Abstract:

Comparative analysis between two potato cultivars was carried out to detect the key enzymes activities and
metabolite accumulation in phenylpropanoid pathway in whole and sliced potatoes inoculated with Fusarium sulphureum.
The results showed that lesion diameters on tubers and slices of the resistant cultivar “Qingshu No.168” inoculated with
F. sulphureum were significantly smaller than those of the susceptible cultivar “Longshu No.3”. The activities of phenylalanine
ammonia-lyase (PAL) and 4-coumarate A ligase (4CL), and the contents of total phenolics and flavonoids in inoculated slices
of both potato cultivars increased at early stages of infection but decreased sharply with the enlargement of lesions, reaching
levels lower than in the control at later stages of infection. However, the activity of cinnamate 4-hydroxylase (C4H) and the
content of lignin were lower than in the control over the entire culture period. The activities of PAL, 4CL, and C4H, and the
contents of total phenolics, flavonoids and lignin in inoculated slices of “Qingshu No.168” were higher than those of “Longshu
No.3”. These findings suggested that phenylpropanoid metabolism played a positive role at early stages of F. sulphureumpotato
interaction; however, the resistance role of phenylpropanoid metabolism decreased with the expansion of dry rot, and
the activities of phenylpropanoid metabolism in slices of the resistant potato cultivar were significantly higher than in the
susceptible one, indicating that phenylaprapanoid metabolism plays an important role in resistance of potato tubers against
F. sulphureum.

Key words: potato, Fusarium sulphureum, inoculation, phenylpropanoid metabolism