| Stem canker(black scurf disease) caused by Rhizoctonia solani(R.solani) has become one of the main soil-born diseases which limits the development of potato industry in Gansu province’s. For effective prevention and control of potato stem canker, we throughed the method of in vitro experiment, used the method of plant histology observing the infection process. For studying the disease process and pathogenic mechanism, throughed the method of soil cultureⅠandⅡ,combine with the determination of physiological and biochemical indexes, researched the infection process, disease progress, and pathogenic mechanism of potato Rhizoctonia solani,Test process is as follows:CK-1: control potato(the same part of T1-1)CK-2: control potato(the same part of T1-2)T1-1: disaese organization of treatment potatoT1-2: health organization of treatment potatoMain results are as follows:1. In vitro culture experiment of potato base stem showed that: hyphae started to attach to the surface of host in 12 h, appressorium formed in 36 h, infection cushion formed in 48 h.2. Soil culture experiment Ⅰshowed that: the infection order is bud, stem, root, stolon and tuber.Infection of Rhizoctonia solani to potato bud and bud tissue damage is the main reason why the plants had weaker growth: after infecting 7d, can observe canker near bud eye, the primary bud germination is restrained, leading to secondary bud growth, after infecting 10d-14 d, can observe canker in primary bud which have germinated, bud germination is restrained, leading to growth stage of potato delayed and growth potential weaken.Rhizoctonia solani had a significant effect on potato base stem organization morphological structure and defense enzyme activity. After infecting 35 d,can observe canker in potato base stem. Deformation and fracture of cell wall, damage of cell membrane, structural deformation plastid cytoplasm dissolution and plasmolysis deformation and fracture, cell membrane damage, structural deformation of plastid structure, dissolution of cytoplasm and plasmolysis can be observed under electron microscope.The activity of Acid phosphatase(ACP) go up after infection. Activity of ACP for diseased part of treatment plant(T1-D) is 2.24 times than healthy part(T1-H), and is 2.56 times than control part(CK).3. Soil culture experiment Ⅱshowed that: After infecting 25 d, the activity of Peroxidase(POD)、Catalase(CAT) and the content of Malondialdehyde(MDA) in diseased part of treatment plant(T1-1) are higher than control plant(CK-1), activity of Superoxidase Dismutase(SOD) is higher than CK-1 24.1% and152.6% respectively after infecting 30 d and 35 d. the activity of CAT is higher than CK-1577.8%、233.6% and 277.8% after nfecting25 d, 30 d and 35 d. the activity of POD is higher than CK-17.2%、4.3% and 16.3%. The content of MDA is higher than CK 89.4%, 68.9% and 70.2%.For the result of healthy part in treatment potato(T1-2): defense enzyme compare with control potato(CK-2) have significant difference after infecting 35 d,The activity of SOD is higher than CK-2 132.5%, the activity of POD is higher than CK-2 48.3%, the activity of CAT is higher than CK-2 226.5%、103.2% and145.3% after infecting 25 d,30d and 35 d respectively.The content of MDA have no difference with CK-2 in three time.The activity of SOD,CAT and the content of MDA in diseased part of treatment plant(T1-1) is higher than healthy part in treatment potato(T1-2), The activity of SOD in T1-1 is higher than T1-2 27.6%、40.4% and 29%, the activity of CAT in T1-1 is higher than T1-2 129.9%、116.5% and 146.4%. The content of MDA in T1-1 is higher than T1-2 93.8%、223.3% and 195.6%. The activity of POD is higher than T1-2 75.9% after infecting 30 d.It shows that after the pathogen infect can induce the defense responses of host plant4. Rhizoctonia solani influence the groeth of potato.Plant height,stem diameter and fresh weight in treatment plant(T1)are all significantly lower than control group(CK). Compare with CK,T1 plant height in seedling stage and tuber bulking stage is decreased 15.4% and 22.9% respectively. Stem diameter is decreased 8.8% and 10.7% respectively. 7 times sampling from seedling stage to tuber bulking stage,fresh weight in T1 is significantly lower than CK in 90 d growth period, and the reduce degree of plant fresh weight is bigger than fresh weight of root.To sum up, After infection Rhizoctonia solani can inhibit potato seed germinating, destroy organization structure, result in growth potential weakened, growth stages later, defensive enzymes activities and malondialdehyde content both go up. |
PDF Full Text Request