Physiological changes of litchi fruit infected by Peronophythora litchi

chinois. 人工接种霜疫病菌的荔枝果实感病后，病斑部位的果皮和距离病斑部位较近的果皮中O2产生速率和MDA含量较高，而SOD活性较低；距离病斑部位较远的果皮中O2产生速率和MDA含量较低，而SOD活性较高；邻近病斑部位的果皮中PPO、POD和PAL活性较高，而距病斑部位较远的果皮中PPO、POD和PAL活性较低。表明霜疫病菌的侵染对荔枝果皮中以SOD为核心的活性氧清除酶系统产生了破坏作用，导致SOD活性下降，使得自由基等活性氧与其清除系统之间的相对平衡被破坏，启动膜脂过氧化，膜脂过氧化产物MDA含量显著增加，造成对细胞的伤害，加速荔枝果实衰老和劣变。同时霜疫病菌侵染诱导荔枝果皮中POD、PPO和PAL活性增高，是加速荔枝果皮酶促氧化褐变的一个重要原因。

anglais. South China Agricultural University, Guangzhou (China), College of Horticulture After inoculation with Peronophythora litchi, the disease was developed and the production rate of superoxide radical anion(O-2) and the content of malondialdehyde (MDA) were found to be increased in and near the infected parts on litchi pericarp, while the activity of superoxide dismutase (SOD) was decreased ;but the situations were just opposite in the positions far from the infected parts on litchi pericarp. The activities of polyphenoloxidase (PPO), peroxidase (POD) and phenylalanine ammonia-lyase (PAL) were enhanced near the infected parts on pericarp, but reduced far from them. It suggested that the infection of Peronophythora litchi destroyed the active oxygen removing enzyme system with SOD as its core enzyme, thus inducing the drop of SOD activity. The relative balance between the active oxygen such as free radical and its removing system was desdroyed, lipid peroxidation initiated and the content of lipid peroxidation reactant was increased markedly. Such process damaged the cells and accelerated the senescence and decay of litchi fruit. Meanwhile, the infection of peronophythora litchii induced activities of POD, PPO and PAL on litchi pericarp, being one of the most important reasons to accelerated the enzymic browning of litchi pericarp.