Abstract
Calotropis procera (Aiton) Dryand (commonly known as the apple of sodom, calotrope, and giant milkweed) is an evergreen, perennial shrub of the Apocynaceae family, and is mainly found in arid and semi-arid regions. Previous studies have established the toxic effects of Calotropis procera (C. procera) (Aiton). Its extract is used as one of the vital alternatives to pesticides due to its effective impacts on several pathogens and to combat insect pests that cause severe damage to several crops, but so far, its effects on combating Fusarium oxysporum f. sp. lycopersici (FOL) have not yet been evaluated. Therefore, the current study focuses on evaluating the effects of the aqueous extract of this plant on FOL by studying physicochemical indicators. In Saudi Arabia and many other countries, such disease is considered as one of the critical factors affecting tomato growth and production. For the control of Fusarium wilt disease (Fwd), many strategies have been developed, but are limited in their use. Ten isolates of the pathogens were obtained from diseased tomato plants. These isolates were able to exhibit symptoms of tomato wilt, and they varied in their virulence. Isolate No. 5 caused the highest severity of the disease (73%). According to these results, we used this isolate in the following experiment, which was identified by ITS sequences as F. oxysporum f. sp. lycopersici. Following intensive screening studies, we selected aqueous plant extract of C. procera to study its effectiveness against Fwd of tomato plants and their antifungal activity or induce systemic resistance in plants. All concentrations of C. procera extracts suppressed growth of the pathogen. The highest reduction of mycelia growth was obtained by aqueous extract at 15%, it reduced the pathogen growth to 70.2%, relative to the control. In greenhouse conditions, the aqueous C. procera extract at 5, 10, and 15% significantly reduced Fwd of the tomato compared to the infected control (52.01, 69.86, and 83.6%, respectively). The use of aqueous C. procera extract at 5, 10, and 15% significantly enhanced the fresh and dry weight of tomato plants (g plant−1) compared to inoculated plants (for fresh weight: 50, 66.6, and 86.6 and for dry weight: 60, 100, and 120%, respectively). Total phenols and flavonoids as well as antioxidant enzymes were increased in inoculated or non-inoculated tomato plants after being treated with aqueous extracts of C. procera.
Highlights
It was found that all these isolates showed typical symptoms of tomato wilt, but varied in their virulence
This study focused on wilt disease, which causes reduced production of tomato plants in all countries that grow them, and it is known that the cause of this disease is the fungus Fusarium oxysporium f. s. lycopersici
Ten isolates were isolated from tomato plants in Jeddah city; all these isolates were able to cause wilt disease on tomato plants to various different degrees, and these results are in agreement with these obtained by Abo-Elyousr and Mohamed [2] who determined that fungal isolates differ in their ability to cause disease
Summary
Tomatoes (Lycopersicum esculentum, Mill) are one of the most profitable and popular vegetables grown worldwide, are ranked second after potatoes among vegetable plants, and the first among processed crops in terms of the areas planted and the production with vegetables, globally. The tomato plant faces major challenges in terms of its growth and productivity, the most important of which is its infection with many plant distributed under the terms and conditions of the Creative Commons. Horticulturae 2022, 8, 197 pathogens, such as fungi, bacteria, viruses, nematodes, and biotic factors [1]. Root rots, damping-off, and wilt are among the important fungal diseases. Fusarium oxysporum is a well-known plant pathogen that causes significant harm to a variety of host plants [2]. Tomato wilt disease causes reduction in weight of tomato fruits and productivity [3,4]
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