Study of combined field tests and selections for rust disease resistance in zoysiagrass

To evaluate the effectiveness of previous screening of rust disease resistance, germplasm and disruptive selection in zoysiagrass, three identified groups including resistant, susceptible and control lines were assessed for percent incidence and percent severity of rust disease in Jiaozhou, Shandong Province in 2010 and 2011, and in Yangzhou, Jiangsu Province in 2011, respectively. A combined analysis was conducted under same location and multiple environment conditions, in which a location under one year was considered as one environment condition. 24 and 21 tested lines evaluated at Jiaozhou in 2010 and 2011, respectively, and 42 tested lines were evaluated at Yangzhou in 2011. The results indicated that extremely significant difference was showed among resistant, susceptible and control groups (P0.001). Compared with control lines, both selections toward resistant and susceptible have made a significant effect. Within same group, differences of percent incidence and/or percent severity between tested lines were extremely significant (P0.001) or significant (P0.05). There were significant differences among blocks for percent severity in Jiaozhou in 2010 (P0.05) and no significant differences between percent incidence and percent severity was indicated within blocks in Yangzhou and Jiaozhou in 2011(P0.05). By a combined multiple environment conditions analysis for 5 tested lines, there were significant differences among percent incidence of rust disease observed within locations, among tested lines and interaction of locations and tested lines in zoysiagrass (P0.001), and no significant differences among blocks (P0.05). Above results demonstrated that occurrence of rust disease in zoysiagrass varied between locations and years. Under the same environmental condition, significant difference in resistance could be contributed to genotype effects other than environment effect. Out of these tested lines, a line coded as 111 which collected from Jiaodong peninsula possessed a total immune resistant in all two locations in 2010 and 2011. In addition, a line coded 83 showed necrosis symptom around rust infection point, suspected as a slowrusting material. These promising materials provide ideal lines for genetics and breeding program in the future for zoysiagrass rust disease.