ARS | Publication request: Occurrence of spot-form net blotch of barley in the Mon-Dak area of the US

Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2012
Publication Date: July 18, 2012
Citation: Lartey, R.T., Evans, R.G., Caesar, T., Caesar, A.J. 2012. Occurrence of spot-form net blotch of barley in the Mon-Dak area of the US. American Phytopathological Society Annual Meeting. 102:S4.67.

Technical Abstract: Pyrenophora teres Drechs. causes net blotch of barley, a common foliar disease in cultivation zones around the world. Two forms, net form net blotch (NFNB) caused by P. teres f. teres and spot form net blotch (SFNB) caused by P. teres f. maculata are recognized. As in other parts of the Northern Great Plains including the Mon-Dak area (Western North Dakota and Eastern Montana), NFNB is prevalent. SFNB was first reported in Western Montana in 1983 and more recently in Eastern North Dakota in 2010 but not in the Mon-Dak area. Observation of unusual spot lesions on barley in fields at Williston ND, Nesson Valley ND and Sidney MT area in 2011 led to examination for occurrence of SFNB in the area. Diseased leaves from various barley cultivars showing spot symptoms were collected from the three locations. These were subjected to conidia examination and PCR using P. teres actin specific and ITS primers. Amplicons from the positive PCR results were purified and sequenced. Conidial morphology and sequence alignment with control P. teres f. teres and P. teres f. maculata cultures indicated the presence of SFNB incidence at all three locations. Pathogenicity tests were conducted by extracting conidia from diseased leaves from the three locations and inoculating barley plants. The infected plants were maintained in the greenhouse and observed for SFNB symptoms. Leaves showing spot-form lesions were harvested, examined by PCR and conidia characteristics as previously described. The results confirmed the observed incidence of SFNB. This is the first detection of SFNB in the Mon-Dak area.