Identification And Screening On The Resistance To Squash Blight In Seeding Stage

Squash blight is a soil-spreading disease caused by Phytophthora capisici. his one of diseases which put the most threat on the squash production. The influence of P. capisici affecting the seedling squash inoculated by the inoculating method of zoospore seedling squash inoculating, such as inoculation density, inoculating way, seedling stages and preserving moisture time was studied in this paper. The results showed:I.Inoculating density is designed 8 levels by setting up the figure and the table between the inoculating density and disease it is found that the range of comparatively suitable inoculating density is 1250-7500 spore Iml and the most appropriate density is 5000 spore/mI.2.It is found that the best seedling stage is 2 leaves comparing 4 seedling stage.3.There are 3 inoculating ways. Away them, pouring the root is the most suitable; injecting causes the disease quickly and seriously; cutting root gives the plants injury and affects the growth.4.Preserving moisture time has great influence on infection. But if the time is too short, symptom cannot been showed completely and if the time is too long, the normal growth of seedling will be affected. After inoculating, the best time to preserve moisture is 48hr; after 72hr the investigation can be designed when there is a high infecting rate and a stable symptom.5.On the basis of the above research, a test was carried on to identify the disease resistance of 29 samples and some plants with disease resistance were selected.6.By L9 (34),preserving moisture time is tested to be a key factor that affects inoculating effect and it decides the infecting degree.7.Resistance is directive relevant to POD and PPO according to the analysises of enzyme activating of squash material with different resistance; PPO in resistant material has a higher activity than infecting material after inoculating.Graduate: Zhou KeqinMajor: Vegetable breed...