In Vitro Selection Of Mutants To Stem Blight Resistant And Studies On Their Resistance Mechanism In Asparagus Officinalis L

Asparagus (Asparagus officinalis L.) is recognized as the world’s high-grade nutrition and health vegetable because of its high food and medicinal value, and it is one, of the world’s top ten dishes with the laudatory title of "king of vegetables". In recent years, China has become the biggest exporter of asparagus. However, asparagus growing areas in Chian, ongoing stem blight disease often resulting asparagus field’s yields to fall seriously. Asparagus stem blight disease is caused by Phmopsis asparagi as a kind of fungal disease. Toxin is an important class of virulence factors produced by pathogen during the pathogen infecting the host. It can make the host plant show the same symptoms with bacteria. Currently, using of the toxin as a selection pressure to screen out resistance plant tissue materials in vitro has become a relatively mature and most successful system in resistance screening technique in vitro, which is an emerging field in cell engineering breeding. In this experiment, the author studied the the suitable conditions to indruce callus from asparagus stems and appropriate toxigenic culture medium and culture conditions of Phmopsis asparagi. The preparative toxin is used to induce the asparagus callus’resistance, and its impact on the activities of defense enzyme in the asparagus callus is studied. What’s more, the resistance of the plantlets induced from resistance callus are tested and evaluated. And established the in vitro screening system of asparagus stem blight resistant mutants. The main results were as follows:1. The most suitable conditions of’Apollo’、’Champion’and’NJ987’stem callus’ induction is MS+1.5mg/L 6-BA+1.5～2.0mg/L NAAo2. Phmopsis asparagi were separated from the diseased plants by conventional separation and gradient dilution methods. It was found that the optimum toxigenic culture conditions is in Fries medium whose PH was 7, culture environment temperature was 27℃, continuous shaking in the rotate speed of 120rpm for 12 days in dark. Toxin production under these conditions hsd the strongest inhibition effect on asparagus radicle, the highest inhibition rate was 97.69%. And through inoculation toxin on asparagus in field, proved the toxin producted by Phmopsis asparagi had pathogenicity to asparagus.3. Toxin induced’Apollo’,’Champion’and’NJ987’callus’resistance enhanced. Toxin concentration for resistant callus selection was 30%-40%.4. After toxin treatment, activity of SOD, POD, CAT, PAL PPO in callus showed a trend of decline after rising first, and were always higher than the corresponding control, but the rising degree and the peak time were different of this 5 kinds of enzyme. This showered that toxin stress could induce disease resistance of asparagus callus,5 kinds of enzyme coordinated collaborative could improve the asparagus callus’resistance to the stem blight pathogen toxin.5. By resistance identification test,3 variety mutation seedling in vitro, induced from the screening callus before, onset of stem blight were later than the control, and the disease severity was also significantly lower than the control within a certain time, showing the variety mutation had resistance to Phomopsis asparagi.