scholarly journals First Report of Spot Type of Barley Net Blotch Caused by Pyrenophora teres f. sp. maculata in Uruguay

Plant Disease ◽  
2004 ◽  
Vol 88 (10) ◽  
pp. 1162-1162
Author(s):  
S. A. Pereyra ◽  
S. E. Germán
Keyword(s):  
North Dakota ◽  
Tween 20 ◽  
Pyrenophora Teres ◽  
Sterile Water ◽  
Net Blotch ◽  
First Report ◽  
Production Region ◽  
Resistant Infection ◽  
Infection Types ◽  
Spot Type

In September 2003, leaves exhibiting spot-type lesions similar to those produced by Cochliobolus sativus Drechs. ex Dastur were widely observed in six commercial barley crops of cvs. Norteña Daymán, Norteña Carumbé, and MUSA 936 in Soriano and Río Negro provinces, the main barley production region in western Uruguay. Spot lesions were tan to dark brown, circular to elliptical, and 3 to 10 mm in diameter. Larger lesions were surrounded by a chlorotic margin of varying width. Affected leaf pieces (10 to 15) from each field were placed in a moist chamber for 2 days to promote sporulation. A fungus identified morphologically as Pyrenophora teres (Died.) Drechs. (1) was consistently isolated from infected leaves. However, symptoms did not correspond to the net-type lesions of net blotch commonly produced by P. teres f. sp. teres in Uruguay. Three monoconidial cultures were obtained by transferring single conidia to potato dextrose agar and then to 10% V8 juice agar and incubated at 20 to 22°C with a 12-h photoperiod for 10 days. Adding sterile water to each plate and gently rubbing the surface with a microscope slide prepared inoculum for pathogenicity tests. Conidia concentration was adjusted to 1 × 104 conidia per ml. Sixty-eight barley genotypes from Uruguay, ICARDA/CIMMYT, and North Dakota were grown in the greenhouse for 2 weeks at 20 to 22°C with a 14-h photoperiod. For each monoconidial isolate, three seedlings of each genotype were inoculated at the three-leaf stage 15 to 16 days after seeding with 0.4 ml of the inoculum suspension with an airbrush inoculator. A drop of Tween 20 was added per 40 ml of inoculum suspension. One set of each genotype was inoculated with sterile water as a control. Seedlings were placed in a dew chamber at 20°C and 100% relative humidity in the dark for 24 h and then returned to prior conditions. The first lesions developed after 7 to 9 days. Leaves two and three of the plants were visually rated for disease (3) 13 days after inoculation. Control plants were disease free. The most susceptible reactions were observed on cvs. Norteña Daymán, MUSA 936, and line CLE 230 (Uruguay). Symptoms were similar in shape and size to those observed in the fields. The most resistant infection types were observed on several Uruguayan and North Dakota advanced lines. The fungus was consistently reisolated from inoculated plants. On the basis of morphology and symptoms produced, the pathogen was identified (2) as P. teres. f. sp. maculata Smedeg. To our knowledge, this is the first report of this fungus causing spot-like symptoms of net blotch in Uruguay. References: (1) M. B. Ellis. Dematiaceous hyphomycetes, CABI, Oxon, UK, 1971. (2) V. Smedergaard-Petersen. Pages 124–144 in: R. Vet. Agr. Univ. Yearbook, Copenhagen, 1971. (3) A. Tekauz. Can. J. Plant Pathol.7:181, 1985.

scholarly journals First Report of Cladosporium Leaf Spot of Spinach Caused by Cladosporium variabile in the Winter Spinach Production Region of California and Arizona

Plant Disease ◽  
2012 ◽  
Vol 96 (7) ◽  
pp. 1071-1071 ◽  
Author(s):  
L. J. du Toit ◽  
M. L. Derie
Keyword(s):  
Leaf Spot ◽  
The United States ◽  
Tween 20 ◽  
Sterile Water ◽  
Single Spore ◽  
Imperial Valley ◽  
First Report ◽  
Production Region ◽  
Plastic Bags ◽  
Seed Crops

In December 2011, symptoms typical of Cladosporium leaf spot caused by Cladosporium variabile (4) were observed in organic “baby leaf” spinach (Spinacia oleracea) crops of the cultivars Amazon, Missouri, Tasman, and Tonga in the Imperial Valley (Imperial County, CA and Yuma County, AZ). Leaves had small, circular lesions (1 to 3 mm in diameter), some of which had progressed to necrotic, bleached lesions surrounded by a thin dark margin. The incidence of symptoms in affected crops was ≤20%. Fungal isolates resembling C. variabile were recovered by surfacesterilizing sections (5 mm2) of symptomatic leaf tissue in 0.6% NaOCl, triple-rinsing the sections in sterile water, and plating the sections onto water agar and potato dextrose agar amended with 100 ppm chloramphenicol (cPDA). Single-spore transfers made onto cPDA were maintained at 24 ± 2°C with a natural day/night cycle. Each isolate produced slow growing cultures consisting of dense masses of dark conidiophores (≤350 μm long) with chains of up to three dematiaceous (olive) conidia, and almost no mycelium. Torulose (coiled) aerial hyphae developed from the apices of conidiophores after 5 to 7 days, and distinguished the isolates as C. variabile, not C. macrocarpum (2,4). Pathogenicity was tested for each of six single-spore isolates using 36-dayold plants of the spinach cultivar Carmel. The plants were enclosed in clear plastic bags overnight and inoculated the next day with the isolates of C. variabile by atomizing approximately 30 ml of a spore suspension (1.0 × 106 conidia/ml in sterile water amended with 0.01% Tween 20) of the appropriate isolate onto the upper and lower leaf surfaces of each of five plants/isolate. Five control plants were inoculated similarly with sterile water + 0.01% Tween 20. The plants were resealed in plastic bags for 72 h and then placed on a greenhouse bench. Pinpoint, sunken lesions developed within 4 to 7 days on the leaves of plants inoculated with each of the six test isolates. Lesions developed into dry, circular spots typical of Cladosporium leaf spot. Symptoms were not observed on control plants. After 20 days, C. variabile was reisolated from lesions caused by all six isolates, but not from control plants. Although Cladosporium leaf spot has been reported in the Salinas Valley of California (4), to our knowledge, this is the first report of the disease on spinach crops in the Imperial Valley of California and Arizona, the primary winter, fresh market spinach production region of the United States. Inoculum of C. variabile may have been introduced to this region on spinach seed lots (3), because even seed infestation levels <0.1% could lead to seed transmission (1) under the dense planting populations (≤9 million seeds/ha) and overhead irrigation typical of “baby leaf” spinach crops in this region. Fungicides can be used to manage Cladosporium leaf spot in conventional spinach crops (1), but management in certified organic crops may be more challenging. References: (1) L. J. du Toit et al. Fung. Nemat. Tests 59:V115, 2004. (2) M. B. Ellis. Page 315 in: Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Surrey, England, 1971. (3) P. Hernandez-Perez. Page 79 in: Management of Seedborne Stemphylium botryosum and Cladosporium variabile Causing Leaf Spot of Spinach Seed Crops in Western Washington, MS thesis, Pullman, WA, 2005. (4) P. Hernandez-Perez and L. J. du Toit. Plant Dis. 90:137, 2006.

scholarly journals Identification of Pyrenophora teres f. maculata, Causal Agent of Spot Type Net Blotch of Barley in North Dakota

Plant Disease ◽  
2010 ◽  
Vol 94 (4) ◽  
pp. 480-480 ◽  
Author(s):  
Z. H. Liu ◽  
T. L. Friesen
Keyword(s):  
North Dakota ◽  
Leaf Tissue ◽  
Causal Agent ◽  
Tan Spot ◽  
Pathogenicity Test ◽  
Pyrenophora Teres ◽  
Net Blotch ◽  
Hordeum Vulgare L ◽  
Single Spore ◽  
Spot Type

Net blotch of barley (Hordeum vulgare L.) caused by the fungus Pyrenophora teres (anamorph Drechslera teres) is found in two forms, net form net blotch (NFNB) and spot form net blotch (SFNB). When inoculated on susceptible varieties, P. teres f. teres produces lesions with a characteristic net-like pattern surrounded by necrosis or chlorosis (NFNB), whereas P. teres f. maculata produces lesions consisting of spots surrounded by necrosis or chlorosis (SFNB). Recently, epidemics of SFNB have occurred throughout the world (4). Currently, net blotch is a significant foliar disease of barley in the North Dakota-Northwestern Minnesota agricultural region, a leading barley-production area. Diseased barley leaf tissue was collected annually from 2004 to 2008 in Fargo and Langdon, ND. Diseased leaves were incubated to promote sporulation. Ten single-spore isolates of P. teres collected from each location each year were tested for virulence by inoculation on 20 commonly used barley net blotch differential lines. Among the 100 isolates collected, one isolate collected in Fargo in 2006 (FGOH06Pt-8) and one isolate collected in Langdon in 2008 (LDNH08Pt-4) were identified as P. teres f. maculata due to their induction of spot-type lesions across the differential set. Conidial morphology of the two isolates was similar to P. teres f. teres isolates. A pathogenicity test of all isolates was performed on regional barley cvs. Tradition, Robust, and Lacey as well as barley lines Rika and Kombar (1) as previously described (3). The net form isolate 0-1 and spot form isolate DEN2.6 (obtained from B. Steffenson, University of Minnesota) were used as controls. The P. teres f. teres isolate 0-1 produced typical net type symptoms on all barley lines except the resistant line Rika, in which only small, dark spots were observed. DEN2.6 produced pin-point spot-like lesions with an extensive yellow halo on Robust, Lacey, Rika, and Kombar, but without chlorosis on Tradition. The two newly identified isolates induced elliptical spot-type lesions measuring 3 × 6 mm, larger than those produced by P. teres f. maculata isolate DEN 2.6, suggesting a higher level of virulence. We constructed a neighbor-joining phylogenetic tree using ClustalW2 ( http://www.ebi.ac.uk/ ) based on sequence identity of the internal transcribed spacer (ITS) region from 0-1 (GenBank No. GU014819), DEN2.6 (GenBank No. GU014820), FGOH06Pt-8 (GenBank No. GU014821), and LDNH08Pt-4 (GenBank No. GU014822) as well as P. teres f. maculata, P. teres f. teres, and P. tritici-repentis (causal agent of tan spot of wheat) accessions obtained from GenBank (2). All P. teres isolates clustered together and were clearly separated from the P. tritici-repentis cluster. Isolates FGOH06Pt-8 and LDNH08Pt-4 had identical ITS sequences and differed from DEN2.6 by only a single nucleotide. To our knowledge, this is the first report of P. teres f. maculata in North Dakota. Resistance to SFNB should now be considered in local barley breeding programs and cultivar releases. Reference: (1) M. Abu Qamar. Theor. Appl. Genet. 117:1261, 2008. (2) R. M. Andrie et al. Fungal Genet. Biol. 45:363, 2008. (3) Z. Lai et al. Fungal Genet. Biol. 44:323, 2007. (4) M. S. McLean et al. Crop Pasture Sci. 60:303, 2009.

scholarly journals First Report of Spot Form Net Blotch Caused by Pyrenophora teres f. maculata on Barley in the Mon-Dak Area of the United States

Plant Disease ◽  
2013 ◽  
Vol 97 (1) ◽  
pp. 143-143 ◽  
Author(s):  
R. T. Lartey ◽  
T. C. Caesar-TonThat ◽  
A. J. Caesar ◽  
U. M. Sainju ◽  
R. G. Evans
Keyword(s):  
North Dakota ◽  
Its Region ◽  
The United States ◽  
Northern Great Plains ◽  
Pathogenicity Test ◽  
Pyrenophora Teres ◽  
Net Blotch ◽  
Morphological Examination ◽  
First Report ◽  
Barley Cultivars

Pyrenophora teres Drechs. causes net blotch of barley, a common foliar disease in cultivation zones around the world. The disease occurs in two forms, namely a net form net blotch (NFNB) caused by P. teres f. teres and a spot form net blotch (SFNB) caused by P. teres f. maculata. As in other parts of the northern Great Plains, in the Mon-Dak area (western North Dakota and eastern Montana), NFNB is prevalent. SFNB was first reported in western Montana in 1983 (1) and more recently in eastern North Dakota in 2010 (3) but not in the Mon-Dak area. In the summer of 2011, unusual spot lesions that were surrounded by necrosis or chlorosis were observed on different barley cultivars in fields at Williston, ND, Nesson Valley, ND, and Sidney, MT areas. Diseased leaves from various barley cvs. from the three locations were transferred to water agar and incubated at room temperature for 24 h to induce sporulation. Morphological examination of conidia (45 to 169 × 15 to 21 μm) did not show significant differences from a known isolate of P. teres f. teres 0-1 (provided by Tim Friesen, ARS, Fargo, ND). For pathogenicity testing, six 14-day-old plants of barley cv. Tradition were sprayed until runoff with a 2,000 spore/ml suspension of two isolates from each location and the control P. teres f. maculata isolate DEN2.6 (provided by Tim Friesen). Plants were incubated first in a lighted humidity chamber for 24 h and then in a greenhouse for 7 days at 21°C. Regardless of inoculum source, spot lesions surrounded by necrosis or chlorosis, typical of SFNB, appeared on the inoculated leaves within 7 days. Fungi isolated from symptomatic leaves were identified as P. teres and the morphology of the conidia was undistinguishable from those of P. teres f. teres. All control plants which were sprayed with sterile distilled water were symptomless. The pathogenicity test was repeated. Rapid PCR detection and amplicon sequencing (2) of the internal transcribed spacer (ITS) region of ribosomal genes was performed on field and pathogenicity test leaf lesion samples to confirm the presence of P. teres f. maculata. DNA templates were prepared using the Extract-N-Amp Plant PCR Kits (Sigma Chemical Co., St. Louis, MO) and subjected to PCR using ITS1 and ITS4 primers. Amplicons were then purified and sequenced. The 585-bp nucleotide sequences of P. teres f. maculata from Mon-Dak area were submitted to GenBank under accession nos. PtmNES1 (JX187587), PtmSDY1 (JX187588), PtmSDY2 (JX187589), and PtmWIL1 (JX187590). The sequences from the four locations shared 100% similarity and also with P. teres f. maculata (EF452471) from GenBank while showing 10 nucleotide differences (99% similarity) with P. teres f. teres (EF452472).The results represent first report of SFNB in the Mon-Dak. Barley is one of the most important crops in the area. Resistance of the NFNB and SFNB of barley are controlled by different genes (4). Based on this report, SFNB therefore have to be considered in selection of barley cultivars for cultivation in the area. References: (1) H. E Bockelman et al. Plant Dis. 67:696, 1983. (2) R. T. Lartey et al. J. Sugar Beet Res. 40:1, 2003. (3) Z. H. Liu and T. L. Friesen. Plant Dis. 94:480, 2010. (4) O. M. Manninen et al. Genome. 46:1564, 2006.

scholarly journals First Report of Nigrospora osmanthi Causing Leaf Spot on Tartary Buckwheat in China

Plant Disease ◽  
2020 ◽  
Author(s):  
Quan Shen ◽  
Xixu Peng ◽  
Feng He ◽  
Shaoqing Li ◽  
Zuyin Xiao ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Leaf Spot ◽  
Plant Pathogens ◽  
Hunan Province ◽  
Tartary Buckwheat ◽  
Tween 20 ◽  
Pathogenicity Test ◽  
Conidial Suspension ◽  
Sterile Water ◽  
First Report

Buckwheat (Fagopyrum tataricum) is a traditional short-season pseudocereal crop originating in southwest China and is cultivated around the world. Antioxidative substances in buckwheat have been shown to provide many potential cardiovascular health benefits. Between August and November in 2019, a leaf spot was found in several Tartary buckwheat cv. Pinku1 fields in Xiangxiang County, Hunan Province, China. The disease occurred throughout the growth cycle of buckwheat after leaves emerged, and disease incidence was approximately 50 to 60%. Initially infected leaves developed a few round lesions, light yellow to light brown spots. Several days later, lesions began to enlarge with reddish brown borders, and eventually withered and fell off. Thirty lesions (2×2 mm) collected from three locations with ten leaves in each location were sterilized in 70% ethanol for 10 sec, in 2% sodium hypochlorite for 30 sec, rinsed in sterile water for three times, dried on sterilized filter paper, and placed on a potato dextrose PDA with lactic acid (3 ml/L), and incubated at 28°C in the dark for 3 to 5 days. Fungal colonies were initially white and later turned black with the onset ofsporulation. Conidia were single-celled, black, smooth, spherical to subspherical, and measured 9.2 to 15.6 µm long, and 7.1 to 11.6 µm wide (n=30). Each conidium was terminal and borne on a hyaline vesicle at the tip of conidiophores. Morphologically, the fungus was identified as Nigrospora osmanthi (Wang et al. 2017). Identification was confirmed by amplifying and sequencing the ITS region, and translation elongation factor 1-alpha (TEF1-α) and partial beta-tublin (TUB2) genes using primers ITS1/ITS4 (Mills et al. 1992), EF1-728F/EF-2 (Carbone and Kohn 1999; O’Donnell et al. 1998) and Bt-2a/Bt-2b (Glass et al. 1995), respectively. BLAST searches in GenBank indicated the ITS (MT860338), TUB2 (MT882054) and TEF1-α (MT882055) sequences had 99.80%, 99% and 100% similarity to sequences KX986010.1, KY019461.1 and KY019421.1 of Nigrospora osmanthi ex-type strain CGMCC 3.18126, respectively. A neighbor-joining phylogenetic tree constructed using MEGA7.0 with 1,000 bootstraps based on the concatenated nucleotide sequences of the three genes indicated that our isolate was closely related to N. osmanthi. Pathogenicity test was performed using leaves of healthy F. tataricum plants. The conidial suspension (1 × 106 conidia/ml) collected from PDA cultures with 0.05% Tween 20 buffer was used for inoculation by spraying leaves of potted 20-day-old Tartary buckwheat cv. Pinku1. Five leaves of each plant were inoculated with spore suspensions (1 ml per leaf). An equal number of control leaves were sprayed with sterile water to serve as a control. The treated plants were kept in a greenhouse at 28°C and 80% relative humidity for 24 h, and then transferred to natural conditions with temperature ranging from 22 to 30°C and relative humidity ranging from 50 to 60%. Five days later, all N. osmanthi-inoculated leaves developed leaf spot symptoms similar to those observed in the field, whereas control leaves remained healthy. N. osmanthi was re-isolated from twelve infected leaves with frequency of 100%, fulfilling Koch’s postulates. The genus Nigrospora has been regarded by many scholars as plant pathogens (Fukushima et al. 1998) and N. osmanthi is a known leaf blight pathogen for Stenotaphrum secundatum (Mei et al. 2019) and Ficus pandurata (Liu et al. 2019) but has not been reported on F. tataricum. Nigrospora sphaerica was also detected in vegetative buds of healthy Fagopyrum esculentum Moench (Jain et al. 2012). To our knowledge, this is the first report of N. osmanthi causing leaf spot on F. tataricum in China and worldwide. Appropriate strategies should be developed to manage this disease.

SOURCES OF RESISTANCE IN BARLEY TO PYRENOPHORA TERES

1965 ◽  
Vol 45 (2) ◽  
pp. 189-193 ◽  
Author(s):  
K. W. Buchannon ◽  
W. C. McDonald
Keyword(s):  
North Dakota ◽  
Quality Characteristics ◽  
Seedling Stage ◽  
Malting Quality ◽  
Western Canada ◽  
Pyrenophora Teres ◽  
Net Blotch ◽  
Sources Of Resistance ◽  
Highly Pathogenic ◽  
Resistant Varieties

The reaction to infection by Pyrenophora teres Drechs., the incitant of net blotch of barley, was determined for 6,174 varieties in the U.S.D.A. World Barley Collection. Forty varieties, seventeen of them from Ethiopia, were resistant in the seedling stage to a highly pathogenic strain of the fungus prevalent in Western Canada and to composites of isolates from Manitoba, Saskatchewan, Alberta, Ontario, North Dakota, California, and Mexico. They were also resistant in the field at three locations in Western Canada. Agronomic and malting quality characteristics for the resistant varieties were also recorded.

scholarly journals Identification and chromosomal location of major genes for resistance to Pyrenophora teres in a doubled-haploid barley population

Genome ◽  
2006 ◽  
Vol 49 (7) ◽  
pp. 855-859 ◽  
Author(s):  
T L Friesen ◽  
J D Faris ◽  
Z Lai ◽  
B J Steffenson
Keyword(s):  
Doubled Haploid ◽  
Doubled Haploid Population ◽  
Pyrenophora Teres ◽  
Net Blotch ◽  
Seedling Resistance ◽  
Drechslera Teres ◽  
Haploid Population ◽  
Barley Population ◽  
Spot Type ◽  
Simple Sequence

Net blotch, caused by Pyrenophora teres, is one of the most economically important diseases of barley worldwide. Here, we used a barley doubled-haploid population derived from the lines SM89010 and Q21861 to identify major quantitative trait loci (QTLs) associated with seedling resistance to P. teres f. teres (net-type net blotch (NTNB)) and P. teres f. maculata (spot-type net blotch (STNB)). A map consisting of simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers was used to identify chromosome locations of resistance loci. Major QTLs for NTNB and STNB resistance were located on chromosomes 6H and 4H, respectively. The 6H locus (NTNB) accounted for as much as 89% of the disease variation, whereas the 4H locus (STNB resistance) accounted for 64%. The markers closely linked to the resistance gene loci will be useful for marker-assisted selection.Key words: disease resistance, Drechslera teres, molecular markers.

EFFECT OF TILT ON SEVERITY OF SPOT-TYPE NET BLOTCH, GRAIN YIELD AND YIELD COMPONENTS IN BARLEY

1990 ◽  
Vol 70 (2) ◽  
pp. 473-480 ◽  
Author(s):  
C. G. J. VAN DEN BERG ◽  
B. G. ROSSNAGEL
Keyword(s):  
Grain Yield ◽  
Yield Components ◽  
Kernel Weight ◽  
Growth Stages ◽  
Pyrenophora Teres ◽  
Susceptible Cultivar ◽  
Net Blotch ◽  
Single Application ◽  
Yield And Yield Components ◽  
Spot Type

Spot-type net blotch, incited by Pyrenophora teres f. maculata has become widespread in Saskatchewan. This study was conducted to evaluate the effect of the fungicide Tilt (propiconazole) on the severity of spot-type net blotch, grain yield and yield components in spring barley. The susceptible cultivar Elrose was subjected to five schedules of foliar application of Tilt at Medstead, Shellbrook and Saskatoon, Saskatchewan in 1985 and 1986. The moderately susceptible cultivar Argyle was included in the experiments conducted in 1986. Results show that Tilt controlled spot-type net blotch in Elrose. However, the effective period was limited. A single application did not control spot-type net blotch in cases with rapid disease development. Application of Tilt at Zadoks growth stages 31 and 49 would be required to provide reliable control in a susceptible cultivar. Control of spot-type net blotch increased grain yield. A single application of Tilt increased grain yield up to 23% over the untreated control. In most cases, a double application of Tilt did not increase grain yield over a timely single application. Increased grain yield was associated with increased kernel weight. The correlation coefficient between grain yield and kernel weight ranged from 0.82 to 0.88. Tilt had no effect on a healthy crop of Elrose and the moderately susceptible cultivar Argyle.Key words: Pyrenophora teres f. maculata, Hordeum vulgare L., propiconazole, barley

scholarly journals First Report of Pyrenophora teres f. maculata the Cause of Spot Form Net Blotch of Barley in Idaho

Plant Disease ◽  
2015 ◽  
Vol 99 (12) ◽  
pp. 1860 ◽  
Author(s):  
J. M. Marshall ◽  
K. Kinzer ◽  
R. S. Brueggeman
Keyword(s):  
Pyrenophora Teres ◽  
Net Blotch ◽  
First Report

scholarly journals Virulence Profile and Genetic Structure of a North Dakota Population of Pyrenophora teres f. teres, the Causal Agent of Net Form Net Blotch of Barley

2012 ◽  
Vol 102 (5) ◽  
pp. 539-546 ◽  
Author(s):  
Z. H. Liu ◽  
S. Zhong ◽  
A. K. Stasko ◽  
M. C. Edwards ◽  
T. L. Friesen
Keyword(s):  
North Dakota ◽  
Gene Diversity ◽  
Random Mating ◽  
Common Source ◽  
Pyrenophora Teres ◽  
Net Blotch ◽  
Seedling Resistance ◽  
Wide Range ◽  
Significant Difference ◽  
Net Form Net Blotch

A Pyrenophora teres f. teres population in North Dakota was analyzed for virulence variation and genetic diversity using 75 monospore isolates that were collected across a 4-year period (2004 to 2007) from two North Dakota State University agricultural experiment stations at Fargo and Langdon. Pathogenicity tests by inoculation onto 22 barley differential lines at seedling stage revealed 49 pathotypes, indicating a wide range of pathogenic diversity. Two-way analysis of variance of disease ratings revealed a significant difference in the virulence among isolates and in the resistance among barley lines, as well as in the interactions between the two. ‘CI5791’, ‘Algerian’, and ‘Heartland’ were three barley lines showing a high level of seedling resistance to all North Dakota isolates tested; however, many previously reported resistance genes have been overcome. Forty multilocus genotypes were identified from this set of isolates by genotyping at 13 simple-sequence repeat loci. High percentages of clonal cultures were detected in the samplings from 2005 and 2007 in Fargo and 2005 in Langdon. Using a clone-corrected sample set, the mean gene diversity (h) was estimated to be 0.58, approximately the same for both locations. The calculated Wright's FST value is small (0.11) but was significantly >0, indicating a significant differentiation between the Fargo and Langdon populations. In the gametic disequilibrium test, only 3 of 78 possible pairwise comparisons over all isolates showed significant (P < 0.05) nonrandom association, suggesting a random mating mode. Our results suggest that the populations from the two locations are derived from a common source and undergo frequent recombination. This research provides important information for barley breeders regarding development and deployment of cultivars with resistance to net form net blotch in this region.

scholarly journals A Comparative Study of Pyrenophora Teres Drechs. F. Teres and Pyrenophora Teres Drechs. F. Maculata Smedeg. Cause of "Net" and "Spot" Type Net Blotch Respectively on New Zealand Barley

2021 ◽  
Author(s):  
◽  
Daphne Geraldine Carvalho
Keyword(s):  
New Zealand ◽  
Comparative Study ◽  
Growth Rates ◽  
Morphological Difference ◽  
Pyrenophora Teres ◽  
Net Blotch ◽  
Drechslera Teres ◽  
Necrotic Spots ◽  
Spot Type ◽  
Number Of Cells

<p>Net blotch is caused by Pyrenophora teres Drechs. (stat. conid. Drechslera teres (Sacc.) Shoem., syn. Helminthosporium teres Sacc). P. teres produces symptoms which appear initially as small necrotic spots and streaks on the leaf. These increase to produce the characteristic net-like symptoms, which have given rise to the name net blotch. Sometimes, lesions develop from small necrotic spots, to form elliptical lesions. This is the "spot" type of P. teres and was first noticed in 1967 in isolates from North America, Mexico, Israel and Holland. It was thought that these isolates were mutants of P. teres. Since 1969 however, other workers have reported similar observations widely occurring in Norway, Denmark and Finland. Based on minor morphological differences, Ito and Kuribayashi proposed a new species, called P. japonica. Smedegård-Petersen disagreed, and showed that the spot-producing isolate represents a deviating type of P. teres, only differing from the usual "net" type in the symptoms induced on barley plants. He based his reasoning on morphological, cultural and genetical investigations. Consequently, Smedegård-Petersen described two new forms of the fungus, Pyrenophora teres Drechs. f. teres Smedeg., which produces the usual net lesions, and Pyrenophora teres Drechs. f. maculata Smedeg., which produces well defined dark brown circular or elliptical lesions without netting. The aim of the research undertaken in the present study was to conduct a comparative study on the morphology and fitness of a range of New Zealand "net" and "spot" type isolates. An attempt was also made at crossing a "net" type with a "spot" type. Although Smedegård-Petersen had stated that there was no morphological difference between the "net" and "spot" types, this project was undertaken because no research had been done on New Zealand isolates. Furthermore, different features were studied using different methods not used by other workers in studying P. teres. The only morphological difference that was distinctive was that the "spot" types of P. teres formed coremial strands, which were fan-like in morphology, which produced conidia in culture, and the "net" types did not. There was no way to tell the "net" isolates apart from the "spot" isolates, based on conidia colour, length, width, volume or the number of cells per conidium. One fact that did emerge, was that the longest conidia had the greatest number of cells per conidium and the reverse was also true. The germination of monoconidial isolates showed that there were no major differences in branching between the two types of P. teres. However, it was revealed that two germ tubes were capable of emerging from one cell in the "spot" isolates. All cells in a conidium in both the "net" and "spot" types were able to germinate, cells that germinated tended to be at opposite ends, and the first cell to germinate in a conidium was usually the cell at the hilum. Examination of the growth rates showed that there were no significant differences in the growth rates of the "net" and "spot" types when grown on MEA+B. The "spot" types were able to penetrate cellulose faster than the "net" types and hence may produce cellulose faster as well. ANT148, which had previously been an unknown type, was proved to be a "spot" type in the pathogenicity tests. It may have been the source of the New Zealand "spot" type inoculum because the seed it came from was imported into New Zealand in 1984, two years prior to the discovery of the "spot" type of P. teres in the South Island. Both forms of P. teres penetrated the leaf through the epidermal cell wall, and occasionally entered through the stomata. Even though the "spot" type may be present inside the leaf, the symptoms are not usually manifested until later, compared with the "net" type where the symptoms tend to be an indication of the amount of hyphae present in the leaf. In the screening of the progeny from the crossing, the "spot" type of P. teres had lost up to 78.9% of its resistance to triadimenol and flutriafol, when compared to the sensitivity tests carried out in 1986 and 1987. It is hypothesised that 13Y, the "net" type is dominant, and the "spot" type, KF2, recessive, as none of the progeny had any resistance to triadimenol or flutriafol, after undergoing somatic recombination. It was concluded that the "spot" and "net" types are two types of the same species, and there was not enough evidence to suggest otherwise. Further studies should be done, using more current isolates of the "net" and "spot" types of P. teres, and the old D. japonica isolates from New Zealand, to establish if the cultures identified as D. japonica, are different in any way.</p>

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