDY OF OPHIOBOLUS GRAMINIS AND FUSARIUM CULMORUM IN SAPROPHYTIC COLONIZATION OF WHEAT STRAW

The competitive saprophytic ability of Ophiobolus graminis has been compared with that of Fusarium cultnorum. Test pieces of wheat straw were buried in maize-meal-sand inoculum mixed in various proportions with unsterilized soil, according to the technique already described by Butler (1953). Some possible sources of variation in the results obtained by this technique have been investigated. Saprophytic colonization of the straw tissues by Ophiobolus graminis appeared to decline as invasion progressed from the outer to the inner tissues, presumably owing to continued competition with other saprophytes. An experiment using as inoculum the stubble of plants naturally infected by O. graminis suggests that saprophytic colonization of wheat straw by the take-all fungus can occur only to a negligible extent in the field.     

Soil conditions and the take-all disease of wheat: VIII. Further experiments on the survival of Ophiobolus graminis in infected wheat stubble

Assimilable nitrogen in various forms prolonged the life of Ophiobolus graminis in infected wheat straw, whether added directly to the straw or to the surrounding soil. When the infected straws were buried in washed quartz sand, 0.5 g. nitrogen per 100 g. air-dry straw was the optimum dressing for longevity of Ophiobolus. Addition of sodium phosphate did not significantly increase longevity.
Nitrogen is considered to prolong the life of Ophiobolus by enabling the mycelium to form new branch hyphae, which can explore unexhausted parts of the substrate; it is suggested that aged mycelium dies from carbohydrate starvation, through exhaustion of the zones of enzymic erosion around the hyphae. This hypothesis is supported by the extended life of the fungus in infected straws that were shaken twice weekly in 3 % dextrose solution.
Ophiobolus was found to survive longer in infected straws buried in a fallow soil than in the same soil under oats, mustard or trefoil; this finding suggests the use of catch crops as competitors with Ophiobolus for soil nitrogen.     

The effects of soil sterilants on the cereal cyst-nematode (Heterodera avenae Woll.), take-all (Ophiobolus graminis Sacc.) and yields of spring wheat and barley

In a 3-year field experiment on sandy loam at Woburn, methyl bromide, chloropicrin, D-D mixture, dazomet, formalin and mercury salts were applied in the first year only, or in the first and second years, before drilling spring wheat. In the third year, their residual effects on spring barley were measured. All sterilants except mercury decreased cereal cyst-nematode ( Heterodera avenae ) numbers and take-all ( Ophiobolus graminis ) incidence, and increased crop yields in the year they were applied. Dazomet gave the best control of H. avenae in the first year and controlled O. graminis best in both years of application. In the third year, O. graminis increased in all plots previously treated (except after two successive D-D treatments), but H. avenae increased only after formalin. Two formalin applications more than trebled the H. avenae egg count by the end of the third year and depressed the yield of barley. Two successive applications of chloropicrin gave the best nematode control.
Other fungus diseases, Fusarium foot rot, Pythium root rot, eye-spot ( Cercosporella herpotrichoides Fron.) and sharp eye spot ( Rhizoctonia solani Kühn), were uncommon and sterilants had no detectable effects on them. The largest aggregate straw yield (3-year total) was obtained from two applications of dazomet, but the best yields after treatment in the first year only were given by D-D and methyl bromide.     

Influence of a Fusarium culmorum inoculation of wheat on the progression of mycotoxin accumulation, ingredient concentrations and ruminal in sacco dry matter degradation of wheat residues

The Fusarium head blight (FHB)-susceptible winter wheat cv. Ritmo was inoculated with spores of Fusarium culmorum at the beginning of full blossom. Samples of whole wheat plants were taken once weekly from anthesis until harvest and subsequently fractionated into straw, glumes and spindles, which were examined for deoxynivalenol (DON) and zearalenone (ZON). Additionally, the content of crude protein (CP) and non-starch polysaccharides (NSP) was scrutinized. Synthesis of the Fusarium toxins DON and ZON generally differed in terms of date of formation and concentration. Final mean DON concentrations of 37.5, 28.1 and 5.0 mg/kg DM were measured in glumes, spindles and straw, respectively, at the time of harvest. At this time, maximal mean ZON concentrations of 587, 396 and 275 microg/kg DM in spindles, glumes and straw, respectively, were determined. Moreover, Fusarium infected wheat residues contained higher CP but lower NSP contents at the last three sampling dates. In addition, collective samples of wheat straw and chaff were taken to investigate the effect of the Fusarium contamination on their in sacco DM degradation in dairy cows. Samples were analysed for mycotoxins and selected quality parameters. The dried and milled collective samples of straw and chaff were weighed into nylon bags and subjected to ruminal incubation for 4, 8, 16, 24, 48, 72, 96 and 120 h in two dairy cows equipped with a permanent rumen cannula. Marked differences in level of mycotoxin contamination as well as in ingredient composition between the variants of straw and chaff were detected. Moreover, after 120 h rumen incubation the in sacco DM degradation of inoculated straw and chaff were lower compared to the accordant controls. The soluble fraction was increased in inoculated samples, whereas a diminishment in the potentially degradable but insoluble fraction was more pronounced. Thereby, a decrease in the potential degradability was obtained for inoculated straw and even if less pronounced for chaff compared to the non inoculated corresponding controls. In conclusion, infection with F. culmorum of wheat involves an increased risk of mycotoxin contamination in straw. Also, a Fusarium infection may have an impact on chemical composition and may result in Fusarium growth-related modifications of host cell wall components.     

西藏农作物病原真菌的区域分化初探*

在西藏农作物病原真菌调查基础上,综合分析西藏自然环境条件和社会经济条件对病原真菌分布的影响,将西藏病原真菌分布划分为5个区:(1) 喜马拉雅南侧暖热湿润区; (2)藏东温暖半湿润区; (3)藏南温暖半干旱区; (4) 西喜马拉雅温凉干旱区; (5) 藏北羌塘高寒区;     

Soil conditions and the take-all disease of wheat; control of the disease under continuous cultivation of a spring-sown cereal

In a field experiment on the control of take-all at the Woburn Experimental Station, winter wheat was followed by two consecutive crops of spring-sown barley. Samples of the barley crop were taken from the forty-eight plots of the experiment in 1945 and 1946, for estimation of root Disease Rating, and grain yields were also recorded. A comparison of six autumn treatments of the stubble has shown that treatments affecting the available nitrogen content of the soil exercised a predominant effect upon incidence of take-all in the following crop. Two effects of nitrogen applied in autumn have been distinguished: (1) an immediate effect, in assisting survival of Ophiobolus graminis in infected root and stubble residues; (2) a deferred effect, in promoting disease escape of the following crop. The ploughing in of straw in autumn was found to increase the incidence of take-all, presumably because the adverse deferred effect of decomposing straw in locking up available nitrogen and withholding it from the following crop. outweighed its beneficial immediate effect in helping to starve out O. graminis , by depriving the fungus of nitrogen. The autumn growth of undersown trefoil ( Medicago lupulina ) on the stubble land seenled to be entirely beneficial; active growth of the legume appeared to assist in starving out O. graminis , and nitrogen was released by decomposition of the trefoil in the soil after spring ploughing in time to benefit the barley crop immediately following.     

Antifungal activity of Artemisia annua endophyte cultures against phytopathogenic fungi.

Artemisia annua, well recognized for its production of antimalarial drug artemisinin, is seldom attacked by any of phytopathogenic fungi, which could be partially associated with the presence of endophytes. Present investigation is aiming at disclosing whether the endophytes inside A. annua produce antifungal substances. A total of 39 endophytes were isolated and fermented, and the ferment broth was evaluated in vitro for the antifungal activity against crop-threatening fungi Gaeumannomyces graminis var. tritici, Rhizoctonia cerealis, Helminthosporium sativum, Fusarium graminearum, Gerlachia nivalis and Phytophthora capsici. These plant pathogens are still causing wheat take-all, sharp eyespot, common rot, scab, snow mould, and pepper phytophthora blight, respectively. Out of 39 endophytes investigated, 21 can produce in vitro substances that are inhibitory to all or a few of the tested phytopathogens whereas the rest yielded nothing active. Moreover, the most active broth of endophyte IV403 was extracted with EtOAc and n-butanol, and comparisons of the antifungal activity of the extracts indicated that the major active metabolites were EtOAc-extractable.     

Extracellular xylanase production by Fusarium species in solid state fermentation

Fusarium sp. has been shown to be a promising organism for enhanced production of xylanases. In the present study, xylanase production by 21 Fusarium sp. isolates (8 Fusarium culmorum, 4 Fusarium solani, 6 Fusarium verticillioides and 3 Fusarium equiseti) was evaluated under solid state fermentation (SSF). The fungal isolate Fusarium solani SYRN7 was the best xylanase producer among the tested isolates. The effects of some agriculture wastes (like wheat straw, wheat bran, beet pulp and cotton seed cake) and incubation period on xylanase production by F. solani were optimized. High xylanase production (1465.8 U/g) was observed in wheat bran after 96 h of incubation. Optimum pH and temperature for xylanase activity were found to be 5 and 50 degrees C, respectively.     

In vitro antifungal activity of the tea tree (Melaleuca alternifolia) essential oil and its major components against plant pathogens

AIMS: The aim of this study was to examine the effect of Melaleuca alternifolia essential oil (TTO) and its principal components on four cereal-pathogenic fungi. METHODS AND RESULTS: The antimycotic properties of TTO and of terpinen-4-ol, gamma-terpinen and 1,8-cineole (eucalyptol) were evaluated in vitro on Fusarium graminearum, Fusarium culmorum and Pyrenophora graminea. Moreover, barley leaves infected with Blumeria graminis were treated with whole TTO. All the tested fungi were susceptible to TTO and its components. CONCLUSIONS: TTO exerted a wide spectrum of antimycotic activity. Single TTO purified components were more active than the whole oil in reducing in vitro growth of fungal mycelium and, among the tested compounds, terpinen-4-ol was the most effective. SIGNIFICANCE AND IMPACT OF THE STUDY: TTO and its components can be considered potential alternative natural fungicides.     

Efficacy of plant extracts against stored-products fungi

The fungistatic activity of six aqueous extracts of plants were tested against Aspergillus candidus, Aspergillus niger, Penicillium sp. and Fusarium culmorum. The plants were, chamomile (Anthemis nobilis L.), cinnamon (Cinnamomum verum J. Presl.), French lavender (Lavandula stoechas L.), garlic (Allium sativum L.), malva (Malva sylvestris L.) and peppermint (Mentha piperita L.). The more concentrated extracts of chamomile and malva inhibited totally the growth of the tested fungi with malva the most effective one.     

Mating type sequences in asexually reproducing Fusarium species

To assess the potential for mating in several Fusarium species with no known sexual stage, we developed degenerate and semidegenerate oligonucleotide primers to identify conserved mating type (MAT) sequences in these fungi. The putative alpha and high-mobility-group (HMG) box sequences from Fusarium avenaceum, F. culmorum, F. poae, and F. semitectum were compared to similar sequences that were described previously for other members of the genus. The DNA sequences of the regions flanking the amplified MAT regions were obtained by inverse PCR. These data were used to develop diagnostic primers suitable for the clear amplification of conserved mating type sequences from any member of the genus Fusarium. By using these diagnostic primers, we identified mating types of 122 strains belonging to 22 species of Fusarium. The alpha box and the HMG box from the mating type genes are transcribed in F. avenaceum, F. culmorum, F. poae, and F. semitectum. The novelty of the PCR-based mating type identification system that we developed is that this method can be used on a wide range of Fusarium species, which have proven or expected teleomorphs in different ascomycetous genera, including Calonectria, Gibberella, and Nectria.     

Fusarium culmorum is a single phylogenetic species based on multilocus sequence analysis

Fusarium culmorum is a major pathogen of wheat and barley causing head blight and crown rot in cooler temperate climates of Australia, Europe, West Asia and North Africa. To better understand its evolutionary history we partially sequenced single copy nuclear genes encoding translation elongation factor 1-α (TEF), reductase (RED) and phosphate permease (PHO) in 100 F. culmorum isolates with 11 isolates of Fusarium crookwellense, Fusarium graminearum and Fusarium pseudograminearum. Phylogenetic analysis of multilocus sequence (MLS) data using Bayesian inference and maximum parsimony analysis showed that F. culmorum from wheat is a single phylogenetic species with no significant linkage disequilibrium and little or no lineage development along geographic origin. Both MLS and TEF and RED gene sequence analysis separated the four Fusarium species used and delineated three to four groups within the F. culmorum clade. But the PHO gene could not completely resolve isolates into their respective species. Fixation index and gene flow suggest significant genetic exchange between the isolates from distant geographic regions. A lack of strong lineage structure despite the geographic separation of the three collections indicates a frequently recombining species and/or widespread distribution of genotypes due to international trade, tourism and long-range dispersal of macroconidia. Moreover, the two mating type genes were present in equal proportion among the F. culmorum collection used in this study, leaving open the possibility of sexual reproduction.     

Observations on take-all and eyespot diseases of wheat in Yorkshire

Wheat crops were surveyed in Yorkshire from 1944 to 1946 on farms where crops were reported to be unsatisfactory. Take-all ( Ophiobolus graminis (Sacc.) Sacc.) and eyespot ( Cercosporella herpotrichoides Fron.) were both found to be present; the latter is the most serious trouble on the better wheat lands.
The variation in the incidence of these diseases on selected farms during the three seasons has been compared.
The effect of rotation has been examined; both diseases were found to be encouraged by too frequent cropping with wheat or barley. The incidence of disease in wheat crops following a 1-year seeds ley was found to be influenced by the nurse crop used to undersow the seeds, and also by the time at which the ley was ploughed up. Oats were found to be preferable to either wheat or barley as a nurse crop, and in 1946 late ploughing considerably reduced the amount of eyespot disease present in the following wheat crop.
A 1-year ley is considered to be of too short a duration to ensure the disappearance from the soil of Ophiobolus graminis and Cercosporella herpotrichoides surviving from the previous crop, and a period of 2–3 years is suggested as being desirable.     

Methoxyhydroquinone, a Growth Inhibitor of Ophiobolus graminis, in Leaves of Oat Seedlings

A methanol extract of leaves of oat seedlings grown in sand cultures in the dark contained a compound which inhibited the growth of Ophiobolus graminis. The inhibitory factor was isolated and proved to be present in the plant as methoxyhydroquinone glucoside. The glucoside was readily hydrolysed to the corresponding aglucone. The methoxyhydroquinone, or possibly its oxydation product, methoxy-P-benzoquinone, was inhibitory to both Ophiobolus graminis var. graminis and Ophiobolus graminis var. avenae, whereas Fusarmm oxysporum var. lycopcrsici was not affected. Synthetic methoxyhydroquinone at 80 mg/l gave a 100% inhibition of Ophiobolus graminis var. graminis. After being exposed to 80 mg/l of the inhibitor for 24 h the mycelium was unable to initiate growth when transferred to a fresh nutrient solution. Only extracts from young leaves showed inhibitory activity, extracts from mature leaves giving no inhibition. The hydroquinone, or its glucoside, was not detected in roots of young seedlings, where avenacin was the only antifungal compound present.     

Occurrence of Ophiobolus graminis var. Avenae on wheat crops in the field

Ophiobolus graminis var. Avenae has been found on oat crops in ten counties in Scotland. It has also been shown to attack wheat crops in the same districts.     

Airborne fungal spores in the Campus of Anchieta (La Laguna,Tenerife/Canary Is.)

A quantitative and qualitative study was carried out of the atmospheric fungal propagules in two university buildings in the Campus of Anchieta (La Laguna, Tenerife, Canary Islands, Spain) and in the outdoor atmosphere, in order to ascertain the most abundant fungi and the concentration of spores in the air, as possible sources of respiratory allergies caused by this type of aeroallergens. Sampling was carried out using two kinds of traps (Burkard Personal Culture Sampler and Burkard Personal Slide Sampler), as well as adhesive tape. Sample 1, indoor, identified between 650-320 CFU m -3 depending on the culture medium, with outdoor values between 670-440 CFU m -3 ; sample 2, recorded between 630-80 CFU m -3 inside and 580-300 CFUm -3 in the outdoor atmosphere. The most represented genera were Cladosporium and Penicillium , although the following were also identified: Agaricales, Alternaria, Aspergillus, Botrytis, Drechslera, Coprinus, Curvularia, Chaetomium, Exserohilum, Fusarium, Helminthosporium, Leptosphaeria , Myxomycetes, Paecilomyces, Pleospora, Stemphylium, Tetraploa, Torula and Ulocladium .     

Two plant alkaloids isolated from<Emphasis Type="Italic">Corydalis longipes</Emphasis> as potential antifungal agents

The alkaloids N-methylhydrasteine hydroxylactam and 1-methoxyberberine chloride were isolated from Corydalis longipes. Both alkaloids showed high efficacy individually (in concentration of 50-150 ppm) and also in a 1:1 mixture against spore germination of some fungi, viz. Alternaria alternata, A. brassicae, Curvularia maculans, Curvularia sp., Colletotrichum gloeosporioides, Colletotrichum sp., Helminthosporium speciferum, H. pennisetti, Helminthosporium sp., and Ustilago cynodontis. The antifungal effect of single compounds was dose-dependent. If the mutual ratio of the two components in the mixture was changed from 1:1 to a major content of any of the two compounds, the inhibitory effect on spore germination decreased.     

Antimicrobial activity of extracts of chemical races of the lichen Pseudevernia furfuracea and their physodic acid, chloroatranorin, atranorin, and olivetoric acid constituents

The antimicrobial activity and the MIC values of the ethanol, chloroform, diethyl ether, and acetone extracts of the chemical races of Pseudevernia furfuracea (var. furfuracea and var. ceratea) and their physodic acid, chloroatranorin, atranorin, and olivetoric acid constituents have been investigated against some microorganisms. Nearly all extracts of both chemical races showed antimicrobial activity against Aeromonas hydrophila, Bacillus cereus, Bacillus subtilis, Listeria monocytogenes, Proteus vulgaris, Staphylococcus aureus, Streptococcus faecalis, Yersinia enterocolitica, Candida albicans, Candida glabrata, Alternaria alternata, Ascochyta rabiei, Aspergillus niger, Fusarium culmorum, Fusarium moniliforme, Fusarium oxysporum, Fusarium solani, and Penicillium notatum. There was no antimicrobial activity of the extracts against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Pseudomonas syringae, Salmonella typhimurium, Alternaria citri, Alternaria tenuissima, and Gaeumannomyces graminis. Chloroatranorin and olivetoric acid were active against the same microorganisms with few exceptions. Physodic acid was active against about the same bacteria and yeasts and inactive against all of the filamentous fungi tested. Also no activity of atranorin against the filamentous fungi was observed.     

Resistance of cultivars and breeding lines of spring wheat to Fusarium culmorum and powdery mildew

Twelve Polish spring wheat cultivars and 18 spring wheat accessions from CIMMYT, Mexico, were examined for resistance to a highly pathogenic Fusarium culmorum strain KF846 and powdery mildew in 5-year field experiments. Resistant wheat cultivars (Sumai 3 and Frontana) served as controls. The mean percentage of Fusarium-damaged kernels (% FDK) for 5 years was lower in CIMMYT accessions (16.7%) than in Polish spring cultivars (28.3%). In all Polish spring cultivars, % FDK was higher than in the control cultivars Sumai 3 and Frontana (12-20%). The mean disease score (on a scale of 1-9) for powdery mildew (natural infection) for all examined cultivars and lines ranged from 0 to 7 and in the Polish spring cultivars was significantly lower (0-5). Cultivars Eta, Henika, Ismena, Jasna and Olimpia were found to be the least susceptible to powdery mildew in field experiments. The laboratory host-pathogen tests with Blumeria graminis f. sp. tritici isolates showed that only two cultivars were characterized by identical resistance patterns as the standard differential lines with documented resistance genes. Cultivar Alkora had the gene Pm3d, and Henika had Pm5. The gene Pm3d was identified in cultivars Jasna and Eta in combination with another unknown gene/genes. Cultivars Santa and Torka had the gene Pm5 in combination with another unknown gene/genes. Four cultivars: Banti, Ismena, Olimpia and Sigma, showed resistance to all mildew isolates employed in a laboratory test. The accession IPG-SW-14 was the least susceptible to both pathogens (F. culmorum and powdery mildew) in all 5 years of experiments. This line is the best candidate for deriving new cultivars with improved resistance to fungal diseases.