Abstract: 【Objective】The objective of this study is to investigate the influence of grafting on cotton resistance to Verticillium wilt and to clarify the resistance mechanism of cultivated cotton species, which should be benefit to further understand the disease resistant mechanism and to breed new cotton resistant varieties. 【Method】 Six cotton varieties with different resistances to Verticillium wilt were selected based on previous research. Each variety was self and mutual grafted, and the direct sowing cotton was used as control. The disease occurrence and severity of direct sowing cotton varieties, self-grafted cotton lines and mutual grafting cotton lines were identified and compared in field trials. 【Result】 The disease index and incidence of direct sowing cotton varieties and their self-grafted cotton lines were not significantly different. The average disease index of materials with resistant island cotton varieties as scions were significantly lower than that of materials with resistant upland cotton varieties as scions, however, the average disease index of materials with upland cotton resistant varieties as rootstocks were significantly lower than that of materials with island cotton resistant varieties as rootstocks. And the tendency of disease incidence was the same as disease index.【Conclusion】The grafting operation doesn’t make any significant influence on cotton resistance to Verticillium wilt. The resistance mechanism of the island cotton species is different to that of upland cotton species. The critical organism resistant to Verticillium wilt should be stem in the case of resistant island cotton varieties, but in the case of resistant upland cotton varieties the critical organism resistant to Verticillium wilt should be root.

Key words: cotton, Verticillium wilt, graft, resistance mechanism