Regulation Effect Of Sulfur-containing Substances On Disease Resistance And Ripening And Senescence Of Peach Fruit

Peach [Prunus persica(L.) Batsch] which have quick mature and softening features after postharvest storage are climacteric fruit, and are highly susceptible to Monilinia fructieola infection to large losses in the storage and logistics. So, looking for safe treatment to reduce the losses is necessary. 'Mengyin' peach('Mitaowang') was used as material. Sulfur compounds including H2 S and HT which have not residual toxicity after applied in postharvest fruit were used for controlling Monilinia fructieola disease. Through the physiological and molecular methods, the effects of the two sulfur-containing substances on enhancing defense-related enzymes activities, including chitinase(CHI), ?-1,3-glucanase(GNS) and phenylalanine ammonialyase(PAL), and the expression of related genes(CHI, GNS and PAL) were studied. After the better sulfur-containing substance was selected, the mechanisms of disease resistance with sulfur compounds were investigated through the determination of the related antioxidant enzymes activities and the content of H2 S. What's more, the selected sulfur-containing substance was used for studying its delaying maturation and senescence mechanisms through the physiological methods. It is expected that technological assistance and theory evidence are supported for application of sulfur compounds in postharvest fruit. Main results of this research are as follows:(1) Mycelial and spore of M. fructicola were treated with different concentrations treatment(25, 50, 75 and 100 mmol L-1 NaHS, 0.1 and 1.0 mmol L-1 HT), which then returned to peach fruit to observe the pathogenicity of M. fructicola. It was found that four concentrations of NaHS could inhibit mycelial diameter, spore germination rate and pathogenicity of M. fructicola, and 50 mmol L-1 NaHS had better effect on inhibition of mycelial diameter and pathogenicity of M. fructicola. However, there was no inhibition effect for mycelial diameter, spore germination rate and pathogenicity of M. fructicola with 0.1 or 1.0 mmol L-1 HT.(2) Peach fruit were fumigated with 50 mmol L-1 NaHS solution and dipped in 0.1 mmol L-1 HT solution for 2 h respectively, and then inoculated by the spore suspension of Monilinia fructieola(5×105 spores mL-1) before observing the conditions(decay rate and lesion diameter) after 24, 48 and 72 h. It turned out that 50 mmol L-1 NaHS could inhibit lesion diameter and decay rate only at early time of incidence, and HT had a better inhibition effect. Peach fruit with above treatments were used to measure the defensed enzymes activities including phenylalnine ammonlalyase(PAL), chitinase(CHI) and ?-1,3-glucanase(GNS) activities(2 h, 12 h, 24 h, 48 h and 72 h). What's more, two related stable internal genes were chosen to been the reference of other genes expression about defensed enzymes genes using qRT-PCR. Both the two sulfur-containing substances could increase the three defensed enzymes and the related genes expression of defensed enzymes. Finally we found that HT had obvious effects to improve the defensed enzymes and genes expressions.(3) 0.1 mmol L-1 HT was used for treating peach fruit before inoculating Monilinia fructieola, and then the content of internal H2 S and antioxidant enzyme activities(SOD?PPO and POD) were determined. The results proved that HT could increase the content of internal H2 S and the three activities of antioxidant enzymes, which indicated that HT might increase disease resistance through increasing the content of H2 S and the activities of antioxidant enzyme.(4) It was found that treatment with 0.1 mmol L-1 HT on peach fruit(‘Fengcheng') could delay the rise of brown index and decline of firmness after storing at 0 °C condition, inhibit the respiration intensity, decrease ethylene content, prolong the peak of respiration rate and ethylene production, maintain higher content of Vitamin C and lower contentof TSS compared with control. In addition, HT treatment could increase the three activities of the related antioxidant enzymes compared with control which proved that HT had not a negtive effect on the quality of peach fruit, but also improved the antioxidant ability of peach fruit(‘Fengcheng') and prolonged the storage time.