Fungicide Effectiveness during the Various Developmental Stages of Peronophythora litchii In Vitro

Abstract

Litchi downy blight caused by Peronophythora litchii is one of the most destructive diseases suffered by litchi in China. This study has evaluated the activities of the fungicides dimethomorph (DMM), azoxystrobin (AZB), famoxadone (FMD), metalaxyl (MTL), cymoxanil (CYX) and mancozeb (MCB) on the mycelial growth, sporulation, zoospores release, and germination of sporangia as well as of cystospores of P. litchii. Dimethomorph and MTL inhibited mycelial growth more effectively than the other fungicides tested. Mycelial growth was affected less by MCB, and only weakly by AZB, FMD and CYX. Sporangia production was more strongly reduced by DMM and MTL than by AZB, FMD, CYX or MCB. Zoospore release from the sporangia was most sensitive to AZB and FMD, less sensitive to MCB and insensitive to DMM, MTL and CYX. Direct germination of sporangia of P. litchii was the most strongly inhibited by AZB and FMD, followed by DMM and MCB, whilst the sensitivity of this life stage to MTL and CYX was relatively low. Germination of encysted zoospores of P. litchii was the most sensitive to AZB and FMD, followed by DMM. Mancozeb was moderately active, while MTL and CYX did not inhibit this development stage. This is the first report on the in vitro response of the litchi pathogen, P. litchii, to fungicides. These findings can be valuable tools in setting up efficient disease management programmes to control litchi downy blight.

Control of litchi downy blight by zeamines produced by Dickeya zeae

“…Litchi downy blight is important postharvest disease caused by P. litchii , which leads to considerable losses during storage and transportation 17 18 . The disease is managed principally by application of synthetic fungicides such as mancozeb, cymoxanil, sulfur dioxide and benomyl 7 17 . To deal with the unavoidable emergence of fungicide tolerance and resistance problems, it is critical to discover and identify new antifungal molecules with different mechanisms for the control of this disease 6 7 19 .…”

“…The disease is managed principally by application of synthetic fungicides such as mancozeb, cymoxanil, sulfur dioxide and benomyl 7 17 . To deal with the unavoidable emergence of fungicide tolerance and resistance problems, it is critical to discover and identify new antifungal molecules with different mechanisms for the control of this disease 6 7 19 . In this study, we showed for the first time that ZMS, a new type of antibiotics produced by Dickeya zeae EC1, can effectively suppress the decay of post-harvest litchi fruits and peel browning caused by P. litchii .…”

“…P. litchii can grow on artificial media, which is unique as most downy mildews cannot be cultured under in vitro conditions 2 5 . In order to control the diseases of postharvest litchi fruits, a wide range of chemical fungicides have been tested and evaluated 7 . Given the unavoidable emergence of fungicide resistance as well as toxicological risks and environmental pollution concerns 8 , it is important to discover and develop alternative means to prevent and control postharvest litchi.…”

Generation and Characterization of Isolates of Peronophythora litchii Resistant to Carboxylic Acid Amide Fungicides

“…Peronophythora litchii is homothallic (self-fertile), and undergoes many short disease cycles per season with a high dispersal of spores over time and space and a random sexual recombination in the disease cycle (1). It could be classified as a medium-high risk pathogen (24).…”

“…Control of the disease is based on an integration of several cultural methods with the use of fungicides. In the 1990s, multisite inhibitors, such as mancozeb and chlorothalonil, and the target site-specific phenylamide metalaxyl were used to control this disease (24). A novel fungicide group, the carboxyl acid amide (CAA) fungicides, was first registered in 1996 in China for the control of litchi downy blight (25).…”