Abstract
Eggplant (Solanum melongena L.) production has gone through increasing difficulties due to relatively low yields in the last few years in Iraq. Alternaria solani, the causal agent of eggplant early blight; attacks hybrid and local varieties either in open field or in the greenhouse, causing a serious damage that led to decrease in crop yield. The strategies employed to manage this disease by Iraqi farmers were the synthetic fungicides application. In this study, several assays were conducted such as poisoned food technique (in vitro assay) and greenhouse experiment (in vivo assay); to evaluate the inhibitory efficacy of 3 three synthetic fungicides including; Topas® 100 (penconazole), Tilt 250 (propiconazole) and Leimay® (amisulbrom) on A. solani mycelial growth and disease intensity. In laboratory assays, Topas® 100 and Tilt 250 exhibited high inhibitory activities against A. solani as an airborne pathogen; recording mycelial inhibition rate above 94 % at a concentration of 1000 mg l. Furthermore, these two fungicides when applied preventively in greenhouse assays reduced significantly the disease severity index (DSI) by 18.83 % and 26.16 %, respectively. Current results revealed that Topas® 100 and Tilt 250 caused the highest antifungal potential manifested through reduction rate of fresh weight (9.62 and 8.58 g, respectively), and dry weight (4.61 and 4.60 g, respectively). Moreover, both fungicides recorded the highest peroxidase activities of 4.128 units/g/ml/min. and 3.038 units/g/ml/min., respectively. Current findings can be used to assist the eggplant growers to improve the control of early blight disease, and increase the marketable yields of this crop.
Highlights
Blight caused by Alternaria solani is a common and widespread foliar disease of eggplant (Salih and Abdul Ridha, 2019)
Alternaria solani used in the present research was obtained from the Laboratory of Plant Protection, College of Agriculture, Basra, Iraq; isolated from eggplant leaves collected from an experimental greenhouse in Basra, Iraq, during the period of January- March, 2020
This study showed that Topas® 100 and Tilt 250 systemic fungicides have significant inhibitory effects on radial growth of A. solani in Potato dextrose agar (PDA) plates
Summary
Blight caused by Alternaria solani is a common and widespread foliar disease of eggplant (Salih and Abdul Ridha, 2019). The increasing importance of A. solani has led to several studies about the best way to control this disease (Iram et al, 2018; Chohan et al, 2019; Shafique et al, 2021). For cultivars susceptible to early blight, responses to fungicide treatment can be highly important and cause increases in crop yield above 127 % (Teng and Bissonnette, 1985; ElDebaiky, 2018). The most common way to prevent pathogens resistance to fungicides involve reducing the application numbers of the fungicides ‘at-risk’ per growing season; through applying them alternately and using fungicides with different modes of action (Rosenzweig et al, 2008b; Horsfield et al, 2010). The objective of this study was to determine the inhibitory efficacy of the tested fungicides on the causal fungus and\or on the disease severity index (DSI); under laboratory and greenhouse conditions
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