Time-course analysis of the accumulation of phenols in tomato seedlings infected with Potato Virus X and Tobacco mosaic virus

Abstract

The cotyledons of 3 –true leaf potted seedlings of a common Japanese tomato (i.e. cv. Fukuju No. 2) were mock inoculated with buffer only or singly and doubly with potato Virus X (PVX) and/or an attenuated strain (L11A) of tobacco mosaic virus (TMV-L11A) in greenhouse experiments. Time-course analysis of the methanol-extractable free, and saponifiable ester-bound phenol contents, as determined by the Folin-Ciolcalteau method, showed significantly higher accumulation in the primary leaves during the first 3 days in both mock and viral inoculated plants compared to the uninoculated controls. Whereas, however, the level in the healthy plants remained at about the same level thereafter, that in the infected plants continued to increase steadily peaking between 6 and 10 days postinoculation (dpi). Single infection induced significantly more free phenol accumulation than mixed infection at the peak period. The mean daily level of ester- bound cell wall phenols was about 12 – 20 times lower than that of the free phenols. It increased steadily in infected plants doubling its initial concentration as at 12 dpi but remained relatively unchanged in the healthy plants in the course of development. In contrast to the trend for methanol extractable free phenol accumulation, mixed infected plants had higher contents of saponifiable phenols than singly infected ones. Thin layer chromatography on silica gel G of the extracts from samples obtained at 12 dpi revealed at least 5 distinct bands (spots) that were common to both healthy and infected plants. However, the appearance of some extra bands that were highly florescent under long wave (320 nm) ultraviolet light on non florescent background silica gel, also indicating their phenolic nature, were limited to infected plants only. This indicates that viral infection not only affected the quantity but may also have altered the type of phenol components of the infected tomato plants.

Key Words: Tomato cv. Fukuju No. 2, mock and viral inoculations, phenolic components

Biokemistri Vol.16(2) 2004: 112-120