Fumigant activity against anthracnose pathogen in postharvest chili fruit

Application of volatiles from Streptomyces philanthi RM-1-138 grown on sterile wheat seeds (volatiles RM-1-138) and pure commercial volatile compounds (acetophenone and phenylethyl alcohol) against chili anthracnose pathogen were investigated in vitro and in vivo. Among 42 isolates of Colletotrichum species tested, C. gloeosporioides PSU-NY8 was selected as the most aggressive anthracnose pathogenic strain on chili fruit against the volatiles RM-1-138. The optimum inoculum size (15 g L?1) and spore concentration (107 spore mL?1) of the wheat seed culture of S. philanthi RM-1-138 exhibited the complete suppression (100% inhibition) on C. gloeosporioides PSU-NY8. In addition, the in vivo result indicated the optimum fumigation period of the volatiles RM-1-138 (15 g L?1) was at 6 h. Phenylethyl alcohol showed no antifungal activity at all concentrations tested (10?1000 ?L L?1) while acetophenone at 100 ?L L?1 of airspace exhibited antifungal activity both in vitro and in vivo after 12 h fumigation. The fumigant activity was evidenced by the damage of cell wall of C. gloeosporioides PSU-NY8 illustrated by SEM. Therefore, the volatiles from S. philanthi RM-1-138 have a high potential for biocontrol of chili anthracnose disease in postharvest system. Chili belong to the genus Capsicum annuum L. (Solanaceae family) is an important vegetable crop in Thailand, but production has gradually decreased during the last few decades by infection with anthracnose disease. This disease is caused by fungi such as Colletotrichum gloeosporioides and C. capsici (Chanchaichaovivat et al., 2007, 2008) and is the major prevalent and widespread postharvest diseases affecting the marketability of chili fruit (Nantawanit et al., 2010). In particular, the reduction of marketable yield by 10%?80% from species of Colletotrichum was reported in some developing countries i.e. Thailand, Turkey, Pakistan (Than et al., 2008; Maharaj and Rampersad, 2012; Katoch et al., 2017). Control of chili anthracnose pathogens by using chemical fungicides could cause the fungicide-resistant pathogens (Parry, 1990) and the risks to consumers and environment (Dedej et al., 2004; Pal and Gardener, 2006; Chanchaichaovivat et al., 2008). Biological control by microbial antagonistic agents is widely recognized as a promising approach to replace chemical fungicides to control postharvest diseases (Janisiewicz and Korsten, 2002; Nantawanit et al., 2010). Antagonistic bacteria such as Bacillus pumilus and B. thuringiensis (Zheng et al., 2013) and Streptomyces spp. (Li et al., 2010, 2012; Wang et al., 2013), fungi such as Muscodor suthepensis CMU-Cib462 (Suwannarach et al., 2015), or yeast such as Pichia guilliermondii R13 (Nantawanit et al., 2010) were reported to produce effective volatile compounds for controlling the anthracnose disease under the specified conditions (Strobel and Daisy, 2003). Technical grade volatile compounds to control plant pathogenic fungi were also previously reported, for examples, using dimethyl disulfide and dimethyl trisulfide (at 100 ?L L?1) to control Penicillium italicum and Fusarium moniliforme on Citrus microcarpa (Li et al., 2010; Wang et al., 2013), isovaleric acid, isobutyric acid and isoamyl alcohol showed complete inhibition on the growth of Alternaria alternata (You et al., 2015). The 2-nonanone, 2-decanone, and ?-benzene ethanamine at 100 ?L L?1 could suppress the postharvest anthracnose disease of mangos caused by C. gloeosporioides (Zheng et al., 2013). Volatile compounds from wheat seed culture of Streptomyces philanthi RM-1-138 was able to control the rice sheath blight disease caused by Rhizoctonia solani (Boukaew et al., 2013). This study aims to apply S. philanthi RM-1-138 volatiles as a biofumigant to inhibit the selected aggressive strain of Colletotrichum species, the anthracnose pathogen, in postharvest chili fruit and compared to the two pure chemical volatiles (acetophenone and phenylethyl alcohol) as well as to find the optimum fumigation period of the S. philanthi RM-1-138 volatiles and acetophenone to control chili anthracnose pathogen. Access to document 'Fumigant activity of volatile compounds of Streptomyces philanthi RM-1-138 and pure chemicals (acetophenone and phenylethyl alcohol) against anthracnose pathogen in postharvest chili fruit'? Source:(a) Sawai Boukaew, Wanida Petlamul, Ruthaiwan Bunkrongcheap(b) Teera Chookaew(c) Thai Kabbua, Apinya Thippated (d) Poonsuk Prasertsan (a) College of Innovation and Management, Songkhla Rajabhat University, Songkhla, Thailand(b) Biotechnology Research & Development Office, Department of Agriculture, Ministry of Agriculture & Cooperatives, 50 Phaholyothin Rd., Bangkok, Thailand(c) Division of Environmental Science, Faculty of Liberal Arts & Science, Sisaket Rajabhat University, Sisaket, Thailand(d) Department of Industrial Biotechnology, Faculty of Agro-Industry, Prince of Songkla University, Songkhla, 90112, Thailand