Eco-friendly rhamnolipid based fungicides for protection of soybeans from Phytophthora sojae

BACKGROUND Excessive use of chemical fungicides over the years for plant pathogen control has caused unwanted damage to non-target organisms and resistance buildup in the target organisms. These harmful effects have prompted the industry to look for more sustainable and eco-friendly solutions. Rhamnolipid is a naturally occurring surfactant that is biodegradable, relatively innocuous to non-target species and can effectively lyse zoospores, the life form responsible for the spread of Phytophthora. In this study, rhamnolipid based coatings were developed and evaluated for protection of soybeans from P. sojae zoospores. RESULTS Pure (acidic) rhamnolipid, when coated on the soybeans, affects the germination negatively. However, sodium and calcium complexed rhamnolipids do not interfere with germination. Seeds coated with 15-20 mg of developed formulation were planted in soil pots and then subjected to P. sojae infection by simulating flooding conditions and zoospore inoculation. Statistical analysis showed that sodium rhamnolipid based coating significantly improved the germination in presence of P. sojae from 42% to 73% (P = 0.017) while the germination of stress-free control was 85% (statistically similar to coated seeds, P = 1). CONCLUSION Neutralized rhamnolipid can protect soybeans from P. sojae without any negative effect on germination. This work illustrates the strategy to use rhamnolipid as effective fungicide. (c) 2019 Society of Chemical Industry