Regalia® Bioprotectant in Plant Disease Management
Plants have long been used as herbal medicines for treatment of human diseases. However, only a limited number of plant extracts have been developed into fungicides for plant disease control. The commercialization of Regalia illustrates the potential for plant extracts to be an important tool for disease management in both organic and conventional production systems and emphasises the need for additional plant extracts to be explored as a source of biopesticides. Regalia is formulated from the extract of giant knotweed (Reynoutria sachalinensis (REYSA)) and is now becoming widely used in commercial crop production. Giant knotweed is used as a food in many countries, especially Asia. Knotweed was formerly formulated as Milsana in the1980s and was tested in field trials through the 1990s. Trial demonstrations were limited to cucumber powdery mildew (Sphaerotheca fuliginea) and a few other diseases such as Botrytis fruit rot (Botrytis cinerea) and wheat powdery mildew (Blumeria graminis f. sp. tritici). Since the 2009 introduction as the reformulated product Regalia by Marrone Bio Innovations, extensive tests have been conducted in the laboratory, glasshouse and field on multiple crop-disease systems to evaluate its efficacy for disease control. Test results demonstrate the efficacy of Regalia? applied as a foliar spray in controlling a wide range of fungal and bacterial diseases, such as powdery mildew of cucurbits, downy mildew of lettuce (Bremia lactucae), Botrytis of grapes and strawberries, bacterial spot of tomatoes and peppers (Xanthomonas campestris pv. vesicatoria), Cercospora on soybeans (Cercospora kikuchii) and bacterial canker on citrus (Xanthomonas axonopodis pv. citri), amongst others. The broad spectrum of disease control by Regalia relies on the unique mechanism of induced plant resistance. Studies in plants show that Regalia? treatment increases the activity of chalcone synthase and chalcone isomerase in the phenylpropanoid pathway and induces the production and accumulation of phytoalexins. Simple phenolic compounds, which are fungitoxic, also accumulate. Additional studies show that Regalia increases the papillae formation at pathogen penetration sites as well as the liginification of plant cell walls. Activities of pathogenesis-related protein (PR-proteins) such as chitinase, glucanase, and peroxidase are also increased. Regalia is an excellent tool for fungicide resistance management and is synergistic with commonly used fungicides, such as azoles, strobilurins, and sulfur in controlling powdery mildew and leaf spot diseases, copper in controlling bacterial diseases, and mancozeb and mefenoxam in controlling downy mildew. To enhance soil-borne disease control and increase emergence, multiple delivery methods can be used, such as seed treatment, soil drenches, irrigation applications, and dipping seedlings prior to transplanting. The successful commercialization of Regalia is the result of extensive research into efficacy and formulations, demonstration of all application options for efficacy, and innovative marketing strategies. Integration of plant extracts in disease management programs can increase yields and quality, reduce fungicide resistance in pathogens, lower residue of synthetic fungicides in plants and soil, and protect human health and the environment.
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Document Type: Research Article
Publication date: February 1, 2012
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