Studies On The Application And Molecular Mechanism Of Carbonyl Sulfide Fumigation Against Alternaria Alternata(Fr.) Keissler

The toxicity of carbonyl sulfide (COS) to stored products pests has been well studied as a potential alternative of methyl bromide for insect disinfestations, however, little is known about the efficacy of COS for control of fungal pathogens causing postharvest diseases of the fresh products.. The molecular mechanism of its toxicity is currently empty.Fumigation of pear fruit with COS at several concentrations, times and temperatures was studied for control of Alternaria alternata (Fr.) Keissler and to determine the effects on the quality of treated fruits. Our results showed that the fungitoxicity of COS became higher as the treatment temperature and time were increased, COS concentrations of 72.7 g/m³,117.8 g/m³ and 174.5 g/m³ resulted in 50%, 90% and 99% inhibition in vitro after four hours fumigation at 25℃, respectively. Furthermore, four hours COS fumigation repressed A. alternata in wounded pears at the dosage of 200 g/m³ at 25℃, indicating that control of this fungal pathogen with COS is achievable.COS fumigation was performed at different doses at 25℃on ya pears for 4hours and the quality parameters of pears were measured after stored at 25℃in order to study the influence of COS fumigation on the quality of ya pears. The results showed that COS fumigation could promote respiration during the treatment, reduced the water loss, While the quality parameters of flesh firmness, total soluble sugar and total acidity were not significant affected during storage at 25℃. When loading rate was about 50%, carbonyl sulfide fumigation at the dosage of 60 g/m³ for 4 hours can cause slight surface injury.In order to investigate the molecular mechanism of the fungitoxicity of COS, suppression subtractive hybridization (Suppression subtractive hybridization, SSH) was successfully proformed to construct the subtracted cDNA libraries and find the differentially expressed genes after COS fumigation. Sequence analysis showed that expression of several signal transduction-related genes involved in protein phosphorylation, calcium ion response were rapidly increased after 0.5 hours fumigation with COS , expression of several genes involved in cell protein synthesis, the process of proliferation-related genes were decreased after 1 hours fumigation with COS, indicating COS may activate a series of signal transduction to inhibit protein synthesis, cell division and proliferation of Alternaria alternata. Furthermore, expression of several genes involved in the metabolism of hydrogen sulfide and cysteine are rapidly increased after 0.5 hours fumigation with COS, indicating COS may form H₂S in the cells and kill Alternaria alternate directly.