Aggressiveness analysis of foliar fungi to leaves of wheat and rice crops

Abstract

The investigations were based on two surveys of wheat and one survey of rice. Alternaria alternata, Curvularia lunata, Helminthosporium tetramera and Bipolaris sorokiniana were isolated and identified from foliage and soil of both wheat and rice crops and their aggressiveness was studied by aggressiveness analysis screened out into different aggressiveness classes. The aggressiveness of isolated fungi was studied on wheat varieties (Inqalab-91 and Chakwal-86) and rice varieties (Basmati-385 and IRRI-6) under controlled conditions. In the foliar aggressiveness test of A. alternata, the overall number of aggressive isolates was higher on wheat varieties than rice. Bipolaris sorokiniana isolates showed foliar blight symptoms on wheat but not on rice varieties. In C. lunata, the overall number of aggressive isolates was higher on wheat. In the foliar aggressiveness test of H. tetramera, the number of non-aggressive isolates was almost the same on wheat and rice varieties. In the present study it became clear that A. alternate, B. sorokiniana, C. lunata and H. tetramera are common foliar pathogens in rice and wheat crops and can cause soil-borne and foliar diseases.     

Plant maintenance and environmental stress. Summarising the effects of contrasting elevation,soil, and latitude on Quercus ilex respiration rates

Aims

Rice (Oryza sativa L.), wheat (Triticum aestivum L.) and common bean (Phaseolus vulgaris L.) are major staple food crops consumed worldwide. Zinc (Zn) deficiency represents a common micronutrient deficiency in human populations, especially in regions of the world where staple food crops are the main source of daily calorie intake. Foliar application of Zn fertilizer has been shown to be effective for enriching food crop grains with Zn to desirable amounts for human nutrition. For promoting adoption of this practice by growers, it is important to know whether foliar Zn fertilizers can be applied along with pesticides to wheat, rice and also common bean grown across different soil and environmental conditions.

Methods

The feasibility of foliar application of zinc sulphate (ZnSO₄.7H₂O) to wheat, rice and common bean in combination with commonly used five fungicides and nine insecticides was investigated under field conditions at the 31 sites-years of seven countries, i.e., China, India, Pakistan, Thailand, Turkey, Brazil and Zambia.

Results

Significant increases in grain yields were observed with foliar Zn/foliar Zn?+?pesticide (5.2–7.7 % of wheat and 1.6–4.2 % of rice) over yields with no Zn treatment. In wheat, as average of all experiments, higher grain Zn concentrations were recorded with foliar Zn alone (41.2 mg kg^?1) and foliar Zn?+?pesticide (38.4 mg kg^?1) as compared to no Zn treatment (28.0 mg kg^?1). Though the magnitude of grain Zn enrichment was lesser in rice than wheat, grain Zn concentrations in brown rice were significantly higher with foliar Zn (24.1 mg kg^?1) and foliar Zn?+?pesticide (23.6 mg kg^?1) than with no Zn (19.1 mg kg^?1). In case of common bean, grain Zn concentration increased from 68 to 78 mg kg^?1 with foliar Zn alone and to 77 mg kg^?1 with foliar Zn applied in combination with pesticides. Thus, grain Zn enrichment with foliar Zn, without or with pesticides, was almost similar in all the tested crops.

Conclusions

The results obtained at the 31 experimental site-years of seven countries revealed that foliar Zn fertilization can be realized in combination with commonly-applied pesticides to contribute Zn biofortification of grains in wheat, rice and common bean. This agronomic approach represents a useful practice for the farmers to alleviate Zn deficiency problem in human populations.

     

Methyl jasmonate stimulates polyamines biosynthesisand resistance against leaf rust in wheat plants

Abstract

Leaf rust of wheat (Triticum aestivum L.), incited by Puccinia recondita ex Desm. f. sp. tritici Eriks, is one of the most important wheat diseases in Egypt. Methyl jasmonate (MJ) is a potential plant elicitor which induces a wide range of chemical and anatomical defense reactions in conifers and might be used to increase systemic resistance against biotic damage. In the greenhouse, different concentrations of MJ (10, 20 and 30 mM) were applied as seed soaking plus foliar spray or only as foliar spray to control leaf rust and induction of secondary compound production in leaves of wheat plants. Foliar spray was applied after 30 and 50 days of sowing. Results indicated that all concentrations and treatments reduced the severity of rust disease caused by P. recondita f. sp. tritici in wheat leaves during 45 days of inoculations. Disease incidence was decreased significantly in MJ-treated plants as seed soaking plus foliar spray with 20 and 30 mM when compared to 10 mM MJ or control plants. The study revealed that, with increasing concentrations of MJ, the secondary metabolites were greatly increased. Endogenous levels of both free and conjugated putrescine, spermidine and spermine increased in response to the elicitor. Activities of polyamine biosynthetic enzymes of ornithine decarboxylase (ODC) and polyamine oxidase (PAO) displayed up to threefold increases relative to untreated control. Moreover, significant increases in activities of plant defense-related protein, enzymes as peroxidase and chitinase as well as free and conjugated phenols contents were recorded in treated plants compared with untreated and infected plants. Furthermore, MJ treatment increased the chlorophyll-a, chlorophyll-b and carotenoids pigments contents, the higher increase was obtained with combined treatment between seeds soaking plus foliar spray at 20 and 30 mM of MJ. Under field conditions, three concentrations of MJ, i.e. 10, 20 and 30 mM as combined treatment between seeds soaking plus foliar spray or only as foliar spray were applied to study their effect against rust disease. Foliar spray was applied after 30 and 80 days of sowing. Results showed that the high reduction in disease severity was obtained with combined treatments between seeds soaking plus foliar spray with MJ at 20 and 30 mM compared with other treatments and control. At the same time, all treatments increased the growth and grain yield of wheat plants. It could be suggested that combination treatment between seeds soaking plus foliar spray with methyl jasmonate might be used commercially for controlling rust disease of wheat plants under field conditions.     

Virulence of Helminthosporium tetramera for root rot and foliar blight on wheat and rice crops and characterization by RAPD-PCR

Abstract

Helminthosporium tetramera isolates were isolated and identified from root of wheat and rice crops and their aggressiveness was studied using aggressiveness analysis in the greenhouse. Isolates of H. tetramera were genetically characterized using Random Amplified Polymorphism DNA (RAPD). The investigations were based on two surveys of wheat and one survey of rice. In root aggressiveness analysis, the overall number of aggressive isolates was higher on wheat compared to rice. In the foliar aggressiveness test, the number of non-aggressive isolates was almost the same on wheat and rice varieties. RAPD was used to study the polymorphism and genetic variation within the population of H. tetramera that established to study correlation between taxonomical, aggressiveness and genetical characters. The H. tetramera tree is constructed based on the pattern of bands. This study highlighted the correlation between morphological, aggressiveness and genetic variations of H. tetramera.     

Biofertilizers and/or some micronutrients role on wheat plants grown on newly reclaimed soil

Pot experiment was conducted to study the effect of biofertilizers (inoculation with different bacterial isolates), foliar spraying with some micronutrients (Mn, Zn, Fe and Mn+Zn+Fe) and their interaction on growth, physiological parameters and nutrients content of wheat plants grown on reclaimed soil. Pot experiment was conducted in the greenhouse of National Research center, The experimental design was split plot with four replicates. Four biofertilizer treatments (un‐inoculated, Bacillus polymyxa, Azotobacter chroococcum or Azosprillium barasilense) were used and randomly distributed in the main pots. The foliar treatments with micronutrients were randomly distributed in the sub plots. The growth parameters (plant height, leaf area, roots, shoots and whole plant dry weights and number of tillers & leaves per plant); some physiological parameters (soluble sugar %, protein %, polysaccharide %, chl. A+b μg cm^?1 leaf per plant, carotenoids μg g^?1, IAA mg kg^?1 and psll mol DCPIP reduced per mg chl. per h) and nutrient contents (N, P, K, Mg, Mn, Zn and Cu) of wheat plants were significantly increased by inoculating wheat grains with different bacteria as compared with un‐inoculated plants (control). The highest values of all the mentioned parameters were obtained by using Azospirillum brasilense followed by Azotobacter chroococcum and Bacillus polymyxa in decreasing order. Foliar spraying treatments significantly increased the growth parameters, physiological parameters as well as nutrients content of wheat plants as compared with control. Highest values were obtained by using (Mn+Fe+Zn) treatment followed by Zn, Fe and Mn in decreasing order. Micronutrients in wheat plants differed as the foliar treatments were differed, so application of any micronutrient individually significantly increased its content and enhanced the content of other micronutrients in wheat. Interaction between the used biofertilizers and foliar spraying with micronutrients significantly affected all the studied parameters of wheat plants, the highest were obtained by inoculating wheat grains with Azospirillum brasilense and spraying the plants with (Mn+Fe+Zn) treatment, while the lowest values were attained by un‐inoculated grains (control) and spraying the wheat plants with tap water (control). Effective microorganisms in combination with micronutrients could be recommended to farmers to lead higher wheat yield.     

Influence of Pak choi plant cultivation on Se distribution,speciation and bioavailability in soil

Background and aims

The combination of plant breeding and agronomic biofortification is the most reasonable approach to minimize zinc (Zn) deficiency-related problems in humans, but also in crop production. However, its efficiency and suitability under Mediterranean conditions and its effects on the grain yield and quality parameters are not well known.

Methods

Field experiments were conducted over two years in south-eastern Portugal, where soils are deficient in Zn. Ten advanced breeding lines and three commercial varieties of bread-making wheat were fertilized with four Zn treatments as following: i) control, ii) soil Zn application, iii) foliar Zn application and iv) both soil and foliar Zn application.

Results

Low rainfall produced 46 % more of grain Zn concentration but about 67 % less of grain yield. Grain Zn concentration varied greatly across treatments and cultivars with INIAV-1, INIAV-6, INIAV-9 and the commercial varieties being the most efficient. There were no significant increases in Zn concentrations due to soil Zn application, but gains higher than 20 mg kg^?1 were obtained both with foliar and soil+foliar Zn applications. Grain yield was not significantly higher in foliar application, but increased to about 10 % in soil, and about 7 % in soil+foliar applications, respectively.

Conclusions

In soils with low Zn availability, the best strategy to improve grain Zn concentrations has been to select the most efficient cultivars for Zn accumulation with the added application of Zn in soil+foliar form.

     

Photosynthetic characteristics of non‐foliar organs in main C3 cereals

Photosynthesis in non‐foliar organs plays an important role in crop growth and productivity, and it has received considerable research attention in recent years. However, compared with the capability of photosynthetic CO₂ fixation in leaves, the distinct attributes of photosynthesis in the non‐foliar organs of wheat (a C₃ species) are unclear. This review presents a comprehensive examination of the photosynthetic characteristics of non‐foliar organs in wheat. Compared with leaves, non‐foliar organs had a higher capacity to refix respired CO₂, higher tolerance to environmental stresses and slower terminal senescence after anthesis. Additionally, whether C₄ photosynthetic metabolism exists in the non‐foliar organs of wheat is discussed, as is the advantage of photosynthesis in non‐foliar organs during times of abiotic stress. Introducing the photosynthesis‐related genes of C₄ plants into wheat, which are specifically expressed in non‐foliar organs, can be a promising approach for improving wheat productivity.     

Foliar δ15 N patterns are dependent on seasonal and spatial variations as shown in lowland Scottish scrub

Summary

Patterns of foliar δ¹⁵ N can suggest testable hypotheses concerning N use among and within plant species. However, both spatial and time-series sampling is required to establish how the patterns vary within and among species. On a seasonal basis, foliar δ^l5 Nrankings may change among the species compared. When symbiotic N₂-fixers are among the plants sampled, N₂-fixation may be temporally disjunct from the near-0%c, expected foliar δ¹⁵ N, which is usually attributed to N₂-fixation, and the fates of previously fixed N may not be apparent from a net foliar δ¹⁵ N of either soil or plants.     

小麦/玉米轮作田根际微生物多样性分析

【背景】小麦/玉米轮作是中国粮食作物主要种植模式之一,目前对小麦/玉米轮作田根际土壤微生物差异变化缺乏全面的了解。【目的】明确小麦/玉米根际土壤微生物差异变化并了解其潜在功能。【方法】以小麦/玉米根际土壤为材料,运用细菌16S rRNA基因和真菌rDNA ITS基因测序,分析小麦/玉米根际土壤微生物多样性。【结果】玉米季微生物丰富度高于小麦季,而多样性无明显差异。放线菌门(Actinobacteria)、变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)和绿弯菌门(Chloroflexi)为小麦季和玉米季根际土壤的优势细菌门,优势真菌门为子囊菌门(Ascomycota)。小麦季和玉米季共有细菌和真菌分别是631个和261个,小麦季特有细菌和真菌分别是38个和58个,玉米季特有细菌和真菌分别是25个和39个。LEfSe分析(LDA阈值为2)细菌和真菌表明,放线菌纲(Actinobacteria)和微囊菌目(Microascales)在小麦季富集,鞘脂单胞菌目(Sphingomonadales)和银耳纲(Tremellomycetes)在玉米季富集。小麦季、玉...     

The effect of applied sulphur on the growth, grain yield and control of powdery mildew in spring wheat

During the years 1998 and 1999, two field experiments were conducted at the University of Wales, Aberystwyth, UK, to test the effects of soil‐ and foliar‐applied sulphur (S) in spring wheat. S was applied at 0, 20, 40, 60 kg ha^?1 in 1998 and at 60 kg ha^?1 in 1999, using CaSO₄ as a source for the soil application and micronised S (Thiovit, 80%), with and without an organosilicone adjuvant, as a source for the foliar application. Senescence was retarded and grain yield was increased in 1998, following application of foliar S in conjunction with the organosilicone adjuvant. Application of foliar S was associated with a reduction in the level of mildew (Erysiphe graminis) recorded on the upper leaves and ears of the canopy. In 1999, grain yield was unaffected by treatments. A low level of mildew in the crop, particularly on the ears, is thought to be the reason for the lack of response in spite of the fact that senescence was retarded with foliar S application. A combined application of foliar S and commercial fungicide (cyproconazole) to the crop appeared to be more effective at controlling mildew than either S or fungicide applied alone. The study shows that there may be a role for S in a low‐input/organic wheat production system, where there is a need to reduce artificial inputs.     

Introduction of Thinopyrum intermedium ssp. trichophorum chromosomes to wheat by trigeneric hybridization involving Triticum,Secale and Thinopyrum genera

Main conclusion

Fluorescence in situ hybridization and molecular markers have confirmed that several chromosomes from Thinopyrum intermedium ssp. trichophorum have been added to a wheat background, which originated from a cross between a wheat– Thinopyrum partial amphiploid and triticale. The lines displayed blue grains and resistance to wheat stripe rust.

Thinopyrum intermedium has been used as a valuable resource for improving the disease resistance and yield potential of wheat. With the aim to transfer novel genetic variation from Th. intermedium species for sustainable wheat breeding, a new trigeneric hybrid was produced by crossing an octoploid wheat–Th. intermedium ssp. trichophorum partial amphiploid with hexaploid triticale. Fluorescence in situ hybridization (FISH) revealed that Thinopyrum chromosomes were transmitted preferably and the number of rye chromosomes tended to decrease gradually in the selfed derivatives of the trigeneric hybrids. Four stable wheat–Th. intermedium chromosome substitution, addition and translocation lines were selected, and a 2J^S addition line, two substitution lines of 4J^S(4B) and 4J(4B), and a small 4J.4B translocation line were identified by FISH and molecular markers. It was revealed that the gene(s) responsible for blue grains may located on the FL0.60–1.00 of long arm of Th. intermedium-derived 4J chromosome. Disease resistance screenings indicated that chromosomes 4J^S and 2J^S appear to enhance the resistance to stripe rust in the adult plant stage. The new germplasm with Th. intermedium introgression shows promise for utilization of Thinopyrum chromosome segments in future wheat improvement.

     

Increasing use efficiency of boron fertilisers by rescheduling the time and methods of application for crops in India

Boron-deficiency is prevalent in light-textured acidic soil regions receiving high precipitation. Crop use efficiency of fertiliser B is also low under such B-leaching environments. For high leaching regimes, we hypothesised that the optimal timing and method of B application would vary with the crop sensitivity to B-deficiency and periods of peak demand for B. The aim of the present experiment was to vary the timing and method of B application to increase use efficiency on typical B-deficient Entisols. Mustard (Brassica campestris L.), wheat (Triticum aestivum L.) and potato (Solanum tuberosum L.) were the test crops. There were seven treatment combinations of B, applied either to soil or as foliar sprays at different doses and growth stages of the crops. Biomass and yield related characters of the crops at harvest, B concentration in plants and its uptake increased with B application being highest in mustard, followed by potato and wheat. Foliar application, in general had higher economic benefits than soil application. Split application of B either to soil (as basal and 25 days after sowing) or foliar sprays (at 25 and 40 and 25 and 45 days after sowing for mustard and potato, respectively) had an edge over a single application. For wheat, a single late application of B (at 45 or 60 days after sowing through soil or foliar spray, respectively) was more effective than the early or split application in increasing yields. Better use efficiency of B can thus be achieved if it is applied late for wheat but in splits over a longer period for mustard and potato with higher economic benefits.     

Does exogenous application of 24-epibrassinolide ameliorate salt induced growth inhibition in wheat (Triticum aestivum L.)?

A greenhouse experiment was conducted to assess whether exogenously applied 24-epibrassionlide (24-epiBL) could alleviate the adverse effects of salt on wheat. Two hexaploid wheat (Triticum aestivum L.) cultivars, S-24 (salt tolerant) and MH-97 (moderately salt sensitive), were grown under control (0 mM NaCl in full strength Hoagland’s nutrient solution) or saline conditions (150 mM of NaCl in full strength Hoagland’s nutrient solution). After 41 days growth of wheat plants under saline conditions, 24-epiBL was applied as a foliar spray. Four levels of BR were used as 0 (water spray), 0.0125, 0.025, and 0.0375 mg l⁻¹. Application of 24-epiBL increased plant biomass and leaf area per plant of both cultivars under non-saline conditions. However, under saline conditions, improvement in growth due to exogenous 24-epiBL was observed only in S-24. Photosynthetic rate was reduced due to salt stress in both cultivars, but this inhibitory effect was ameliorated significantly by the exogenous application of 24-epiBL. Exogenously applied 24-epiBL also enhanced the photosystem-II efficiency in both cultivars measured as F _v /F _m ratio. Although the activities of antioxidant enzymes, Superoxide dismutase (SOD), Peroxidase (POD) and Catalase (CAT) were increased due to salt stress in both wheat cultivars, exogenously applied 24-epiBL had a varying effect on the antioxidant system. The activity of SOD remained unaffected in both cultivars due to 24-epiBL application, but that of POD and CAT was promoted in the salt stressed plants of cv. S-24 only. In conclusion, improvement in growth in both wheat cultivars due to foliar applied 24-epiBL was found to be associated with 24-epiBL-induced enhancement in photosynthetic capacity. The 24-epiBL-induced regulation of antioxidant enzymes or growth under saline conditions was cultivar specific.     

Three modes of asexual reproduction in the moss Octoblepharum albidum

Abstract

Populations of Octoblepharum albidum growing in very moist and shaded habitats were found to have three kinds of asexual reproduction. First, the production of foliar gemmae along the upper half of leaf margins. Second, the production of protonema gemmae on protonemata originated from foliar gemmae. Third, the production of buds and new shoots at leaf tips. The formation of new shoots is further repeated at the leaf tips of the new shoots, giving the plant the character of a 'walking moss'.     

Endophytic colonisation of tobacco,corn, wheat and soybeans by the fungal entomopathogen Beauveria bassiana (Ascomycota,Hypocreales)

We demonstrate the effectiveness of three inoculation methods (foliar spray, seed immersion and root immersion) in establishing fungal the entomopathogen Beauveria bassiana as an endophyte in tobacco, corn, wheat and soybean. Colonisation of leaves by B. bassiana was assessed 7, 14, 21 and 28 days post-inoculation. There were significant differences (p < 0.001) in endophytic colonisation among the different inoculation techniques.     

Genes WHEAT FRIZZY PANICLE and SHAM RAMIFICATION 2 independently regulate differentiation of floral meristems in wheat

Background

Inflorescences of wheat species, spikes, are characteristically unbranched and bear one sessile spikelet at a spike rachis node. Development of supernumerary spikelets (SSs) at rachis nodes or on the extended rachillas is abnormal. Various wheat morphotypes with altered spike morphology, associated with the development of SSs, present an important genetic resource for studies on genetic regulation of wheat inflorescence development.

Results

Here we characterized diploid and tetraploid wheat lines of various non-standard spike morphotypes, which allowed for identification of a new mutant allele of the WHEAT FRIZZY PANICLE (WFZP) gene that determines spike branching in diploid wheat Ttiticum monococcum L. Moreover, we found that the development of SSs and spike branching in wheat T. durum Desf. was a result of a wfzp-A/TtBH-A1 mutation that originated from spontaneous hybridization with T. turgidum convar. сompositum (L.f.) Filat. Detailed characterization of the false-true ramification phenotype controlled by the recessive sham ramification 2 (shr2) gene in tetraploid wheat T. turgidum L. allowed us to suggest putative functions of the SHR2 gene that may be involved in the regulation of spikelet meristem fate and in specification of floret meristems. The results of a gene interaction test suggested that genes WFZP and SHR2 function independently in different processes during spikelet development, whereas another spike ramification gene(s) interact(s) with SHR2 and share(s) common functions.

Conclusions

SS mutants represent an important genetic tool for research on the development of the wheat spikelet and for identification of genes that control meristem activities. Further studies on different non-standard SS morphotypes and wheat lines with altered spike morphology will allow researchers to identify new genes that control meristem identity and determinacy, to elucidate the interaction between the genes, and to understand how these genes, acting in concert, regulate the development of the wheat spike.

     

Effect of <Emphasis Type="Italic">Trichoderma</Emphasis> spp. isolates for biological control of tan spot of wheat caused by <Emphasis Type="Italic">Pyrenophora tritici-repentis</Emphasis> under field conditions in Argentina

Trichoderma spp. have been used as biocontrol agents to protect plants against foliar diseases in several crops, but information from field assays is scarce. In the present work, experiments were carried out to determine the effect of six isolates of Trichoderma harzianum and one isolate of T. koningii on the incidence and severity of tan spot, caused by Pyrenophora tritici-repentis (anamorph: Drechslera tritici-repentis) under field conditions. Significant differences between years, wheat cultivars and treatments were found. In 2003, two of the isolates assayed (T5, T7) showed the best performance against the disease applied as seed treatments or sprayed onto wheat leaves at different stages. The application of six of the treatments on wheat plants significantly reduced disease severity by 16 to 35% in comparison with the control. Disease control provided by isolate T7 was similar to that provided by the fungicide treatment (56% reduction). This is the first report on the efficacy of Trichoderma spp. against tan spot under field conditions in Argentina.     

Structure and dynamics of retrotransposons at wheat centromeres and pericentromeres

Little is known of the dynamics of centromeric DNA in polyploid plants. We report the sequences of two centromere-associated bacterial artificial chromosome clones from a Triticum boeoticum library. Both autonomous and non-autonomous wheat centromeric retrotransposons (CRWs) were identified, both being closely associated with the centromeres of wheat. Fiber-fluorescence in situ hybridization and chromatin immunoprecipitation analysis showed that wheat centromeric retrotransposons (CRWs) represent a dominant component of the wheat centromere and are associated with centromere function. CRW copy number showed variation among different genomes: the D genome chromosomes contained fewer copies than either the A or B genome chromosomes. The frequency of lengthy continuous CRW arrays was higher than that in either rice or maize. The dynamics of CRWs and other retrotransposons at centromeric and pericentromeric regions during diploid speciation and polyploidization of wheat and its related species are discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Zhao Liu and Wei Yue made an equal contribution to this work.     

Changes of microflora of wheat roots after foliar application of urea

Upper parts of wheat grown in containers with brown soil were four-times repeatedly treated with a solution of urea. The foliar application of urea resulted in a considerable increase of the number of bacteria in the roots and a decrease of the number of fungi. Seventeen and 13 genera of fungi could be detected in the rhizosphere of the treated plants, 3 and 5 weeks, respectively, after the application, whereas 23 and 16 genera could be identified in the rhizoplane of the treated plants. Fungi of the generaFusarium andPenicillium predominated in the root region. The foliar application of urea resulted in an increased relative occurrence of the genusFusarium and decreased relative representation of the genusPenicillium. Changes in the relative occurrence of other 18 genera of fungi present in small quantities on wheat roots could also be observed. The foliar application of urea affected not only numbers of fungi determined by the dilution plate method but also the occurrence of active hyphae.