Novel Insights into the Effect of Pythium Strains on Rapeseed Metabolism

Abstract

<i>Pythium oligandrum</i> is a unique biological control agent. This soil oomycete not only acts as a mycoparasite, but also interacts with plant roots and stimulates plant defense response via specific elicitors. In addition, <i>P. oligandrum</i> can synthetize auxin precursors and stimulate plant growth. We analyzed the secretomes and biochemical properties of eleven <i>Pythium</i> isolates to find a novel and effective strain with advantageous features for plants. Our results showed that even closely related <i>P. oligandrum</i> isolates significantly differ in the content of compounds secreted into the medium, and that all strains secrete proteins, amino acids, tryptamine, phenolics, and hydrolytic enzymes capable of degrading cell walls (endo-β-1,3-glucanase, chitinase, and cellulase), exoglycosidases (especially β-glucosidase), proteases, and phosphatases. The most different strain was identified as a not yet described <i>Pythium</i> species. The changes in metabolism of <i>Brassica napus</i> plants grown from seeds coated with the tested <i>Pythium</i> spp. were characterized. Enhanced levels of jasmonates, ethylene precursor, and salicylic acid may indicate better resistance to a wide variety of pathogens. Glucosinolates, as defense compounds against insects and herbivores, were enhanced in young plants. Altogether, <i>P. oligandrum</i> strains varied in their life strategies, and either they could perform equally as plant growth promoters and mycoparasites or they had developed one of these strategies better.