Calcium uptake and resistance to bacterial wilt of mutually grafted tomato seedlings

Bacterial wilt of tomato (Lycopersicon esculentum Mill.) caused by Ralstonia solanacearum Smith is a serious disease in Japan. We previously reported that calcium (Ca) nutrition in tomato significantly affected the resistance to the disease, and that highly resistant cultivars were characterized by a high Ca uptake. We examined the relationship between the Ca uptake and resistance using mutually grafted seedlings of tomato cultivars differing in their resistance. A susceptible (‘Ponderosa’) or moderately resistant (‘Zuiei’) cultivar (scion) was grafted on the rootstock of a susceptible, moderately resistant, or highly resistant cultivar (‘Hawaii 7998’). Roots or petioles of the grafted seedlings were inoculated with the pathogen, and the development of bacterial wilt was observed. Although Ca uptake by shoot increased by grafting on the rootstock of a highly resistant cultivar, the development of the disease was not influenced by the difference in Ca uptake, and depended on the resistance of the cultivar to which the inoculated part of the graft belonged. It was concluded that the differences in Ca uptake of the shoot of the grafted tomato seedlings might not be related to the expression of the resistance to bacterial wilt.