ARS | Publication request: Molecular identification and pathogenic behavior of Albugo sp., a potential bioherbicide of perennial pepperweed in northern Nevada

Submitted to: International Symposium on Biological Control of Weeds
Publication Type: Abstract Only
Publication Acceptance Date: May 4, 2011
Publication Date: September 14, 2011
Citation: Wang, S., Rector, B.G. 2011. Molecular identification and pathogenic behavior of Albugo sp., a potential bioherbicide of perennial pepperweed in northern Nevada. International Symposium on Biological Control of Weeds. 13:3.

Technical Abstract: Perennial pepperweed (PPW, Lepidium latifolium) is a cruciferous plant native to Eurasia that is a noxious weed in the western USA. In northern Nevada, PPW plants in the field are commonly infected with white rust fungus (Albugo sp.), exhibiting white pustules on the leaves and stems of mature plants in summer. Molecular taxonomic identification of the Albugo species encountered on PPW in Nevada and preliminary host-specificity tests were performed to assess the potential of this fungus as a bioherbicide for control of PPW. Using genus-specific PCR primers (DC6 and LR-0), a region of rDNA including sections of ITS1, 5.8S ribosomal RNA gene, and ITS2 were amplified, subcloned into the pGEM®-T vector, and sequenced using the T-7 promoter and SP6 upstream primers. A BLAST search matched DNA sequences of the Nevada isolate of Albugo sp. with five voucher isolates of Albugo candida (98% identity, E value=0.0) as well as three isolates of Albugo lepidii (99% identify, E value=0.0). Thus, this Nevada isolate has significant variations within its rDNA sequence from that of both A. candida and A. lepidii and its identity remains somewhat ambiguous. Preliminary host-range tests under both greenhouse and growth chamber conditions have shown that the Nevada isolate infected PPW but there were no symptoms on any of 12 varieties of cruciferous vegetables during tests of up to one month. These preliminary results suggest that the Nevada Albugo isolate may represent a previously unknown pathotype with high host-specificity on PPW. Further studies on the host-specificity and pathogenicity of Nevada white rust isolates, particularly for early-season application to new PPW growth, will be necessary to better understand the potential benefits and risks of using this fungus as a bioherbicide against PPW in Nevada.