Determination Of Resistance And Evaluation Disease Resistance Of Primary Cultivars In Yunnan

In recent years, the tobacco bacterial wilt is occurred severely in the south of Yunnan provience, especially in Wenshan county. The incidence of this disease reached 80% in partial area and lead to the death of tobacco at the serious condition. In 2007, Samples of tobacco bacterial wilt were gathered and pathogenicity of various strains were inspected, the resistance to tobacco bacterial wilt of nine main varieties in the field performanca was analyzed and appraised , at the same time the yield ,the value and chemical components of tobacco leaf were appraised systemically. The results were as fellows:1.91 strains of Ralstonia solancearum were isolated from 170 gathered disease samples, according to their pathogenicity to detached leaves of tobacco variety K326, these strains were divided into three groups of strong, middle and weak virulence. According to different reactions on 4 differential tobacco varieties(Hongda, K326, Yunyan97 and Yunyan85), Strain tested can be divided into 3 different pathotypes.2.Among 56 strains chosen in six county of Yunnan province, pathotypeâ… is dominant, followed by pathotypeâ…¡, pathotypeâ…¢in the percentage of 63.6%, 27.3% and 9.1%,respectively. The geographical distribution of three pathotype representative strains were difference obviously.3.To determine the resistance of 9 cultivars (K326, Yunyan97, Yunyan85, Yunyan201.etc ) tobacco varieties to bacterial wilt, the pathogenicity was assessed under the inoculated and natural condition. The results indicated that K326, Yunyan87 and Yunyan201 were with higher resistant ability, Yunyan85, K346, Yunyan203 and Yunyan97 were with lower resistant ability, and hongda and NC82 were with the lowest resistant ability. The disease resistance of various cuhivar was K326>Yunyan201> Yunyan87 > Yunyan85 > K346, Yunyan203 > Yunyan97 > NC82 > hongda.