Physiological Response of Different Cucumber Hybrid Combinations to Inoculation of Powdery Mildew

Abstract

In order to study the physiological changes of different cucumber combinations in South China to powdery mildew, on the 0, 1, 3, 6 and 9 days after inoculation of powdery mildew, the changes of disease index, chlorophyll content, defense enzyme activity and osmoregulation substance content of 5 South China hybrid combinations were studied, and relationship between the changes of physiological indexes and the resistance of cucumber powdery mildew was analyzed. The results showed that, according to the disease index, the resistance of 5 cucumber combinations was graded, 18C-3 was disease resistance, 18C-2 and 18C-4 were medium resistance, 18C-1 and 18C-5 were susceptible; after inoculation of 5 cucumber combinations with powdery mildew, the content of chlorophyll decreased, and the content of chlorophyll in 18C-3 was higher than that in other combinations; The activity of superoxide dismutase (SOD), peroxidation(POD) and phenylalanine ammonia lyase (PAL) of most combinations decreased first, and then increased. the activity of polyphenol oxidase (PPO) was up – down – up again. The activity of defense enzyme of resistant combination 18C-3 was significantly higher than that of other combinations, and maintained high proline (PRO) content and low malondialdehyde (MDA) content all the time, indicating that the resistant combination had stronger defense ability and resistance to membrane lipid peroxidation than the susceptible combinations. By analyzing the changes of physiological indexes and the relationship with resistance to powdery mildew of cucumber, the resistant combination of South China type was selected, which provided more theoretical basis for resistance identification and genetic breeding of cucumber powdery mildew.