Influence On The Fusarium Wilt Of Root Exudates From Different Cucumber Disease-resistant Varieties And Primary Studies On The Mechanism Of The Influence

Influence on the Fusarium wilt of different root exudates were studied. The results showed the plants treated with root exudates from JY4-RE became diseased after inoculated for 4 days. And the infection rate of plants treated with JY4-RE and BSS-RE were 18.5% and 10.0% compared to 2.5% of JCh4-RE and 1.0% of CK after inoculation for 10 days. To the 15th days the infection rate of plants treated with JY4-RE (34.5%) and JCh4-RE were significantly higher and lower than CK. And the infection rate of treatments of JY4-RE and CK were nearly of the same:41%, compared to 24.0% of JCh4-RE. All the results indicated that root exudates from resistant varieties might inhibite the occurrence of Fusarium wilt, which was promoted by root exudates from susceptible varieties.Plant height,fresh weight,root system activity and conductance(severity of damage) of Jinyan-4 cucumber seedlings were determinated. The following were the results: plants treated without root exudates were the highest, and plants treated with JY4-RE were the the lowest and lightest; while influence on plants treated with JCh4-RE and BSS-RE was not obvious. That showed root exudates from susceptible varieties might significantly inhibite plant height and fresh weight of Jinyan-4 cucumber seedlings. The active area of root system of plants treated with JY4-RE were the lowest; and in early stage the active area of root system of plants treated with JCh4-RE were higher, while CK were higher in late stages. The severity of damage of plants treated with JCh4-RE were the lowest, contravily, those of plants treated with JY4-RE were higher than others. Besides, JY4-RE might promoted the growth of Fusarium wilt, which was inhibited by JCh4-RE and BSS-RE. Jinyan-4 cucumber seedlings were inoculated with Fusarium wilt of cucumber after watered with asepsis water and JY4-RE,JCh4-RE and BSS-RE for some days, and some changes of root system of cucumber seedlings, including root system activity,severity,contents of soluble sugar and lignin,activities of POD,PPO,PAL and SOD, before and after inoculated, were determined. Then the mechanisms of the effects of root exudates on the resistance to the Fusarium wilt of cucumber were studied. The following are the results:The active area of root system of the treatments watered with JY4-RE were lower than others before and after inoculated, while the severity of damage were higher than others ; The contents of soluble sugar of treatments watered with JCh4-RE and BSS-RE were higher than others before inoculated, but in the 10 days after inoculation the contents of CK was higher than other treatments;The contents of lignin of CK, which reached 2.9 times of before inoculation, were obviously higher than others before and in the 4 days after inoculation;The PPO and POD activity of treatments of JCh4-RE arose obviously, and peak activity were higher than others;The PAL activity of CK was higher than other treatments, and a very significant peak activity appeared between 48 and 60 hours after inoculation;After 12 hours a little peak activity appeared in CK and treatment of JCh4-RE after inoculation, while in treatment of JY4-RE the peak activity appeared after 24 hours, and later the SOD activity of CK and treatment of JY4-RE were higher than others.