Accumulation of Transcripts Abundance after Barley Inoculation with Cochliobolus sativus

Mohammad Imad Eddin Arabi,Antonious Al-Daoude,Amina Shoaib,Mohammad Jawhar 한국식물병리학회 2015 Plant Pathology Journal Vol.31 No.1

Spot blotch caused by the hemibiotrophic pathogenCochliobolus sativus has been the major yield-reducingfactor for barley production during the last decade. Monitoring transcriptional reorganization triggeredin response to this fungus is an essential first step forthe functional analysis of genes involved in the process. To characterize the defense responses initiated bybarley resistant and susceptible cultivars, a survey oftranscript abundance at early time points of C. sativusinoculation was conducted. A notable number of transcriptsexhibiting significant differential accumulationsin the resistant and susceptible cultivars were detectedcompared to the non-inoculated controls. At the p-valueof 0.0001, transcripts were divided into three generalcategories; defense, regulatory and unknown function,and the resistant cultivar had the greatest number ofcommon transcripts at different time points. Quantitiesof differentially accumulated gene transcripts inboth cultivars were identified at 24 h post infection, theapproximate time when the pathogen changes trophiclifestyles. The unique and common accumulated transcriptsmight be of considerable interest for enhancingeffective resistance to C. sativus.

Pathogenic Groups Identified Among Isolates of Rhynchosporium secalis

Mohammad Imad Eddin Arabi,Eyad Al-Shehadah,Mohammad Jawhar 한국식물병리학회 2010 Plant Pathology Journal Vol.26 No.3

Scald, caused by Rhynchosporium secalis has been the major yield-reducing factor for barley production during the last decade. In this study, pathogenic groups of R. secalis were identified to obtain a global picture of the assembly of isolates involved in Syrian populations which is essential for the development of scald-resistant barley cultivars. To identify a number of pathogenic groups, 49isolates collected over ten years from major barley growing areas in Syria were evaluated on five differential barley genotypes. Genotypes presented a continuous range of response from highly susceptible to moderately resistant, but none were immune to the disease. A cluster analysis placed isolates in six distinct differential pathogenic groups. Mean disease rating of 39.24% was the separation point between avirulent and virulent reactions. Isolate Rs46 exhibited distinct differential virulence patterns associated with high frequency across all genotypes. Hence, the data presented here provides crucial information for future selection of isolates to develop durable barley scald resistance.

A Simple Method for Assessing Severity of Common Root Rot on Barley

Mohammad Imad Eddin Arabi,Mohammad Jawhar 한국식물병리학회 2013 Plant Pathology Journal Vol.29 No.4

Common root rot caused by Cochliobolus sativus is a serious disease of barley. A simple and reliable method for assessing this disease would enhance our capacity in identifying resistance sources and developing resistant barley cultivars. In searching for such a method, a conidial suspension of C. sativus was dropped onto sterilized elongated subcrown internodes and incubated in sandwich filter paper using polyethylene transparent envelopes. Initial disease symptoms were easily detected after 48h of inoculation. Highly significant correlation coefficients were found in each experiment (A, B and C)between sandwich filter paper and seedling assays,indicating that this testing procedure was reliable. The method presented facilitates a rapid pre-selection under uniform conditions which is of importance from a breeder's point of view.

Alternative Measure for Assessing Incidence of Leaf Stripe on Barley

Mohammad Imad Eddin Arabi,Mohammad Jawhar 한국식물병리학회 2012 Plant Pathology Journal Vol.28 No.2

Pyrenophora graminea, the causal agent of leaf stripe disease, is an economically important pathogen of barley found worldwide. It is critical to clearly define and standardize the leaf stripe assessment methods to avoid subjectivity and variability between assessors. Therefore, in this study, a comparison between the proportion of diseased plants (DP) and the proportion of diseased leaves (DL) per plant was investigated. Disease assessments were made visually at multiple sample sites in artificially and naturally inoculated research and production fields during four growing seasons. There were significant differences (P = 0.001) among cultivars in mean DP and DL averages, which are consistently higher in susceptible barley. However, DP values increased linearly as DL increased. The slopes and intercepts of the DP-DL relationship were consistent over the four growing seasons. This result might make a significant contribution for leaf stripe assessment in barley breeding programme.

Vegetative Compatibility Groups and Virulence Variation Among Isolates of Pyrenophora graminea

Mohammad Imad Eddin Arabi,Mohammad Jawhar 한국식물병리학회 2011 Plant Pathology Journal Vol.27 No.2

Pyrenophora graminea, the causal agent of leaf stripe disease, is an economically important pathogen of barley found worldwide. Forty-four isolates of diverse geographical origin within Syria were grouped into vegetative compatibility groups (VCGs) by demonstrating heterokaryosis by complementation tests using nitrate nonutilizing (nit) mutants. All isolates were grouped into three VCGs-1-A, 1-B and 1-C. No self-incompatibility was observed in any of the isolates tested. VCG 1-A was the most common group within growing regions in Syria and proved to be the most virulent of the VCGs identified. These data indicate that the level of virulence in P. graminea is related to VCG.

Greenhouse Method for Assessing Spot Blotch Resistance in Barley

Mohammad Imad Eddin Arabi,Mohammad Jawhar 한국식물병리학회 2010 Plant Pathology Journal Vol.26 No.4

New sources of barley (Hordeum vulgare L.) resistant to spot blotch, caused by Cochliobolus sativus, are needed to provide effective resistance because of the rapid change pathotype patterns of C. sativus in fields. The purposes of our study were to develop a method to screen barley for resistance to spot blotch disease and then use this methodology to screen barley genotypes for resistance to the major virulent pathotype Pt4 in barley populations in Syria. A transparent tape method,in which a conidial suspension of C. sativus was dropped onto transparent tape and placed, treated-side down, on the second leaf surface of barley plants. Disease symptoms of fungus were easily detected on the leaves covered by the transparent tape after 48h of inoculation. The transparent tape method was repeatable and the disease scores obtained were correlated (r = 0.91, P = 0.001) with those obtained by the seedling assay. This method may be beneficial in various plant pathology breeding programs.

Greenhouse Method for Assessing Spot Blotch Resistance in Barley

Arabi, Mohammad Imad Eddin,Jawhar, Mohammad The Korean Society of Plant Pathology 2010 Plant Pathology Journal Vol.26 No.4

New sources of barley (Hordeum vulgare L.) resistant to spot blotch, caused by Cochliobolus sativus, are needed to provide effective resistance because of the rapid change pathotype patterns of C. sativus in fields. The purposes of our study were to develop a method to screen barley for resistance to spot blotch disease and then use this methodology to screen barley genotypes for resistance to the major virulent pathotype Pt4 in barley populations in Syria. A transparent tape method, in which a conidial suspension of C. sativus was dropped onto transparent tape and placed, treated-side down, on the second leaf surface of barley plants. Disease symptoms of fungus were easily detected on the leaves covered by the transparent tape after 48h of inoculation. The transparent tape method was repeatable and the disease scores obtained were correlated (r = 0.91, P = 0.001) with those obtained by the seedling assay. This method may be beneficial in various plant pathology breeding programs.

A Simple Method for Assessing Severity of Common Root Rot on Barley

Arabi, Mohammad Imad Eddin,Jawhar, Mohammad The Korean Society of Plant Pathology 2013 Plant Pathology Journal Vol.29 No.4

Common root rot caused by Cochliobolus sativus is a serious disease of barley. A simple and reliable method for assessing this disease would enhance our capacity in identifying resistance sources and developing resistant barley cultivars. In searching for such a method, a conidial suspension of C. sativus was dropped onto sterilized elongated subcrown internodes and incubated in sandwich filter paper using polyethylene transparent envelopes. Initial disease symptoms were easily detected after 48h of inoculation. Highly significant correlation coefficients were found in each experiment (A, B and C) between sandwich filter paper and seedling assays, indicating that this testing procedure was reliable. The method presented facilitates a rapid pre-selection under uniform conditions which is of importance from a breeder's point of view.

Accumulation of Transcripts Abundance after Barley Inoculation with Cochliobolus sativus

Arabi, Mohammad Imad Eddin,AL-Daoude, Antonious,Shoaib, Amina,Jawhar, Mohammad The Korean Society of Plant Pathology 2015 Plant Pathology Journal Vol.31 No.1

Spot blotch caused by the hemibiotrophic pathogen Cochliobolus sativus has been the major yield-reducing factor for barley production during the last decade. Monitoring transcriptional reorganization triggered in response to this fungus is an essential first step for the functional analysis of genes involved in the process. To characterize the defense responses initiated by barley resistant and susceptible cultivars, a survey of transcript abundance at early time points of C. sativus inoculation was conducted. A notable number of transcripts exhibiting significant differential accumulations in the resistant and susceptible cultivars were detected compared to the non-inoculated controls. At the p-value of 0.0001, transcripts were divided into three general categories; defense, regulatory and unknown function, and the resistant cultivar had the greatest number of common transcripts at different time points. Quantities of differentially accumulated gene transcripts in both cultivars were identified at 24 h post infection, the approximate time when the pathogen changes trophic lifestyles. The unique and common accumulated transcripts might be of considerable interest for enhancing effective resistance to C. sativus.

Pathogenic Groups Identified Among Isolates of Rhynchosporium secalis

Arabi, Mohammad Imad Eddin,Al-Shehadah, Eyad,Jawhar, Mohammad The Korean Society of Plant Pathology 2010 Plant Pathology Journal Vol.26 No.3

Scald, caused by Rhynchosporium secalis has been the major yield-reducing factor for barley production during the last decade. In this study, pathogenic groups of R. secalis were identified to obtain a global picture of the assembly of isolates involved in Syrian populations which is essential for the development of scald-resistant barley cultivars. To identify a number of pathogenic groups, 49 isolates collected over ten years from major barley growing areas in Syria were evaluated on five differential barley genotypes. Genotypes presented a continuous range of response from highly susceptible to moderately resistant, but none were immune to the disease. A cluster analysis placed isolates in six distinct differential pathogenic groups. Mean disease rating of 39.24% was the separation point between avirulent and virulent reactions. Isolate Rs46 exhibited distinct differential virulence patterns associated with high frequency across all genotypes. Hence, the data presented here provides crucial information for future selection of isolates to develop durable barley scald resistance.