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Yield losses of crops due to plant pathogens are a major threat in all agricultural systems. In view of environmental issues and legislative limitations for chemical crop protection products, the need to design new environmentally friendly disease management strategies has gained interest. Despite the unique capability of green leaf volatiles (GLVs) to suppress a broad spectrum of plant pathogens, their capacity to control the potato late-blight-causing agent Phytophthora infestans has not been well studied. This study addresses the potential role of the GLV Z-3-hexenyl acetate (Z-3- HAC) in decreasing the severity of late blight and the underlying gene-based evidence leading to this effect. Nine-week-old potato plants (Solanum tuberosum L.) were exposed to Z-3-HAC before they were inoculated with P. infestans genotypes at different time points. These pre-exposed potato plants exhibited slower disease development after infection with the highly pathogenic genotype of P. infestans (EU-13-A2) over time. Qualitative assessment showed that the exposed, infected plants possessed significantly lower sporulation intensity and disease severity compared to the control plants. Hypersensitive response (HR)-like symptoms were observed on the treated leaves when inoculated with different pathogen genotypes. No HR-like lesions were detected on the untreated leaves after infection. It was shown that the transcript levels of several defense-related genes, especially those that are involved in reactive oxygen species (ROS) production pathways were significantly expressed in plants at 48 and 72 h postexposure to the Z-3-HAC. The current work provides evidence on the role of Z-3-HAC in the increased protection of potato plants against late blight through plant immunity and offers new opportunities for the sustainable control of potato diseases. [ABSTRACT FROM AUTHOR]

Late blight caused by the oomycete Phytophthora infestans is considered the biggest threat to potato farming worldwide. For susceptible cultivars, the disease is often managed by frequent applications of fungicides to reduce yield loss. The use of bio-based compounds that interfere with biologically active systems is an innovative strategy for improving disease management. In the present work, the control of P. infestans infection on potatoes by potassium phosphite (KPhi) combined with recommended and reduced doses of active ingredients (Ais) from different fungicides was evaluated. The protective effects of different combinations were initially assessed in vivo and subsequently compared with a greenhouse screening. The active ingredients cyazofamid (CFD) and mancozeb (MCB), used at recommended and reduced doses, were less effective at reducing P. infestans infections than when combined with KPhi. In greenhouse trials, CFD, mandipropamid (MPD) and MCB at recommended doses were the most effective treatments when combined with KPhi; meanwhile, the combination of KPhi with azoxystrobin (AZ), benthiavalicarb-isopropyl/mancozeb (ISO/MCB), and CFD at reduced doses exhibited strong protective activity compared to other similar combinations. This decreased the severity of infection by P. infestans up to ~89%. Greenhouse experiments also demonstrated that a combination of KPhi and CFD at both doses caused the highest reduction in disease severity (up to ~90%) within 35 days of infection. In microplot experiments, KPhi delayed the progression of late blight in susceptible potato varieties; therefore, in the combined treatments AUDPC values were significantly lower than those obtained after applications with CFD doses, providing sufficient protection against late blight. Our data suggest that optimizing the formulation with addition of KPhi could result in a lower recommended dose. This would result in a reduction of the active compounds of the fungicides in potato farming. Furthermore, the impact of KPhi on late blight development makes it a potential component for incorporation into an integrated pest management system. [ABSTRACT FROM AUTHOR]

The current study aimed to evaluate the potential biocontrol capabilities of different essential oils (EOs) including juniper, tea tree, clove, thyme, cinnamon, turmeric, pepper and rosemary at application rates of 0.41, 0.83, 1.66, 3.33 and 6.66 μL mL−1 for control of Phytophthora infestans ; the causal agent of potato late blight in vivo and under greenhouse conditions. In particular we tested the highly pathogenic genotype, EU-13-A2. Plant extract Timbor® (Thymus vulgaris -derived compound) was similarly applied as an alternative reference to the essential oils. The effectiveness of plant compounds was initially determined by measuring the effective dose (ED 50) reducing P. infestans sporangial germination by 50%. Among the nine tested compounds, thyme and tea tree EOs showed the strongest inhibitory effect on sporangial germination, with ED 50 values between 0.12 and 0.37 μL mL−1, compared to the fungicide control Ranman-top® (160 g L−1 Cyazofamide). Clove EO, thyme EO and Timbor® significantly inhibited P. infestans mycelial growth even at the lowest concentration tested (0.41 μL mL−1). Inhibitory effects of compounds were also assessed in response to late blight in vivo , and the results were then compared with greenhouse screening. In the detached-leaflet assay, pepper, rosemary EOs and Timbor® showed reduction of disease development at all concentrations except for 0.41 μL mL−1. In dose–responses, rosemary, thyme EO and Timbor® were the most effective compounds in reducing late blight (more than 80% disease reduction) over time. Within a 35-day period, these compounds also resulted in the lowest level of disease severity in susceptible potato plants (cv. Bintje) when treated 12 h before inoculation, demonstrating their protective effect against late blight under greenhouse conditions. This study presents evidence for the potential use of commercial plant derived compounds as botanical fungicides against P. infestans to control infection on potato plants. • First study on anti-oomycidal activity of juniper, tea tree, pepper, clove and turmeric EOs against Phytophthora infestans. • Considering rosemary, thyme, turmeric, tee tree EOs and Timbor® as effective compounds in reducing potato late blight. • High conformity of detached-leaflet assay with whole-plant assay in dose-responses for Phytophthora blight assessments. • Providing a baseline information on application of essential oils as botanical fungicide against late blight in the field. [ABSTRACT FROM AUTHOR]

A collection of by-products was surveyed for novel biostimulant and biopesticide activity by establishing a screening platform (Bio2Bio) that integrated a broad spectrum of in vitro and in planta bioassays. Here, we report plant growth-promoting and biopesticide activities obtained from four solvent extracts of maize distillers' dried grains with solubles (DDGS), a bioethanol fermentation by-product. The hexane extract stimulated Arabidopsis primary root growth, whereas the ethanol extract enhanced tomato shoot growth and fresh biomass. The water extract showed fungicide, acaricide, nematicide, and protective activities, specifically conferring disease tolerance by inducing the plant immune response. We demonstrate significant biopesticide effects of DDGS water extract against the fungus Magnaporthe oryzae (32 % in vitro efficacy), oomycete Phytophthora infestans (73 % in planta efficacy), and spider mite Tetranychus urticae (60 % in vitro efficacy), as well as plant-induced resistance against the fungal pathogen Botrytis cinerea (30 % in planta efficacy) and root-knot nematode Meloidogyne graminicola (91 % in vitro and 50 % in planta efficacy). The broad range of bioactivities suggests that DDGS is a complex mixture composed of a wide variety of plant metabolites. DDGS represents a valuable source for discovering bioactive ingredients with potential use as biostimulants and/or biopesticides. [Display omitted] • A biostimulant and biopesticide screening platform was in-house built. • The platform comprised a series of in vitro and in planta bioassays. • DDGS, a bioethanol by-product, contains a wide spectrum of bioactive compounds. • Organic solvent extract derived from DDGS showed promising biostimulant activity. • DDGS water extract exerted significant biopesticide and bioprotectant effects. [ABSTRACT FROM AUTHOR]