K. J. Williams

Publications (3)4.97 Total impact

• Article: Development and use of an assay based on the polymerase chain reaction that differentiates the pathogens causing spot form and net form of net blotch of barley

  K. J. Williams, C. Smyl, A. Lichon, K. Y. Wong, H. Wallwork
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  ABSTRACT: Two forms of barley net blotch are caused by different formae of the fungus Pyrenophora teres and both are economically important pathogens. The spot form of the net blotch fungus (P. teres f. maculata) and the net form of the net blotch fungus (P. teres f. teres) cause the lesion types indicated by their disease names, although symptom overlap and similar spore morphology can make identification difficult. Randomly amplified polymorphic DNA fragments differentiated the two forms of Pyrenophora. Polymorphic bands were cloned and sequenced to develop specific primer sets. A simple assay based on the polymerase chain reaction was developed and can identify the Pyrenophora formae causing disease symptoms directly from infected plant tissues in a single multiplex reaction. The assay was validated using amplified fragment length polymorphism genotyping of isolates and was shown to be more accurate than reliance on symptom expression. This assay can now be used for routine diagnosis, epidemiological studies and resistance breeding, where correct identification of each pathogen is critical. Additional keywords Pyrenophora teres –AFLP–diagnosis
  Australasian Plant Pathology 04/2012; 30(1):37-44. · 0.84 Impact Factor
• Article: The application of species-specific assays based on the polymerase chain reaction to analyse Fusarium crown rot of durum wheat

  K. J. Williams, J. I. Dennis, C. Smyl, H. Wallwork
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  ABSTRACT: Crown rot of wheat in Australia is caused by species of Fusarium, particularly F pseudograminearum, formerly known as F. graminearum Group 1. Rapid assays are required to identify the species responsible for disease symptoms, especially those with similar morphology. Previously developed assays based on the polymerase chain reaction (PCR) were able to identify F. pseudograminearum, F. graminearum, F. culmorum and F. crookwellense isolates, but not F. acuminatum. To design novel F. acuminatum and F. pseudograminearum species-specific primer sets, randomly amplified polymorphic DNA profiles were amplified that differentiated F. acuminatum and F. pseudograminearum from the other species and polymorphic bands were cloned and sequenced. The specificity of the PCR assays was verified on 79 isolates from 12 different Fusarium species. For two isolates an apparent misidentification occurred using the F. pseudograminearum PCR assay. These isolates were fingerprinted using Amplified Fragment Length Polymorphism analysis, which showed that they had genotypes more similar to F. graminearum than F. pseudograminearum. The PCR-based assays were validated using seedlings infected with single or multiple isolates. A method was also devised to rapidly identify Fusarium species associated with crown rot symptoms on mature wheat stems by culturing the fungi and extracting DNA directly from infected tissue. This assay can be used for routine diagnosis and for epidemiological studies of this disease.
  Australasian Plant Pathology 04/2012; 31(2):119-127. · 0.84 Impact Factor
• Article: Identification and mapping of a gene conferring resistance to the spot form of net blotch (Pyrenophora teres f maculata) in barley

  K. J. Williams, A. Lichon, P. Gianquitto, J. M. Kretschmer, A. Karakousis, S. Manning, P. Langridge, H. Wallwork
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  ABSTRACT:  Spot form of net blotch (SFNB) (Pyrenophora teres f maculata) is an economically damaging foliar disease of barley in many of the world’s cereal growing areas. The development of SFNB-resistant cultivars may be accelerated through the use of molecular markers. A screen for SFNB resistance in 96 lines identified four new sources of resistance, including a feed variety, ‘Galleon’, for which a fully mapped doubled haploid population was available. Segregation data indicated SFNB resistance was conferred by a single gene in the ‘Galleon’בHaruna Nijo’ cross, positioned on the long arm of chromosome 7H. This gene is designated Rpt4 and is flanked by the RFLP loci Xpsr117(D) and Xcdo673 at distances of 6.9 cM and 25.9 cM, respectively. The marker Xpsr117(D) was validated using another population segregating for Rpt4, correctly predicting SFNB resistance with more than 90% accuracy.
  Theoretical and Applied Genetics 06/1999; 99(1):323-327. · 3.30 Impact Factor