Growth and fruit production of tomato grafted onto wolfberry (Lycium chinense) rootstock in saline soil

Abstract

The process of grafting tomato onto salt-tolerant rootstock could improve tomato salt resistance, and grafting tomato onto the woody rootstock could allow the tomato plants to grow well. However, whether the tomato plants grafted on the woody halophyte could adapt to the coastal saline soil remained unknown. In this study, self-rooted tomato seedlings and tomato scions grafted onto wolfberry (Lycium chinense) rootstock that were planted in saline soil were studied. Tomato shoot growth, leaf gas exchange, chlorophyll fluorescence, leaf ion accumulation, and fruit yield and quality were analyzed. The results showed that both salt stress and grafting onto wolfberry rootstock significantly reduced tomato growth and fruit yield. In the nonsaline soil, grafted tomato shoot height, biomass and stem diameter were significantly lower than those in the self-rooted tomato plants, while in the saline soil, there were no significant differences in tomato shoot height, biomass and stem diameter between the grafted and self-rooted tomato plants. However, the stem diameter of the wolfberry rootstock was significantly smaller than that of the tomato scions. Salt stress significantly reduced the leaf chlorophyll index (SPAD) of the self-rooted tomato plants, but grafting onto wolfberry increased the tomato leaf SPAD value. Tomato leaf water potential was dependent on soil salinity, and grafting had no effect on leaf water potential. The leaf net photosynthetic rate, stomatal conductance and transpiration rate of the self-rooted tomato leaves in the saline soil were significantly lower than these of other treatments, while the self-rooted tomato in nonslaine soil was significantly higher than that of other treatments. The leaf florescence parameters indicated that the light use ability of the leaf chlorophyll was destroyed only in the self-rooted tomato plants in the saline soil, while the grafted tomato plants in saline soil remained unstressed. Tomato grafted onto wolfberry had significantly increased fruit fiber and soluble sugar concentration and reduced vitamin C concentration. Salt stress and grafting onto wolfberry rootstock significantly increased leaf Na+ accumulation, and the leaf Na+ concentration of the grafted tomato plants in saline soil was significantly higher than that in the other treatments. These results suggested that the growth and fruit yield of the tomato grafted on wolfberry were reduced but the union of tomato and wolfberry was not sensitive to salt stress. The growth and fruit yield of the grafted tomato plants were limited by the thinner woody stem. All the results suggested that tomato grafting on wolfberry was a feasible way for tomato fruit production in the coastal saline land of north China.