Pathogenicity of dried-shrink disease and evaluation of resistance in a germplasm collection of sea buckthorn (Hippophae L.) from China and other countries

Sea buckthorn (Hippophae L.) is a woody, dioecious plant that can be grown in dry and poor soil conditions. It has recently received world-wide attention as a new berry crop with a very high nutritional value and unique medicinal properties, as well as a means of combating soil erosion. A major problem is, however, dried-shrink disease (DSD), which destroys sea buckthorn plants and halts commercial production. In this study, we investigated symptoms and pathogenicity of DSD, isolated and identified pathogens using a combination of morphology and ITS sequences, and evaluated the disease index (DI) of different cultivars in the field. DSD infection causes isolated yellowing of plant tissues, and as the disease develops the bark putresces, dries and shrinks, and finally the plant dies. DSD infects older plants (>3 years), often at the plant base. Death of plant parts above the infected area does not influence root vitality, and a new plant can therefore be regenerated. Combining morphological characters and ITS sequences, we isolated and identified four fungal pathogens causing DSD, including Fusarium acuminatum, F. oxysporum, Fusarium camptoceras and Phomopsis spp. DI values for 27 cultivars ranged from 0 to 10.4. About half of the cultivars were regarded as resistant (DI < 3.2) to DSD, and half as susceptible (DI > 6.7). Cultivar ‘Zhongguoshaji’ (DI = 4.2) showed an intermediate level of DSD resistance. Our data provides basic information for further studies of the mechanism of pathogenicity, and for breeding of DSD-resistant cultivars.

Research highlights▶ DSD infection causes the bark putresces, dries, shrinks, and finally dies. ▶ DSD infects plants, often on the tree-neck, when plants are over 3 years old. ▶ Infected tree-neck do not influence root vitality that can regenerate a new plant. ▶ Four fungal pathogens causing DSD were isolated and identified. ▶ Disease index of DSD of 27 cultivars ranged from 0 to 10.4.