Preliminary Investigation of Effect of Neem-Derived Pesticides on Plasmopara halstedii Pathotype 704 in Sunflower under In Vitro and In Vivo Conditions.

Pratik Doshi,Rita Bán,Ahmed Ibrahim Alrashid Yousif,György Turóczi,Nisha Nisha,Katalin Körösi

doi:10.3390/plants9040535

Abstract

Two neem-derived pesticides were examined under in vitro and in vivo conditions to test their efficacy in controlling Plasmopara halstedii pathotype 704, a causal agent of downy mildew in sunflower. All the tested concentrations of neem leaf extract and the highest concentration of commercial neem product significantly reduced the sporangial germination under in vitro conditions. In in vivo experiment, 3-days old pre-treated seedlings with both concentrations of neem leaf extract and the highest concentration of commercial product showed a significant reduction in the infection indicating possible systemic effect of neem. When the seedlings were treated following the infection with P. halstedii (i.e., post-treatment), only the highest concentrations of neem leaf extract and the commercial product showed a significant reduction in the infection indicating curative effect of neem. Possibilities for the control of P. halstedii with neem-derived pesticides are discussed.

Highlights

Sunflower Helianthus annuus L. is one of the most important oilseed crops in the world
In the pre-treatment experiment, we found in our study that both the selected concentrations of neem leaf extract and highest concentration of NeemAzal T/S successfully reduced the infection in sunflower
Our results contradict the findings of Rovesti et al [23], where neem extract was found to be ineffective against P. infestans, but they are in line with the results found by Ngadze [22]

Summary

Introduction

Sunflower Helianthus annuus L. is one of the most important oilseed crops in the world. This pathogen affects sunflower yield losses, more than 85%, as well as the cost of sunflower crop protection and resistance breeding [1,2,3]. The distribution and genetic variability of P. halstedii have been studied extensively, especially in North. This disease is mostly initiated by the soil-borne oospores and occasionally from infected seeds. Plasmopara halstedii infection in the sunflower usually takes place in the below ground plant parts by direct penetration in the roots [7]. Seedling damping-off occurs by root infection, whereas severe symptoms, such as stunted plants (dwarfing), chlorosis of leaves, and white sporulation to the production of infertile flowers, resulting in yield loss [9,10]

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