霜疫霉侵染对不同荔枝品种果皮苯丙烷类代谢的影响

荔枝霜疫霉病是荔枝生产过程中的主要病害之一,严重影响荔枝品质和产量。本文以霜疫霉病抗病品种‘黑叶’和感病品种‘桂味’成熟果实为材料,研究霜疫霉悬浮孢子接种后果皮中苯丙烷类代谢通路相关酶活性及代谢产物含量的变化,分析苯丙烷代谢通路与荔枝对霜疫霉侵染抗性的关系。研究结果表明：抗、感病品种接种霜疫霉菌后,其苯丙氨酸解氨酶（PAL）和过氧化物酶（POD）活性均有不同程度的提高,且抗性品种‘黑叶’的POD活性高于感病品种‘桂味’。与之相反,‘桂味’的β-葡萄糖苷酶（BGLU）活性高于‘黑叶’。抗性品种‘黑叶’的总酚、类黄酮和花色素苷含量高于感病品种‘桂味’,而‘桂味’的香豆素含量高于‘黑叶’。接种霜疫霉菌后,总酚、类黄酮和花色素苷含量随贮藏时间的延长而逐渐下降,香豆素含量则有一定程度的升高。相关分析表明,上述指标与病情指数显著相关,暗示它们与荔枝对霜疫霉侵染的抗性密切相关。

Effects of Phenylpropanoid Metabolism in Different Litchi Varieties During the Infection of Phytophthora litchii

Litchi downy blight is the most serious disease in litchi, which leads to the yield and quality loss of fruit. In this work, the mature fruits of the disease-resistant variety ‘Heiye’ and the disease-susceptible variety ‘Guiwei’ inoculated with Phytophthora litchii infection were used to test the changes of enzymatic activities and metabolisms involved in phenylpropanoid metabolic pathway. The results indicated that the PAL (phenylalanine ammonia lyase) and POD (peroxidase) activity of the resistant and susceptible varieties increased following the infection of P. litchii. The activity of the two enzymes was higher in the resistant variety than that in the susceptible one. In contrast, the BGLU (beta-glucosidase) activity in ‘Guiwei’ was higher than that in ‘Heiye’. The contents of total phenols, flavonoids and anthocyanins in ‘Heiye’ were higher than that in ‘Guiwei’, and the contents of all the three types of metabolites in the two varieties decreased gradually with the extension of storage time. However, the content of coumarin increased in both cultivars. Correlation analysis showed that the enzyme activity and the content of phenylpropanoid metabolites were significantly correlated with the disease index, which suggested that the biosynthesis of phenylpropanoid metabolites is closely related to the resistance of litchi against P. litchii.