Exogenous Aspergillus aculeatus Enhances Drought and Heat Tolerance of Perennial Ryegrass

Abstract

Perennial ryegrass (<i>Lolium perenne</i>) is a cool-season grass whose growth and development are limited by drought and high temperature. <i>Aspergillus aculeatus</i> has been reported to promote plant growth and counteract the adverse effects of abiotic stresses. The objective of this study was to assess <i>A. aculeatus</i>-induced response mechanisms to drought and heat resistance in perennial ryegrass. We evaluated the physiological and biochemical markers of drought and heat stress based on the hormone homeostasis, photosynthesis, antioxidant enzymes activity, lipid peroxidation, and genes expression level. We found out that under drought and heat stress, <i>A. aculeatus</i>-inoculated leaves exhibited higher abscisic acid (ABA) and lower salicylic acid (SA) contents than non-inoculated regimes. In addition, under drought and heat stress, the fungus enhanced the photosynthetic performance, decreased the antioxidase activities, and mitigated membrane lipid peroxidation compared to non-inoculated regime. Furthermore, under drought stress, <i>A. aculeatus</i> induced a dramatic upregulation of <i>sHSP17.8</i> and <i>DREB1A</i> and a downregulation of <i>POD47</i>, <i>Cu/ZnSOD</i>, and <i>FeSOD</i> genes. In addition, under heat stress, <i>A. aculeatus</i>-inoculated plants exhibited a higher expression level of <i>HSP26.7a</i>, <i>sHSP17.8</i>, and <i>DREB1A</i> while a lower expression level of <i>POD47</i> and <i>FeSOD</i> than non-inoculated ones. Our results provide an evidence of the protective role of <i>A. aculeatus</i> in perennial ryegrass response to drought and heat stresses.