Combined effect of Bacillus siamensis and chlorogenic acid on maintenance of quality and control of disease in stored wax apple fruit

Objectives:The purpose of this study was to evaluate the effect of combined postharvest use of Bacillus siamensis strain and chlorogenic acid on quality maintenance and disease control in wax apple fruit.Materials and Methods:Wax apple fruit were treated with Bacillus siamensis strain(N1),chlorogenic acid(CHA)and N1+CHA and preserved at 25℃ for 12 d.The appearance and quality parameters were evaluated,along with the disease index,content of total soluble solids(TSS),total acid(TA),vitamin C(Vc),total phenolic,and flavonoids during cold storage.Meanwhile,the activities ofβ-1,3-glucanase(GLU),phenylalanine ammonialyase(PAL),polyphenol oxidase(PPO),and peroxidase(POD)were determined.Furthermore,the transcriptome and the expression level of key defense enzyme genes were analyzed by RNA-seq and real-time quantitative reverse transcription polymerase chain reaction.Results:N1+CHA treatment significantly lowered DI and delayed fruit quality deterioration by slowing TSS and TA loss and enhancing anti-oxidant capacity,including Vc,total phenolic,and flavonoids content.Meanwhile,the activities of GLU,PAL,PPO,and POD were dramatically increased by N1+CHA treatment.Additionally,N1+CHA treatment modulated several metabolic pathways,including those involved in planthormone signal transduction and plant–pathogen interaction.The expression levels of key defense enzyme genes were significantly upregulated in stored wax apple fruit by the N1+CHA treatment,which were well coincided with the transcriptome data.Conclusions:The combined use of N1+CHA significantly prevents disease and maintains fruit quality of wax apple during storage.These findings indicate that it could serve as a promising biological technique for preserving wax apple fruit.