Italian ryegrass (Lolium multiflorum Lam.) is one of the most widely grown winter forage crops in Korea, but its yields are known to be greatly affected by drought that occur frequently in spring. This study aimed to compare the growth and tolerance response characteristics to drought stress in several Italian ryegrass varieties cultivated in Korea. Twenty-day-old Italian ryegrass was subjected to drought treatment for 4 days, and then the growth and physiological responses of the plants were compared. Drought stress reduced leaf length, fresh weight, and dry weight in all Italian ryegrass varieties compared to the control. In addition, chlorophyll content was significantly decreased in all varieties treated with drought stress, but Fv/Fm was significantly decreased only in Winter hawk. For H2O2 and malondialdehyde (MDA) contents, Winter hawk showed the highest increase and New dawn showed the least increase. In terms of relative water content (RWC), New dawn showed the least decrease and Winter hawk showed the greatest decrease. These results indicate that New dawn is relatively drought-tolerant and Winter hawk is a drought-sensitive variety, indicating that each variety of Italian ryegrass has different drought tolerance mechanisms, which may provide basic insight for the development of tolerant varieties in the future.

Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHODS
    1. Plants growth conditions and drought treatment
    2. Measurement of relative water content
    3. Measurement of chlorophyll content and Fv/Fm
    4. H2O2 and MDA measurements
    5. Statistical analysis
Ⅲ. RESULTS AND DISCUSSION
Ⅳ. CONCLUSIONS
Ⅴ. ACKNOWLEDGMENTS
Ⅵ. REFERENCES

• Il-Kyu Yoon(Division of Applied Life Science (BK21) and Institute of Agriculture & Life Science (IALS), Gyeongsang National University, Jinju 52828, Republic of Korea)
• Min-Jun Kim(Division of Applied Life Science (BK21) and Institute of Agriculture & Life Science (IALS), Gyeongsang National University, Jinju 52828, Republic of Korea)
• Myung-Ju Kim(Division of Applied Life Science (BK21) and Institute of Agriculture & Life Science (IALS), Gyeongsang National University, Jinju 52828, Republic of Korea)
• Byung-Hyun Lee(Division of Applied Life Science (BK21) and Institute of Agriculture & Life Science (IALS), Gyeongsang National University, Jinju 52828, Republic of Korea) Corresponding author