Phylloplanins Reduce the Severity of Gray Leaf Spot and Brown Patch Diseases on Turfgrasses

Plant-produced, natural-product fungicides should be evaluated for their potential to complement or replace synthetic fungicides that are major components in the management of high maintenance turf. Tobacco (Nicotiana tabacum L.) cultivar T.I. 1068 and sunflower (Helianthus annuus L.) phylloplanins (T- and S-phylloplanins), collected in leaf-water washes (LWWs) of plants, and recombinant T-phylloplanin inhibit Peronospora tabacina D.B. Adam (oomycete) spore germination and reduce blue mold disease on tobacco. Here, in vitro (hyphal extension) and in vivo studies were conducted to test the ability of T- and S-phylloplanins to inhibit growth of the turf pathogens Pyricularia oryzae Cavara (ascomycete) and Rhizoctonia solani J.G. Kühn (basidiomycete) and to test protection of turfgrass plants from gray leaf spot and brown patch diseases. Hyphal extension assays showed that LWWs containing T- and S-phylloplanins inhibited both pathogens. Spraying potted grass plants with LWWs containing T- and S-phylloplanins followed by inoculation with pathogens resulted in 97 and 88% inhibition of P. oryzae disease and 94 and 82% inhibition of R. solani on annual (Lolium multiflorum Lam. cv. Linn) and perennial (Lolium perenne L. cv. Double Eagle Blend) ryegrasses, respectively, under the conditions tested. In addition, T- and S-phylloplanins led to 94 and 100% symptom reduction, respectively, on creeping bentgrass (Agrostis stolonifera L. cv. L-93), for R. solani only. Results indicate that T- and S-phylloplanins have broad selectivity, inhibiting at least one member of the ascomycete and basidiomycete phyla, and may be useful as exogenously applied or endogenously expressed natural-product antifungal agents to protect turf, crops, and other plants.