Abstract
Fungal diseases of plants continue to contribute to heavy crop losses in spite of the best control efforts of plant pathologists. Breeding for disease-resistant varieties and the application of synthetic chemical fungicides are the most widely accepted approaches in plant disease management. CMN1308 strain of Bacillus amyloliquefaciens was isolated from healthy Chinese chestnut fruit, which has antibiosis and induced resistance to the prevention mechanism of pathogenic bacterium after picking. In order to evaluate the antibiosis mechanism, CMN1308 was fostered with the method of confront culture. The antimicrobial components were also isolated from the culture of CMN1308, and their stability and antimicrobial activity was tested under different treatments such as temperature, pH and UV. The results showed that CMN1308 displays advantages in regard to spatial competition against the major pathogens of chestnut, Rhizopus stolonifer, Fusarium solani, Stachybotrys chartarum, Cryphonectria parasitica, Lasiodiplodia theobromae, Penicillium expansum and Aspergillus niger. Among this, CMN1308 had the best antimicrobial activity against P. expansum, with the inhibition zone diameter of 27.1 mm. The antimicrobial material isolated from CMN1308 culture showed a strong inhibition to the growth of P. expansum hyphal and also had a good stability to high temperature, alkali media and UV, but was sensitive to acidic conditions. Furthermore, CMN1308 increased the peroxidase, polyphenol oxidase activity and reduced the MDA content in chestnuts after infecting by pathogenic fungi. Thus, producing antibiotic compounds and inducible resistance are the main factors that may explain the antibacterial mechanism of CMN1308 on chestnut pathogenic. The results of this study might help to optimize the practical use of CMN1308 in the biological control of chestnut rot or other fruit rot infected by pathogenic fungi.
Highlights
The Chinese chestnut (Castanea mollissima Blume) belongs to the Fagaceae family, being a traditional nut and one of the most popular foods across the world
Cryphonectria parasitica, Rhizopus stolonifer, Stachybotrys chartarum, Lasiodiplodia theobromae, Fusarium solani, Penicillium expansum, Aspergillus niger, which were kept on the PDA (Potato dextrose agar) culture at 25 °C, were isolated from the natural infected chestnut fruit collected (Hua, 2014)
The fermentation broth showed the best biological control to the four fungi, the infection rate was 28.3% to P. expansum, 35% to F. solani, 31.7% to C. parasitica and 50% to A. niger respectively, the sterile filtrates had a higher infection to the four fungi than the resuspension treatment
Summary
The Chinese chestnut (Castanea mollissima Blume) belongs to the Fagaceae family, being a traditional nut and one of the most popular foods across the world. The chestnut fruit is considered of high nutritional value and it has a long history of usage as a tonic food in traditional Chinese medicine (Borges et al, 2007; Zhang et al, 2011). Browning and postharvest diseases are serious technical trouble in chestnut processing (Zhou et al, 2015). This problem cause enormous economic loss in Asia. Synthetic fungicides are primarily used to control postharvest diseases of chestnut. The global trend appears to be shifting towards reducing the use of fungicides and there is a strong public desire to seek safer and eco-friendly alternatives for reducing the decay loss in the harvested commodities (Mari et al, 2007)
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