Can a fungal volatile organic compound mitigate abiotic and biotic stress impacts in perennial ryegrass grown for seed production?

Abstract

Trichoderma fungi produce the volatile organic compound 6-pentyl-alpha-pyrone (6-PP) which can prime plant defences against abiotic and biotic stress. Coating seeds with 6-PP is one delivery option, and this method was used to assess the ability of 6-PP to mitigate abiotic (heat) and biotic (Rhizoctonia solani Kuhn) stress in perennial ryegrass (Lolium perenne L.). For seeds of cv. Base coated with 6-PP at rates of 75 and 114 mM germination was 90% which did not differ from the untreated control, but germination for the 228 and 350 mM rates was 81% and 85%. 6-PP seed coating did not affect the seed to seedling transmission of six Epichloë endophytes but for two of the six seed to seed transmission was reduced by around 20%. 6-PP seed coating (75 and 114 mM) was then assessed as a primary strategy against the soil-borne pathogen R. solani in a glasshouse experiment. 6-PP significantly increased seedling emergence and reduced the disease impact caused by the pathogen, with the higher rate increasing root length by 77% and root volume by 131% over that of the pathogen control. 6-PP seed coating (75 mM) was finally used to assess the ability of the seed crop of cv. Base produced to withstand heat stress (180℃h) at flowering or during seed development (70% seed moisture content). Plants grown from 6-PP coated seed had a 25% greater seed yield and 15% higher thousand seed weight than the control when the heat stress was applied at flowering, and the seeds produced had a germination of 82% cf. 45% for the control. When heat stress was applied during seed development the germination of seeds produced from the plants grown from 6-PP coated seed was 78% and that of the control was 48%. 6-PP applied as a seed coating enhanced stress resilience in perennial ryegrass and may offer a strategy for mitigating the negative impacts of climate change on seed yield and quality