Resistance Evaluation On Lilium Germplasins To Bulb Rot Induced By Fusarium Oxysporum

Lily bulb rot disease caused by Fusarium oxysporum is one of the most serious fungaldiseases in lily production. In this study, aseptic plantlets of twenty lily species (cultivars) werecultured on MS-FA medium and to be tested their resistance to Fusarium oxysporum. Theresults showed that there were5species with high resistant reaction,5in moderately resistant,6in moderately susceptible, and the last4in highly susceptible. In addition, the infected tissuewas observed under the microscope, and their defensive enzymes activity was investigated inorder to explore the differences of their resistance to bulb rot disease. The main conclusionswere as follows:1. Isolation and identification of pathogenic fungi(1) The strains of Fusarium oxysporum f.sp.lilii grows well on the PDA and PSA medium,it can produce a large number of small spores but does not produce sickle-type spores; But afew sickle-type spores could be produced within the tissues of lily plant.(2) There are some differences such as morphological characteristics, culture character andsporulation characteristics between different specialization types of Fusarium oxysporum; thestrains morphological characteristics will be different while culture on different culture mediumor under different culture conditions. So the composition of culture medium and the culturecondition should be remain stable during identification, and the work should be carried outunder standard conditions if conditions permit.(3) Fusarium oxysporum has many specialization types. In order to improve the accuracyand efficiency of identification, we should combine the morphological identification withmolecular identification and the isolate pathogenicity testing closely.2. Lily resistance to Fusarium oxysporum(1) The infection of Fusarium oxysporum was mainly start up begin from the wounds ofthe bulb or root, if the number of aseptic seedlings is sufficient, we should adopt the method ofwound inoculation for pathogenicity testing and variety resistance identification.(2) The toxin filtrate produced by Fusarium oxysporum f.sp.lilii can be used to identify lilyresistance to bulb rot disease. The results of toxin testing and pathogen testing are consistent.Either pathogens or its toxin liltrate can make lily disease, and the symptoms of two treatmentsare similar. In a certain range, the disease rate and disease index were positively correlated withFusaric acid (FA) concentration of the medium.(3) For those species whose survival rate of transplanting are very low, it is difficult for usto use the traditional method of field inoculation to identify their resistance to pathogen, but wecan complete the identification faster and more efficient through adding Fusarium toxins filtrateinto the culture medium.3. Study on microstructure and defensive enzymes activity of lily bulbsWhen lily infected with Fusarium oxysporum, the normal cell morphology of bulb wasdamaged, the content of store starch in parenchyma cells decreased, but the activity ofdefensive enzymes increased. Compared with susceptible germplasm, the morphology andstarch content of bulb cell of disease-resistant germplasm are less affected by pathogens.Theactivity of phenylalanine ammonia lyase and peroxidase of disease-resistant germplasm weresignificantly higher than that of susceptible germplasm.