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Background : In the process of developing new disease-resistant cultivar of Rehmannia glutinosa, it is essential to screen plants based on resistance to their disease. But until now, we have relied on visual inspection for selection of disease-resistant cultivar. Therefore, this experiment was carried out to establish an efficient and reliable screening system and test the resistance to leaf spot disease in R. glutinosa cultivars developed until now.
Methods and Results : We have tested 11 R. glutinosa cultivars developed so far. Rootstock of R. glutinosa were sown in 20 × 20 ㎝ plastic square port and grown in green house at 25 ± 5℃ for four months and then cutting leaves were inoculated with Phoma sp. HCRD 17103 by spraying spore suspention of fungus at concentration of 1 × 107 spore/㎖. The inoculated leaves were incubated in a dew chamber at 25℃ for 48h and then transferred to glass house (25 ± 5℃, RH 80% ≥ ). After 3 - 5 days when the most susceptible cultivar had lesion area over 40%, disease severity of the cultivars was investigated on a scale of 0 - 9 (0 = healthy, 1 = 0 - 1%, 3 = 1.1 - 10%, 5 = 10.1 - 20%, 7 = 20.1 - 40%, 9 = 40.1% over). The degree of resistance was determined according to the disease index (0 and 1 = resistant, 3 = moderately resistant, 5, 7 and 9 = susceptible). As a result of experiments according to the above criteria, the disease index of cultivar Gogang, Dagang, Segang, Yeongang, Wongang, and Dahwang was 1, cultivar Togang, Daegyung, Jiwhang 1 and Goryeo was 3, cultivar Hwanggang was 9, respectively.
Conclusion : From the above results, six cultivars such as Gogang, Dagang, Segang, Yeongang, Wongang, and Dahwang were resistant, four cultivar such as Togang, Daegyung, Jiwhang 1 and Goryeo were moderately resistant, and only one cultivar Hwanggang was susceptible to the leaf spot disease by Phoma sp. This experiment used only leaves and we plan to use whole plants in the future to see more accurate resistance response.
