Research On The Relationship Between The Resistance To Tomato Bacterial Wilt And Enzyme Activities

Tomato bacterial wilt caused by Ralstonia solanacearum is a devastating disease.It has occurred in various parts of the world,especially in tropical and subtropical regions.It is a kind of soil-borne disease and has a wide range of hosts. At present,the tomato bacterial wilt happens in an increasing frequence,which results in a decreasing production and total destruction in a large area of tomatoes. Tomato bacterial wilt has become a major obstacle in tomato cultivation.However, researches on the physiological and biochemical mechanisms of resistance to tomato bacterial wilt are very few,and it is very difficult to collect anti-bacterial wilt tomato materials.These problems cause many difficulties in breeding anti-bacterial wilt tomatoes.Most of traditional identification methods are nursery and field surveys. They are very time-consuming and have heavy workload.After the 1980s, enzymatic methods and molecular marker-assisted breeding are widely used and could reduce the resistance breeding process greatly.In this paper,the changes of enzyme activity and isoenzyme were studied after inoculating with Ralstonia solanacearum,so that the levels of resistance to bacterial wilt could be forecasted.As a result,breeding work could be carried out selectively and work efficiency could also be improved.At the same time,this research could promote the study on other physiological and biochemical indicators about the resistance to tomato bacterial wilt.In this paper,the seedling and adult resistance identifications of five tomato cultivars to bacterial wilt were studied.Meantime,the activity changes of five enzymes and changes of two isoenzymes were studied.The results were as followings:Through the routine inoculation assay,the strain of Ralstonia solanacearum extracted from the diseased tomato plant in the experimental field of horticulture department in sichuan agricultural university had pathogenicity.The tomato seedlings were inoculated by cutting the roots and pouring.The best concentration of the bacteria used to inculate the tamato was 3×10~8 CFU/ml.The disease rates were investigated at the seven day,the fourteen day,and the twenty-first day after the inoculation.The results showed that the disease rates of S13,S24,L33,L55 were significantly lower than that of Qiangfeng.From the results of the three investi-gations above-mentioned,the five kinds of tomato could be divided into three types:S13,S24,L33 were moderate resistance varieties;L55 was a disease tolerant variety;Qiangfeng was a disease susceptible variety.The tomato adults were inoculated by cutting the roots and pouring.The concentration of the bacteria used to inculate the tamato was 6×10~8 CFU/ml.The results showed that the resistance indexes of the four tomatoes were 8.6,8.3,9.5, 6.8.All of the resistance indexes were bewteen the range of 5-9.9,so they were moderate resistance varieties.However,the resistance indexe of Qiangfeng was only 2.8,so it was a disease susceptible variety.The activities of five defense enzymes in the tomato leaves without inoculating with Ralstonia solanacearum were in dynamic equilibrium.After inoculation,the four enzymes'(PAL,PPO,POD,SOD) activities of all varieties were increasing.The enzyme activities of S13,S24,L33,L55 were always higher than those of the enzyme activities before the inoculation,and the ascending speed,the largest increasing rate, the peak values of the four cultivars were higher than those of Qiangfeng.The enzyme activities of Qiangfeng in early days after inoculation was higher than that of the enzyme activitie before inoculation,while was lower than those of that of the enzyme activitie before inoculation in late days after inoculation.The changes of enzyme activities of CAT in leaves of all cultivars were turbulent and were absence of orderliness after inoculation.The enzyme activity peak values of the PAL,PPO, POD,SOD in the four tomato materials except Qiangfeng were negatively correlated with seedling infection,and were positively correlated with adult resistance.So,the four enzymes(POD,PPO,PAL,SOD) of tomato leaves could be used as assistant guidelines of selecting the resistance cultivars in early phase after inoculation with R.solanacearum,while CAT needed more studies.There were no apparent changes at isozyme spectra numbers of POD and PPO in leaves of S13,S24,L33,L55 after inoculation with Ralstonia solanacearum,but the intensities of the isozyme spectra were significantly enhanced.However,the intensity of the isozyme spectra of Qiangfeng had no apparent change.