Studies On Disease Resistance Mechanism Of Capsicum Wilt

In this paper, biological characters of Fusarium oxysporum vasinfectum of capsicum wilt was tested and the resistance of different capsicum cultivars was identified. The activites of polyphenol oxidase(PPO) ascorbate oxidase( OAA) , vitamin C MDA sugar and water-soluble protein content in seedlings inoculated with Fusarium oxysporum were measured. Meanwhile the sections of different positions of infected plants were observed by means of optical microscope. The results were showed as follows:1. The tests of biological characters of Fusarium oxysporum vasinfectum showed the range of temperature for hyphae growth was 5-38#, with an optimum of 25-30#. The range of pH for hyphae growth was 4-11. while the optimum was 6-7. The optimum temperature for germination was 25-30#. The range of pH for germination was 3-11, with an optimum of 5-7. The lethal temperature of conidia was 50# for 10 minutes. The optimum carbon sources were lactose, sucrose and maltose and the optimum nitrogen source was asparagine.2. Through identifying of disease resistance to 16 capsicum cultivars, it is found that Tedaniujiaojiao is a resistant variety, while Houpiqiemen is a susceptible variety.3. No matter in root or leaf, PPO in resistant variety treated with Fusarium oxysporum was higher than control, while PPO in susceptible variety was lower than control. After inoculation, the content of PPO in resistant variety was evidently higher than susceptible variety. Changes of the activities of AAO was the same as PPO. So, PPO and AAO content have close correlation with the resistance of capsicum wilt.4. Vc was likely to react on disease resistance.5. Susceptible variety, compared with resistant variety, display much greater increasing rate of MDA content in treatment than in control.6. Sugar content in susceptible variety was higher than resistant variety in root or leaf before inoculation or after inoculation. Sugar in resistant variety treated with Fusarium oxysporum was higher than control, but susceptible variety was contrary.7. Dynamic changes of protein content had great differentiation between resistant variety and susceptible variety. After inoculation, protein content of resistant variety increased, while susceptible variety decreased.8. Results of paraffin wax slice showed: Hypha didn't exist in each section of O degree infected plants and the vessels of these plants were normal. Hypha only existed in root vessels of I and II degree infected plants and lots of wall-coatings tyloses were formed in these vessels. In root and caudex vessels of III degree infected plants , there were much hypha and little tyloses.