Résumé
Aims: The paper aimed to clarify the effect of cucumber target leaf spot (TLS) under the Jingdusha (JDS) treatment. Study Design: We applied the method of artificial inoculation in the pot, and analyzed the changes in growth indexes and physiological characteristics. Place and Duration of Study: In 2018, these experiments were conducted in College of Bioscience and Biotechnology of Shenyang Agricultural University (Lab 240). Methodology: The seedlings in the two-leaf period were induced by the best application scheme of JDS, then inoculated Corynespora cassiicola for 24 h. Cucumber seedlings of each treatment group were randomly selected for photographing and growth index determination after inoculation for 5 d. The leaves of cucumber seedlings in each treatment group were randomly collected at 1 d, 3 d, 5 d, 7 d, and 9 d after inoculation for the determination of physiological and biochemical indicators. Results: When C. cassiicola infects cucumber, JDS can effectively improve the growth and photosynthetic pigment content of cucumber, reduce the degradation of chlorophyll (Chl) under the stress of C. cassiicola, strengthen the variety of metabolic responses in the plant, repair the enzyme protection system of cucumber leaves, reduce the accumulation of reactive oxygen species, shorten the process of membrane lipid peroxidation in blades. Conclusion: Taken together, these results suggest that JDS can improve the resistance of cucumber seedlings to C. cassiicola by regulating growth indexes and physiological characteristics. This work will provide a theoretical basis for further elucidating the molecular mechanism of JDS in cucumber defense against C. cassiicola.
Résumé
A leaf spot of cotton rose (Hibiscus mutabilis) occurred severely in the flower beds of cotton rose around Uiryeong-gun, Gyeongnam Province in Korea. The causal fungus was identified as Corynespora cassiicola on the basis of cultural and morphological characteristics of the fungus. The fungus grew well on potato dextrose agar and the colony color was gray to brown. Conidia were solitary or catenate, obclavate to cylindrical in shape, and pale olivaceous brown or brown in color. They had 420 pseudosepta, and measured 35.2~173.6 x 8.8~19.9 microm. Conidia germinated as a bipolar type. Conidiophores were pale to mid brown in color, and measured 74.2~275.6 x 3.8~10.8 microm. Optimal temperature for mycelial growth was 30degrees C. The fungal isolate grown on PDA showed strong pathogenicity to cotton rose plant. This is the first report on the corynespora leaf spot of cotton rose (Hibiscus mutabilis) caused by Corynespora cassiicola in Korea.