No abstract

Agricultural productivity and sustainability are continually challenged by emerging and indigenous pathogens. Currently, many pathogens can be combated only with biocides or environmentally dangerous fumigants. Here, we report a rapid and pathogenspecific strategy to reduce infection by organisms that target plant roots. Combinatorially selected defense peptides, previously shown to effect premature encystment of Phytophthora capsici zoospores, were fused to maize cytokinin oxidase͞dehydrogenase as a display scaffold. When expressed in tomato roots, the peptidescaffold constructs were secreted and accumulated to sufficient concentrations in the rhizosphere to induce zoospore encystment and thereby deter taxis to the root surface. Pathogen infection was significantly inhibited in roots expressing bioactive peptides fused to the maize cytokinin oxidase͞dehydrogenase scaffold. This peptide-delivery technology is broadly applicable for rapid development of plant defense attributes against plant pathogens.disease resistance ͉ Phytophthora

Phakopsora pachyrhizi, the fungal pathogen that causes Asian soybean rust, has the potential to cause significant losses in soybean yield in many production regions of the United States. Germplasm with durable, single-gene resistance is lacking, and control of rust depends on timely application of fungicides. To assist the development of new modes of soybean resistance, we identified peptides from combinatorial phage-display peptide libraries that inhibit germ tube growth from urediniospores of P. pachyrhizi. Two peptides, Sp2 and Sp39, were identified that inhibit germ tube development when displayed as fusions with the coat protein of M13 phage or as fusions with maize cytokinin oxidase/dehydrogenase (ZmCKX1). In either display format, the inhibitory effect of the peptides on germ tube growth was concentration dependent. In addition, when peptides Sp2 or Sp39 in either format were mixed with urediniospores and inoculated to soybean leaves with an 8-h wetness period, rust lesion development was reduced. Peptides Sp2 and Sp39, displayed on ZmCKX1, were found to interact with a 20-kDa protein derived from germinated urediniospores. Incorporating peptides that inhibit pathogen development and pathogenesis into breeding programs may contribute to the development of soybean cultivars with improved, durable rust tolerance.

Isolating DNA from microbes on the surface of a grape berry is a challenge due to their adhesion to the thick berry skin and cuticle, making studies of the grape microbiome challenging. We developed a field-to-lab DNA extraction procedure that starts in the vineyard, disrupts the grape berry surface while en route to the lab through agitation, and efficiently extracts microbial DNA from the surface of the grape. It is cost effective and utilizes commonly available laboratory chemicals with low toxicity (Table 1). This protocol allows researchers to extract DNA from the grape berry surface in the field, therefore undergoing minimal manipulation of those microbiomes before DNA extraction.