茉莉酸甲酯处理对脐橙果实青霉病及防御酶活性的影响

Effects of Methyl Jasmonate Treatment on Blue Mold and Defense Enzymes Activity of Navel Orange Fruit

【目的】试验以赣南‘纽荷尔’脐橙为试材,探究茉莉酸甲酯(MeJA)诱导脐橙果实抗青霉病效应及其与相关防御酶活性的关系,为MeJA应用于果实贮藏保鲜提供理论参考。【方法】接种前12,24,36,48 h分别用25,50,100,500,1000μmol/LMeJA熏蒸脐橙果实,接种浓度为1.25×10^(6)spores/mL青霉病菌(Penicilliumitalicum)孢子悬浮液,测定脐橙果实经MeJA预处理后病斑直径及相关防御酶活性。【结果】50μmol/L MeJA熏蒸处理24 h诱导脐橙果实抗青霉病效果最佳,其诱导效应为27.11%。与对照相比,50μmol/LMeJA熏蒸处理脐橙果实在接种后第8天病斑直径显著降低,诱导效果最佳,达20.87%,25,50,100,500,1000μmol/LMeJA其诱导效果依次为11.53%、8.20%、6.10%、4.60%和4.10%。脐橙果实经MeJA熏蒸处理24 h和36 h在发病第4~10天中其诱导效果均显著高于熏蒸12 h和48 h对照组。其中接种后第4天,熏蒸24 h和36 h诱导效果最佳,依次为27.11%和26.68%,显著高于熏蒸12 h和48 h诱导效果的11.52%和3.66%(P<0.05)。此外,在测定的相关防御酶活性中,接种后24~36 h的MeJA处理组过氧化物酶(POD)活性均显著高于对照组。MeJA处理组于接种后0~24 h多酚氧化酶(PPO)活性呈先上升后下降趋势,而MeJA处理组的超氧化物歧化酶(SOD)在接种后0~12 h活性较低,随着诱导时间延长,活性高于对照组。而抗坏血酸过氧化物酶(APX)和过氧化氢酶(CAT)活性一直保持较高水平,且48~60 h呈现升高趋势。MeJA处理组丙二醛(MDA)含量于接种后48~60 h开始降低,且接种后24~48 h能维持病程相关蛋白β-1,3葡聚糖酶(β-1,3-glucanase,GLU)和几丁质酶(CHI)较高活性。【结论】25~1000μmol/L MeJA于接种前12~48 h熏蒸脐橙果实,能增强果实防御能力,提高果实对青霉病的抗性和果实中防御酶POD、PPO、APX和CAT以及病程相关蛋白CHI、GLU活性,降低MDA含量,延缓膜脂过氧化。上述结果暗示MeJA处理能抑制脐橙果实青霉病的发生可能与其提高防御酶活性和病程相关蛋白酶的水平有关,可为柑橘果实采后贮藏保鲜提供理论依据和技术参考。

[Objective]This experiment was implemented to investigate the effect of Methyl jasmonate(MeJA)inducing resistance to blue mold and its relationship with related defense enzymes activity in navel orange fruits from Gannan,which aims to provide theoretical references for the application of MeJA in fruit storage and preservation.[Methods]Navel orange fruits were fumigated with 25,50,100,500 and 1000μmol/L MeJA at 12,24,36 and 48 h before inoculation with a concentration of 1.25×10^(6)spores/mL of Penicillium italicum suspension.The lesion diameters and related defense enzymes activity were measured after treatment with MeJA in navel orange fruits.[Results]50μmol/L MeJA fumigation treatment for 24 h showed the optimal effect on resistance to blue mold of navel orange fruit,and the induction effect was 27.11%.Compared with the control,navel orange fruits with 50μmol/L MeJA fumigation treatment showed a significant reduction in lesion diameter at the 8th day after inoculation with the best induction effect of 20.87%,while the effects of 25,50,100,500 and 1000μmol/L MeJA were 11.53%,8.20%,6.10%,4.60%and 4.10%respectively.The induction effects of navel orange fruits treated with MeJA for 24 h and 36 h were significantly higher than those of the 12 h and 48 h fumigation groups in the 4th-10th day of inoculation.On the 4th day after inoculation,the induction effect of 24 h and 36 h fumigation were the optimal with 27.11%and 26.68%respectively,which was significantly higher than those of 12 h and 48 h fumigation and the effects were respectively 11.52%and 3.66%(P<0.05).Furthermore,the peroxidase(POD)activity of the MeJA group was significantly higher than that of the control group from 24 to 36 h after inoculation.The polyphenol oxidase(PPO)activity of the MeJA treated group showed an increasing and then decreasing trend from 0 to 24 h after inoculation,while the activity of superoxide dismutase(SOD)of the MeJA treated group was lower than that of the control group.As the induction time lengthened,the activity began to increase and was higher than that of the control group,while the activity of ascorbate peroxidase(APX)and catalase(CAT)remained a high level,with an increasing trend at 48-60 h.In the MeJA group,the malondialdehyde(MDA)content started to decrease at 48-60 h after inoculation.Moreover,β-1,3-glucanase(GLU)and chitinase(CHI)were maintained at a high level at 24-48 h after inoculation.[Conclusion]Fumigation with 25-1000μmol/L MeJA at 12-48 h before inoculation enhanced defense of navel orange fruit by increasing the activity of defense enzymes POD,PPO,APX,CAT,CHI and GLU of the fruits and reducing MDA content and delayed membrane lipid peroxidation.The above results suggest that MeJA treatment could inhibit the occurrence of blue mold in navel orange fruits,which may be related to the defense enzymes activity and provide theoretical basis and technical reference for postharvest storage and preservation of citrus fruits.