Formation of sclerotia in Sclerotinia ginseng and composition of the sclerotial exudate.

Dan Wang,Xinran Liu,Rujun Zhou,Junfan Fu,Zibo Li,Yueling Han,Yujiao Xie

doi:10.7717/peerj.6009

Abstract

BackgroundSclerotinia ginseng is a major devastating soil-borne pathogen of ginseng that can cause irreparable damage and large economic losses. This pathogen produces sclerotia, which are among the most persistent resting structures produced by filamentous fungi. The production of an exudate is a common feature of sclerotial development.MethodsS. ginseng was cultured on 10 different media and the following parameters were measured: mycelial growth rate (mm/day), initial formation time of exudate droplets, total quantity of exudate, number of sclerotia per dish, and sclerotial fresh/dry weight. The composition of the sclerotial exudate was analyzed using four methods (high performance liquid chromatography, gas chromatography-mass spectrometry, flame atomic absorption spectrometry, and Nessler’s reagent spectrophotometry).ResultsWe found that PDA was the optimal medium for exudate production, while SDA medium resulted in the highest mycelial growth rate. The earliest emergence of exudate droplets from sclerotia was on OA-YE and V8 media. The largest amount of sclerotia and the smallest sclerotia were produced on V8 medium. The maximum and minimum dry/fresh weight were obtained on MEA medium and V8 medium, respectively. The exudate contained organic acids (oxalic acid, gallic acid, ferulic acid, vanillic acid, caffeic acid, and tannic acid), carbohydrates (inositol, glucose, and trehalose), various ions (potassium, sodium, and magnesium), and ammonia.DiscussionThe functions of the identified compounds are discussed within the context of pathogenicity, sclerotial development, and antimicrobial activity. Our findings provide information about the production of sclerotia and the composition of sclerotial exudate that may be useful to develop strategies to control this disease.

Highlights

This strain was cultivated on 10 different media, as follows: potato dextrose agar (PDA), oatmeal agar (OA), oatmeal-yeast extract agar (OA-YE), 5% malt extract agar (MEA), malt extract-peptone-dextrose agar (MEApeptone), carrot decoction agar (CA), Sabouraud’s agar (SDA), Richard’s medium agar, V8 juice agar (V8), and Czapek-Dox solution agar (Czapek) at optimal temperature (20 ± 1 ◦C) in the dark in Petri dishes
The fastest mycelial growth rate of isolate GSgF-01 was on SDA medium (13.47 ± 0.93 mm d−1), followed by PDA medium (10.81 ± 1.68 mm d−1), and the slowest growth rate was on Czapek medium (4.48 ± 1.73 mm d−1) (Table 1)
We evaluated the mycelial growth rate, total quantity of exudate, number of sclerotia, sclerotial fresh weight and dry weight, and sclerotial distribution of S. ginseng grown on 10 different media

Summary

Introduction

Sclerotinia ginseng is a major devastating soil-borne pathogen of ginseng that can cause irreparable damage and large economic losses. This pathogen produces sclerotia, which are among the most persistent resting structures produced by filamentous fungi. The production of an exudate is a common feature of sclerotial development. S. ginseng was cultured on 10 different media and the following parameters were measured: mycelial growth rate (mm/day), initial formation time of exudate droplets, total quantity of exudate, number of sclerotia per dish, and sclerotial fresh/dry weight. Our findings provide information about the production of sclerotia and the composition of sclerotial exudate that may be useful to develop strategies to control this disease

Methods

Results

Discussion

Conclusion