Abstract: F₁ progenies of‘Guinong 6’ ( resistant) בGuinong 5’ ( susceptible) and their reciprocal cross were used to investigate the inheritance tendency of resistance to powderymildew disease of chestnut rose (Rosa roxburghii Tratt). The result showed that the disease index of F₁ progenies showed normal distribution. Hereditaries ( T_a ) of F₁ progenies disease indexwere significantly higher than mid-parent value, and the broad-sense heretabilities of Guinong 6 ×Guinong 5 and the recip rocal crosswere 61.0% and 60.4% respectively. Based on the disease index, the F₁ progenies of Guinong 6 ×Guinong 5 could be grouped into three subclusters using UPGMA method, which revealed high resistance, moderate resistance, and susceptibility respectively, and their segregation ratios were 1∶2∶1 by X² test. These results suggest that the resistance appears to be co-dominated by two types of genetic models: 1) Two alleles which show additive effect between them; 2) Multiple genes which contribute to the continued values of disease index in same subcluster.

Key words: Chestnut rose (Rosa roxburghii Tratt), Powdery mildew, Disease index, Inheritance of resistance