| Broomcorn millet(Panicum miliaceum L.)is one of the most important grain and cash crops in arid and semi-arid areas,with the characteristics of short growth period,drought resistance,barren tolerance,rich nutrition and the traditional Chinese herbal drug.Head smut is the most serious disease in broomcorn millet,which threats the yield and quality.Head smut of broomcorn millet is a system infection disease that the pathogen infects the seedling,while the obvious symptoms appear in the heading stage.The symptoms appearing relatively late leading to the difficult of identification the head smut disease,which is not conductive to the further research of the disease.Research of identification technology is helpful to identify the disease in an early stage and can shorten the research cycle of the disease.The study of infection process can provide basic for the pathogenesis and resistant mechanism,therefore can play an important role in the prevention and resistant breeding.Using the method of artificial inoculation of seed saturated inoculation,this text studied the response of MDA,antioxidant protection enzymes and hormones under smut fungus stress and screened the indicators to identify the broomcorn millet head smut disease.Also the chlamydospore's germination characteristics,the infection process and anatomy structure changes were studied.The main conclusions were as follows:(1)The germination of smut fungus chlamydospore produced separate hyphae and the microspore produced by the side of mycelium.Hanging drop culture condition had a significant effect on germination of chlamydospore.The suitable of temperature were 25-30? and the proper pH were 3-7.Glucose and sucrose solution can promote the germination significantly and the suitable cultivation concentraeion were 0.5% and 0.1% respectively.The cultivation with broomcorn seeds fry sauce can obviously inhibit the germination of chlamydospore,while the 0.1% sodium chloride solution can promote the germination.(2)The result of chlamydospore germination was producing spores hyphae and the hyphae produced invaded spores in further.Then the invaded spores can produce hyphae that was capable of infection.After infecting the seedling coleoptile,the hyphae grew along the intercellular or within the cell,and then extended to the growing point of steam.At last,the pathogen completed the life cycle with the mature of broomcorn millet.With infected,the stem growing point appeared obvious symptoms.The stem edge,vascular bundle and parenchyma cells were changed as well,compared to healthy plants.(3)Compared to the healthy plants,the leaf's MDA content and SOD activity were significantly elevated;the POD activity were obviously decreased in the diseased plants.Under the stress of smut fungus,the MDA content,SOD and POD activity in the disease-resistant and susceptible materials had different changes,which can be used to identify the resistant of broomcorn to head smut disease.(4)After infection of the head smut disease,the leaf's content of IAA,GA were significantly lower and the CTK,ABA were obviously higher than that of the healthy plants.Thus the disorder of hormone metabolism had a relationship with the symptoms of the diseased plant,including the reduced plant height,the shortened intemode,the increased tillering and lobular clusters.In addition,the SA and JA content were also increased significantly after infection.The response of CTK,GA,ABA and SA content were different between disease-resistant and susceptible materials under the smut fungus stress,so they can be the indexes to identify the resistance to smut disease of broomcorn millet,and the properly sampling dates were 60-80 d,40-60 d,50-70 d,20-50 d after sowing respectively. |
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