Flag Smut Research Articles

Fusarium head blight of wheat in India‐variability in pathogens associated and sources of resistance: an overview

During 2019-20 crop season, India harvested record wheat production of 107.19 mt from an area of 30.5 mha thereby registering an all-time high productivity. The most serious fungal diseases which affect wheat production are rusts, spot blotch, Karnal bunt, head scab, powdery mildew, flag smut and loose smut. Recently outbreaks of Fusarium head blight (FHB) or head scab of wheat caused by Fusarium spp., has been reported from Canada, Europe, Asia, Australia and South America. In India, the disease can cause significant yield loss if rain occurs during mid anthesis in the foot hills of Punjab, Himachal Pradesh, Uttarakhand and hilly areas in Tamil Nadu. The Fusarium diseases are likely to increase under the impact of global warming and the fast adoption of reduced tillage practices in the main wheat belt, the north west plains of India. Fusarium graminearum is known to produce mycotoxins which affect human and animal health. Extensive disease surveys undertaken in Himachal Pradesh and Tamil Nadu (Wellington) during 2010–20 revealed the dominance of F. graminearum causing head blight of wheat in India. Pathogenic variation among Fusarium spp./isolates has been studied by inoculating on a set of wheat varieties under artificially inoculated conditions. These studies helped in identifying virulent F. graminearum isolates and their use in evaluating a large number of wheat genotypes for identifying sources of resistance. Genetic variation among F. graminearum isolates have been detected with molecular markers. Since most of the popular cultivars grown in India are susceptible to head scab, there is a need to evaluate a greater number of indigenous and exotic wheat lines for incorporating head scab resistance in popular wheat cultivars. This review provides an overview of the variation in pathogens associated with the disease and resistant sources available for breeding durable FHB resistant wheat varieties.

Bioefficay of fungicides against karnal bunt and flag smut of wheat in himachal pradesh

Bioefficay of fungicides against karnal bunt and flag smut of wheat in himachal pradesh

Molecular Diagnostic Assay for Rapid Detection of Flag Smut Fungus (Urocystis agropyri) in Wheat Plants and Field Soil.

Flag smut incited by Urocystis agropyri has the potential to cause substantial reduction in yield and quality of wheat production. An early and precise diagnosis is a key component in the successful management of flag smut of wheat. Therefore, a simple molecular assay for the rapid detection of U. agropyri was developed for the first time. To detect U. agropyri, species specific primers were developed by comparing the partial sequences of internal transcribed spacer (ITS) DNA region of U. agropyri with related and unrelated phytopathogenic fungi. The clear amplicons of 503 and 548 bp were obtained with the two sets of designed primers (UA-17F/UA-519R and UA-15F/UA-562R) from the genomic DNA of 50 geographic distinct isolates of U. agropyri. However, no amplicon was obtained from the DNA of other 21 related and unrelated phytopathogenic fungi which showed the specificity of the primers for the U. agropyri. PCR reaction was also set up to confirm the presence of U. agropyri spores in six different wheat varieties along with eleven distinct regional soil samples as template DNA. The presence of U. agropyri in all the soil samples collected from an infected field and plant tissue of diseased plants collected at two different stages (20 and 40 days post sowing) and the absence in the soils and plants of healthy plots indicated 100% reliability for detection of U. agropyri. This simple and rapid test can be employed for the detection of U. agropyri from enormous wheat and soil samples in very short time with less man power. Thus, the reported molecular assay is very specific for U. agropyri and requires less time and man power over conventional diagnosis which is often confused by coinciding morphological features of closely related fungal pathogens, and therefore, it can be used for quarantine surveillance of flag smut.

What causes flag smut of wheat?

The causal agent of flag smut of wheat is currently subject to strict quarantine regulations in many countries and is believed to have a wide host range on wild and cultivated grasses. This fungus has been classified as both Urocystis agropyri and Urocystis tritici. Urocystis agropyri was first described from Elymus repens in Germany and U. tritici was first described from Triticum vulgare (=T. aestivum). In 1953, G. W. Fischer placed U. tritici and a large number of other Urocystis species in synonymy with U. agropyri. The present study is the first attempt to clarify the taxonomy and phylogeny of flag smut pathogens of grasses using molecular analyses. Three loci, the internal transcribed spacer (ITS) region of rDNA, the RNA polymerase II subunit 2 (RPB2), and translation elongation factor (TEF) protein‐coding regions were used for phylogenetic reconstruction to determine the species boundaries of 24 Urocystis specimens from triticoid hosts. Results indicate that there are several distinct lineages of flag smut pathogens, including the causal agent of flag smut of wheat, which is supported as a separate species, U. tritici. Sequences from specimens on E. repens, which are retained as U. agropyri, grouped in a clade distinct from those on wheat and rye. The closest relatives of U. tritici were found to be U. hispanica from Aegilops and Urocystis sp. from Thinopyrum junceiforme and Elymus trachycaulis. Recognition that U. tritici is genetically distinct from U. agropyri sensu stricto will impact regulatory policy and facilitate the development of diagnostic tests.

Characterisation of endophytic Bacillus thuringiensis strains isolated from wheat plants as biocontrol agents against wheat flag smut

To explore effective and ecofriendly means of controlling wheat flag smut (WFS) using biocontrol agents, three endophytic strains (58-2-1, 37-1 and YC-1) of Bacillus sp. were isolated from winter wheat plants in China and identified as Bacillus thuringiensis based on their 16S rDNA sequences as well as phenotypic characteristics. Four morphological (leaf length, root length, dry weight and tiller numbers) and one physiological [root vigour (RV)] parameters of wheat plants treated by strains 58-2-1 and 37-1 were significantly enhanced compared to the control. The soluble sugar contents in the roots of wheat samples treated by the two strains were significantly lower than the control. The resistance of wheat varieties to WFS was investigated by inoculation tests. Of the 12 wheat varieties tested, 6 (Yunhan-618, Bainongaikang-58, Kaimai-20, Zhengmai-9023, 04-zhong-36 and Yanzhan-4110) were identified as WFS-highly resistant (HR), 3 (Pumai-9, Jinboshi-1 and Yunong-202) WFS-moderately resistant (MR), 1 (Yubao-1) WFS-susceptible (S) and 2 (Yumai-012 and Yunong-416) WFS-highly susceptible (HS) varieties. The Urocystis tritici-induced yield loss on the S/HS varieties was significantly higher than that on the HR/MR ones. The strains 58-2-1 and 37-1 had control efficacies of 6.7–100% (av.54.8%) and 33.3–100% (av. 66.5%) on 9 and 7 out of 12 varieties, respectively. The strains 58-2-1 and 37-1 had enhanced yields of 10.2–54.9% (av. 32.9%) and 2.8–43.4% (av. 24.8%) on 10 and 8 out of 12 varieties, respectively. This is the first report on endophytic B. thuringiensis strains isolated from wheat plants with the abilities to suppress WFS and to enhance yields on multiple wheat varieties.

Multiple Diseases, Insect Pests Resistant Genotypes and Their Utilization in Breeding for Resistance in Wheat and Triticale

A total of 347 numbers of genotypes of Triticum aestivum , 66 of T. durum , 8 of T. dicoccum and 18 of triticale possessing resistance against multiple diseases and insect pests resistance were taken for the study. These were identified resistant to biotic stresses through rigorous evaluation under artificially inoculated conditions at hot spot locations in six agro ecological zones of India during 1998-99 till 2011-12 cropping seasons. The diseases and insect pests targeted were three rusts (stem, leaf and stripe rust), Karnal bunt, flag smut, leaf blight, powdery mildew, loose smut, brown wheat mite, root aphid, foliar aphid and shoot fly. The seeds of these genotypes along with passport data on disease resistance were shared with breeders at 30 main wheat and triticale breeding centres in India. The percentage of centres utilized these genotypes for hybridization and resistance breeding ranged from 4.0-63.6%. The per cent utilization was maximum in case of T. aestivum followed by T. durum, T. dicoccum . The most preferred genotypes of T. aestivum were, ‘DBW 18’, ‘DBW 32’, ‘GW 276’, ‘HD 2851’, ‘HD 2964’, ‘HD 2997’, ‘HP 1872’, ‘HW 2044’, ‘HW 3027’, ‘HPW 42’, ‘HPW 155’, ‘HPW 237’, ‘HPW 285’, ‘HUW 620’, ‘HS 295’, ‘HS 318’, ‘HS 345’, ‘HS 375’, ‘HS 420’, ‘HS 468’, ‘HS 493’, ‘HW 2045’, ‘HW 3083’, ‘HW 5037’, ‘HW 5208’, ‘K 9351’, ‘K 9441’, ‘MACS 295’, ‘MACS 2959’, ‘NW 3087’, ‘NW 1012’, ‘PBW 373’, ‘PBW 475’, ‘PBW 521’, ‘PBW 550’, ‘PBW 554’, ‘PBW 573’, ‘PBW 589’, ‘Raj 3765’, ‘Raj 4012’, ‘RAJ 4120’, ‘RAJ 4131’, ‘UP 2425’, ‘UP 2719’, ‘VL 801’, ‘VL 868’ and ‘VL 907’. In case of T. durum, 66 genotypes were utilized by 4.0-36% centres and most liked were, ‘AKDW 4155’, ‘CDW 04’, ‘GW 1139’, ‘HD 4696’, ‘HI 8498’, ‘MACS 3313’, ‘PDW 267’ and ‘PDW 312’. Likewise, out of eight genotypes of T. dicoccum , ‘MACS 2956’ (32.0%) and ‘MACS 2971’ (15.0%) were used most. Utilization of 18 numbers of triticale genotypes was 4.0-14.8% only. It may be due to lesser preference of triticale as compared to bread and durum wheat for breeding. The major preference of breeders was on genotypes having resistance against three or two rusts depending on agro climatic zones. The genotypes having Lr34 gene which is known for providing resistance to leaf rust were also found to be resistant to other diseases and aphids. The incorporation of resistance genes from resistant genotypes shared in breeding programme has helped greatly in management of diseases and insect pests using host resistance and avoided or reduced application of costly fungicides on wheat and producing pesticide free wheat in India. The deployment of resistant cultivars strategically in areas of prevalence of diseases and insect pests helped to further curtail losses in yield and quality of wheat and outbreak of rusts and other diseases thus ensure food self sufficiency as well as export of surplus wheat in future. These genotypes will be good source for molecular studies related to multiple disease and insect pests.

Mapping of flag smut resistance in common wheat

Flag smut, caused by Urocystis agropyri, has been a problem in wheat production, but its incidence has declined with the use of resistant varieties and seed dressing. Diamondbird, an Australian wheat cultivar that carries high levels of resistance to flag smut, was crossed with susceptible Chinese landrace TH3929 and a doubled haploid (DH) population was developed. A linkage map comprising 386 markers was used for detection of genomic regions controlling flag smut resistance. Composite interval mapping identified five quantitative trait loci (QTL) with significant effects for flag smut resistance. QTL QFs.sun-3AL, QFs.sun-6AS, QFs.sun-1BL and QFs.sun-5BS were contributed by Diamondbird. Although TH3929 was susceptible, it contributed a minor QTL QFs.sun-3AS. QTL QFs.sun-3AL and QFs.sun-6AS were detected in both seasons and each explained more than 17 % of the variation in flag smut response. Other QTL QFs.sun-3AS, QFs.sun-1BL and QFs.sun-5BS explained 5–10 % of the phenotypic variation. DH lines that showed low flag smut levels carried combinations of three or more QTL. This is the first report on chromosomal location of flag smut resistance in a modern common wheat cultivar.

First Report of Leaf Smut on Fescue (Festuca rubra) Caused by Urocystis agropyri in Interior Alaska.

In June and early July of 2003 and July of 2007, a smut disease was found on fescue (Festuca rubra L.) at the Fairbanks Golf and Country Club and vicinities, Interior Alaska. Diseased plants were pale green-to-slightly yellow and stunted. The lesions were long, narrow, yellowish green streaks parallel to the veins of leaves and sheaths. At a later stage, sori developed under the epidermis and the leaves and sheaths turned silvery gray. Rupture of the epidermis resulted in the release of masses of black spores that covered the leaves, especially along and within infected sheaths. Microscopic observation showed spore balls consisting of one-to-four, dark reddish brown teliospores surrounded by small, hyaline-to-light brown sterile cells. The spore balls were globose to elongate and 16 to 32 × 18 to 38 μm. The teliospores were globose, dark reddish brown, and 7.5 to 20 μm in diameter. Urocystis agropyri is recognized by R. W. Smiley et al. (2) and J. D. Smith et al. (3) as occurring on turf grasses; K. Vánky (4) restricts this species to Elymus spp. and recognizes U. ulei as the valid species infecting Festuca spp, including F. rubra. On the basis of host symptoms and morphology of spores, the smut found on F. rubra in Alaska fits better with published descriptions of U. agropyri (Preuss) Schrot (2,3), however, it likely is not conspecific with flag smut of wheat. For molecular verification of this identification, DNA was isolated from teliospores with a DNeasy Plant Mini Kit (Qiagen, Valencia, CA). Primers were designed for amplification of the large subunit ribosomal gene based on the only two published sequences of U. ranunculi (Lib.) Moesz (GenBank Accession No. AF009879) and U. colchici (Schltdl.) Rabenh (GenBank Accession No. AF009878) (1). A 400-bp PCR product was amplified by the forward primer 3'-GCATTGTAAACTCAGAAGTGTTATCCG-5' and reverse primer 5'-TTCCCTAAACCTATATCCGGCG-3'. Nucleotide sequence of the PCR product (GenBank Accession No. AY547283) shared 97.7% homology with U. ranunculi and 98.2% with U. colchici. Comparison of nucleotide sequences will be more meaningful in the identification of species of Urocystis when additional sequences are published. To our knowledge, this is the first report of U. agropyri from turfgrass in Alaska.

First Report of Flag Smut of Wheat Caused by Urocystis agropyri in the United Kingdom.

An isolated occurrence of flag smut of wheat, caused by Urocystis agropyri (G. Preuss) J. Schröt., was confirmed in the county of Essex, UK, in autumn-sown winter wheat (Triticum aestivum L.) cv. Riband grown from certified seed. The origin of the infection is unknown. Symptoms were first observed on 22 May 1998. The presence of U. agropyri was confirmed on the basis of the macroscopic symptoms on the host and the morphology of the pathogen (2). Long gray-black streaks parallel with the veins were observed on leaf blades, especially the flag leaf, and on leaf sheaths. The streaks consisted of lines of fungal sori developing between the leaf veins, giving a striped appearance. Eruption of the sori through the epidermis of the leaves had caused them to fray, exposing dark brown to black powdery spore masses. Microscopic examination revealed spore balls measuring 20 to 28 μm in diameter containing 1 to 3 spores per ball. Spores were dark brown measuring 12 to 17.5 μm in diameter and were surrounded by light brown sterile cells measuring 7 to 7.5 μm. Affected plants were stunted to about half the height of healthy plants. Some affected plants tillered excessively and in some cases the ear failed to emerge from the boot. Some diseased leaves were twisted and, where the host epidermis had ruptured to expose the spore masses, the affected parts had the appearance of being covered in black soot. All of the symptoms are typical of flag smut on wheat. Flag smut has been observed on grasses in every continent except Antartica. However, the distribution of the pathogen on wheat is more limited. Flag smut of wheat is known to occur in at least some of the countries of the European Union as well as (e.g.) the USA and Australia. This finding is significant because it had been considered that U. agropyri on wheat had reached the limits of its ecoclimatic zone, since it requires specific environmental conditions for infection and disease development, particularly a mild winter and an arid summer (1). The climatic conditions in Essex between September 1997 when the affected crop was planted and May 1998 when symptoms were first observed were considerably drier and warmer than normal, thus favoring the pathogen. This is the first report of U. agropyri on wheat in the UK.

Control of Wheat Flag Smut by Soil Sterilization with Hot Water Injection

Control of Wheat Flag Smut by Soil Sterilization with Hot Water Injection

Triticum aestivum spp. vulgare (bread wheat) cv. Beulah

Beulah, with the parentage Cook x 2/Millewa/TM56 (TM56 = AUS10894/4 x Condor), is a semi-dwarf, early flowering, spring wheat with moderately strong straw and reaching ear emergence 2 days later than Meering. In silo group A (Mallee region), Beulah yields equal to Meering and higher than Cocamba, and is similar to these cultivars in silo group C (Wimmera region). Beulah is resistant to cereal cyst nematode [Heterodera avenae], moderately resistant to stripe rust [Puccinia striiformis] and flag smut [Urocystis agropyri], and has the stem rust [P. graminis f.sp. tritici] resistance genes Sr30 and Sr36, giving it resistance to the current Australian races of stem rust. Average milling yields of this hard-grained cultivar are 2% higher than those of Meering. The flour has mixing properties similar to those of Meering, while the dough is more extensible (2.2 cm longer). Overall baking quality of Beulah is good. Beulah is acceptable for the Australian Standard White class in Victoria.

Reactions of Wheat Cultivars to Flag Smut in Southern New South Wales.

Flag smut (Urocystis agropyr) was detected in a few crops of the wheat cultivar Rosella in southern New South Wales during 1986. Screening of cultivars, potential parents and breeding lines was undertaken from 1987 to assist in breeding cultivars resistant to flag smut. Most cultivars recommended in New South Wales have resistance but the cultivar Rosella is very susceptible and could enable flag smut to spread and cause severe losses if other control measures were not taken. Most breeding lines from the Central and Southern New South Wales wheat breeding program and introductions from CIMMYT were resistant, but a number of introductions from the USA and Europe were either susceptible or very susceptible to flag smut

Tiller and Rhizome Growth of Water-Stressed Poa pratensis 'Merion' Infected by Ustilago striiformis or Urocystis agropyri

Growth of tillers and rhizomes of Poa pratensis Merion' infected by Ustilago striiformis (cause of of stripe smut) or Urocystis agropyri (cause of flag smut) was evaluated in nutrient solution alone and amended with polyethylene glycol to provide increasing levels of osmotically induced water stress. U. striiformis had no effect on total dry weight of rhizomes per shoot but decreased the percentage of rhizome dry weight as a portion of total shoot dry weight. Dry weight of tillers per shoot increased and was a greater percentage of total shoot dry weight than the percentage of total shoot dry weight in healthy plants (...)

Chemical control in Western Australia of soilborne flag smut caused by Urocystis agropyri.

Seed dressings were tested at two field locations in 1986 for control of soilborne flag smut of wheat caused by Urocystis agropyri. Triazole fungicides effectively controlled soilborne flag smut at both locations. Carboxanilide fungicides were very effective at one location but less effective at the second location. No treatment significantly reduced emergence or grain yield.

Varietal Variation in Flag Smut Resistance of Wheat and Simple Technique for Screening

Varietal Variation in Flag Smut Resistance of Wheat and Simple Technique for Screening

The Incidence and Relative Importance of Wheat Diseases in Australia.

A survey of cereal plant pathologists in each State has shown that stem rust is ranked as potentially the most important foliar disease of wheat in most regions. Other major foliar diseases were stripe rust, flag smut, Septoria tritici blotch and leaf rust. Yellow spot has increased in importance since 1975 with the adoption of stubble retention farming in north-eastern Australia and Western Australia. Root rots of major importance were take-all, crown rot, Rhizoctonia bare patch and cereal cyst nematode. Bunt is potentially the most serious disease of the inflorescence but it is very rare because it is effectively controlled by seed-applied fungicides. Most biotrophic foliar diseases are well controlled by selection for resistance. Cultural practices and crop rotation are the main controls for root diseases, while fungicides are mainly used for control of inflorescence diseases. Regional differences in the severity and incidence are pronounced for several diseases.

Effect of Water Stress and Infection by Ustilago striiformis or Urocystis agropyri on Leaf Turgor and Water Potentials of Kentucky Bluegrass1

Plant tolerance to water stress can be measured, in part, by calculating the plants ability to maintain turgor during periods of water stress. Kentucky bluegrass (Poa pratensis) systemically infected by either Ustilago striiformis (Stripe smut) or Urocystis agropyri (Flag smut) exhibits greater mortality than noninfected plants during periods of water stress suggesting decreased drought tolerance with infection. The effects of water stress and systemic infection by the smut producing pathogens, Ustilago striiformis or Urocystis agropyri, were evaluated for their effects on leaf turgor and water potentials of Kentucky bluegrass ‘Merion’ grown in nutrient solution. Infection by either pathogen decreased leaf turgor and water potentials during light and dark periods as compared with noninfected controls. In addition, noninfected plants maintained higher leaf turgor and water potentials than infected plants as nutrient solution osmotic potentials were lowered with polyethylene glycol. Moisture release curves for single leaves from noninfected, U. striiformis‐, and U. agropyri‐infected plants were established to evaluate plants for osmotic adjustment by estimating leaf osmotic potentials and relative water contents at zero turgor as plants were grown in nutrient solution and nutrient solution amended with polyethylene glycol to increase water stress. Turgid weight/dry weight ratios also were calculated for noninfected and diseased leaves before and after water stress. Water stress lowered leaf osmotic potentials and relative water contents at zero turgor and decreased the turgid weight/dry weight ratios of noninfected and infected leaves. Noninfected plants exhibited lower osmotic potentials at zero turgor and maintained smaller turgid weight/dry weight ratios after water stress than infected plants, suggesting that infection by either pathogen inhibited osmotic adjustment and cell wall thickening in leaves of Kentucky bluegrass in response to water stress.

Leaf and Root Growth of Water‐Stressed Kentucky Bluegrass Infected by Ustilago striiformis or Urocystis agropyri1

The relative growth of the shoot vs. roots has proven to be a useful parameter in investigations of drought tolerance. In addition, overall plant growth has been used as a measure of tolerance to water stress. Kentucky bluegrass (Poa pratensis) infected by Ustilago striiformis (Stripe smut) or Urocystis agropyri (Flag smut) exhibits greater mortality than healthy plants during periods of water stress and is suggestive of decreased drought tolerance as a result of infection. The purpose of this study was to compare healthy Kentucky bluegrass ‘Merion’ and plants systemically infected by Ustilago striiformis or Urocystis agropyri for total, leaf and root growth, and for root‐shoot ratios in nutrient solution and in nutrient solution amended with polyethylene glycol to provide increasing levels of osmotically‐induced water stress. Infection by U. striiformis increased total and leaf dry weight, and decreased root weight and root‐shoot ratios of plants grown in nutrient solution. Plants infected by U. agropyri exhibited decreased total, leaf, and root weights, and root‐shoot ratios. Total, leaf, and root weights of healthy, U. striiformis‐and U. agropyri‐infected plants decreased, and root‐shoot ratios increased with decreasing osmotic potentials of nutrient solutions. The increases in total and leaf weights of U. striiformis‐infected plants compared with healthy plants grown in nutrient solution were lost as osmotic potentials decreased. Healthy plants maintained higher root‐shoot ratios than infected plants at all stress levels. The decreases in root‐shoot ratios of infected plants represent a morphological basis for reduced stress tolerance and subsequent increased mortality of infected plants during periods of water stress.

UFrocystis occulta . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Urocystis occulta . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Secale cereale ; occasionally recorded on other Gramineae including Agropyron caninum, A. inerme, Elymus canadensis, E. triticoides, Hordeum distichon, Lolium rigidum . DISEASE: Stripe or flag smut of rye. GEOGRAPHICAL DISTRIBUTION: Europe (except the Iberian peninsula), USSR, Turkey; Canada and USA; Australia. TRANSMISSION: Seed-borne. Rarely, soil-borne, but does not normally survive more than a few months in soil (34, 145; 30, 563; 16, 92; 15, 644).

A Method for Determining the Reactions of Wheat Breeding Lines to Flag Smut.

A Method for Determining the Reactions of Wheat Breeding Lines to Flag Smut.