Grafting on rootstocks with low Cd accumulating potential: A green technology in vegetable production

Recently, grafting with certain rootstock cultivars has been observed to significantly reduce Cd accumulation in above ground plant tissues. However, the mechanism remains unclear. This study comprehensively evaluated the influencing factors and their contribution in affecting Cd uptake and translocation in grafted tomato plants. One tomato scion cultivar 'Jingcai 8' was grafted onto two rootstock cultivars 'Guozhen 1' and 'Zhenai 1' to evaluate the grafting effect on plant Cd uptake and translocation on Cd contaminated soil. The results demonstrated that grafting with 'Guozhen 1' and 'Zhenai 1' significantly enhanced plant growth and fruit biomass. Grafted rootstocks recruited microbes, which reduced rhizosphere Cd bioavailability. However, the reduction of soil Cd bioavailability was offset by enhanced root growth which contributed to root Cd uptake. The significantly increased root biomass and fine root length in the rootstocks resulted in significantly higher root Cd uptake than in the non-grafted treatment by 6.35-20.40 %. Nevertheless, grafting with 'Zhenai 1' had a significantly low translocation of Cd from root to fruit (TF of 0.015) than the non-grafted treatment (TF of 0.019), which resulted in a significant reduction in fruit Cd content by 17.54 %. This was due to the effects of grafting with rootstock 'Zhenai 1' that reduced Cd mobility by increasing GSH and decreasing subcellular distribution in cytoplasm. Fruit Cd content was the net result of root uptake and translocation. These results showed that grafting with a suitable rootstock is a promising green and low-cost approach for the production of safe vegetables on Cd-contaminated soil.