Arbnora Berisha, Katalin Körösi, Rita Bán

Efficacy of BTH and NeemAzal against an aggressive isolate of sunflower downy mildew caused by Plasmopara halstedii

Introduction

Efficacy of bth and neemazal against an aggressive isolate of sunflower downy mildew caused by plasmopara halstedii. Evaluate BTH and NeemAzal's efficacy as resistance inducers against aggressive sunflower downy mildew caused by Plasmopara halstedii, offering eco-friendly disease control.

Abstract

Sunflower is an important oilseed crop, but its yield is highly affected by devastating diseases such as sunflower downy mildew caused by Plasmopara halstedii. The high variability of this pathogen compromises the effective management of sunflowers; therefore, IPM including alternative methods is a promising tool against downy mildew. The goal of our study was to assess the effectiveness of BTH (benzothiadiazole in Bion 50 WG) and NeemAzal as inducers of resistance against sunflower downy mildew. Sunflower seedlings were treated with BTH and NeemAzal before inoculation with varying concentrations of Plasmopara halstedii sporangia and incubated overnight at 16°C. Disease severity was assessed using a 0-4 scale, and plant height was measured twice. Histological analysis of sunflower hypocotyls was conducted to examine pathogen structures and host reactions. Both BTH and NeemAzal treatments reduced disease development, with BTH showing greater efficacy in inhibiting pathogen growth and reducing plant height compared to NeemAzal. Histological examination revealed decreased presence of pathogen structures and increased necrosis in treated plants. Further experiments with inducers are recommended. Preliminary results indicate that NeemAzal and BTH reduce the progression of disease symptoms. Plant inducers offer an eco-friendly approach to disease management, including the control of sunflower downy mildew.

Review

This study addresses a critical challenge in agriculture: the effective management of sunflower downy mildew, caused by the highly variable pathogen *Plasmopara halstedii*. The authors rightly emphasize the necessity of Integrated Pest Management (IPM) strategies, particularly those incorporating alternative and eco-friendly methods. By focusing on BTH (benzothiadiazole) and NeemAzal as potential resistance inducers, the research aligns with contemporary efforts to reduce reliance on conventional fungicides and provides a timely contribution to sustainable disease management practices. The clear objective of assessing the efficacy of these compounds is well-defined and relevant to both scientific understanding and practical application. The methodology employed involved treating sunflower seedlings with BTH and NeemAzal prior to inoculation with varying concentrations of *P. halstedii* sporangia, followed by overnight incubation. Disease severity was quantitatively assessed using a 0-4 scale, alongside measurements of plant height, offering both macroscopic and growth-related indicators of disease progression. A significant strength of the study lies in its integration of histological analysis of hypocotyls, which provided valuable microscopic evidence of host reactions and pathogen structures. The findings consistently demonstrated that both BTH and NeemAzal reduced disease development, with BTH exhibiting superior efficacy in inhibiting pathogen growth and ameliorating plant height reduction. Histological observations corroborated these results by revealing a decreased presence of pathogen structures and increased necrosis in treated plants, substantiating the induction of host defense mechanisms. While the preliminary results are promising and underscore the potential of plant inducers as an eco-friendly approach, the abstract suggests areas for further investigation. The recommendation for "further experiments with inducers" implies that the current study provides foundational data. Future research could delve deeper into the specific biochemical and molecular pathways induced by BTH and NeemAzal, quantifying resistance gene expression or defense metabolite production. Additionally, evaluating these inducers under varied environmental conditions, with different sunflower genotypes, and, crucially, in field trials, would be essential to translate these laboratory findings into practical agricultural solutions. This work represents a valuable initial step towards developing sustainable and effective strategies for controlling sunflower downy mildew.

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