Antifungal Effects of Rhizospheric Bacillus Species Against Bayberry Twig Blight Pathogen Pestalotiopsis versicolor

Md Arshad Ali,Xingjiang Qi,Jinyan Luo,Haiying Ren,Bin Li,Temoor Ahmed,Qianli An

doi:10.3390/agronomy10111811

Abstract

Bayberry is an attractive, nutritious, and popular fruit in China. The plant fungal pathogen Pestalotiopsis versicolor XJ27 is the causative agent of bayberry twig blight disease, which severely affects bayberry production. Traditional control techniques, such as chemical fungicides, are being used to control this disease; however, these techniques cause environmental and health hazards. In this study, we screened sweet potato rhizospheric bacteria with biocontrol potentials against P. versicolor XJ27, the bayberry twig blight pathogen. Ten isolates showed inhibition; Bacillus siamensis S3 and Bacillus tequilensis S5 showed the highest fungal growth inhibition. The antagonistic bacterial culture suspensions of S3 and S5 inhibited the mycelial growth by 82.9% and 76.2%, respectively. Their extracellular culture filtrates had mycelial growth inhibition of 86.8% and 82.2%, respectively. In detached leaf assay, the extracellular culture filtrates of S3 and S5 inhibited the size of the leaf lesion by 82.3% and 76.2%, respectively. SEM and TEM imaging showed a severe hyphal-damaged structure caused by the antagonistic bacteria. The fungal inhibition mechanisms might employ the hydrolytic enzymes and lipopeptides produced by the bacteria. Both the S3 and S5 have chitinase and protease activity; they produce a series of lipopeptides such as surfactin, iturin, and mycosubtilin. Therefore, we can suggest these bacteria as biocontrol agents for bayberry twig blight disease as an alternative to fungicides based upon their attributes of antifungal activity.

Highlights

Bayberry (Myrica rubra) is a fruit plant in tropical and subtropical zones; its origin is easternAsia [1,2]
We can suggest these bacteria as biocontrol agents for bayberry twig blight disease as an alternative to fungicides based upon their attributes of antifungal activity
Ten-fold serial dilutions were prepared from soil suspension, and 100 μL of diluted samples were poured on nutrient agar (NA; beef extract 3 g, glucose 2.5 g, NaCl 5 g, tryptone 10 g, and agar 15 g per liter, pH 7.4 ± 0.2) and tryptic soy agar (TSA; tryptone 15 g, soy peptone 5 g, NaCl 5 g, and agar 15 g per liter, pH 7.3 ± 0.2) media

Summary

Introduction

Bayberry (Myrica rubra) is a fruit plant in tropical and subtropical zones; its origin is easternAsia [1,2]. Bayberry is known as “precious southern Yangtze fruit of early summer” for its attractive color and flavor [1,3]. It can be eaten as fresh fruit or some delicious food products like jelly, jam, juice, wine, and other pastries can be prepared from bayberry for consumption. In China, this is a popular southern Yangtze fruit during summer, as well as a good source of natural antioxidants. This fruit has drawn attention for containing a high amount of flavonoids, which is Agronomy 2020, 10, 1811; doi:10.3390/agronomy10111811 www.mdpi.com/journal/agronomy

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