Effects of Combination of Straw Returning and a Microbial Agent on Microorganisms and Enzyme Activity in Rhizosphere Soil and Yield of Late Rice

By using red soil and late rice Wufengyou T025 as the tested materials,the influences of straw returning with a microbial agent on the quantity of microorganisms and enzyme activity in rhizosphere soil in fields were studied,and soil productivity was tested with yield and agricultural traits of late rice. The results showed that straw returning with the microbial agent could significantly improve the quantity of bacteria,fungi and actinomyces in soil,enhance the activity of sucrase,urease,catalase and cellulase,and improve the number of grains per spike,setting percentage,thousand seed weight and yield of late rice. The combination of rice straw returning and the microbial agent has a good prospect of application.

Evaluation of 0.3% Agricultural Antibiotic 702 AS against Three Pathogenic Fungi of Rice

Abstractsolution （AS） against Rhizocto- nia solani, Magnaporthe grisea and Ustilaginoidea virens. [ Method] The toxicity effect of 0.3% agricultural antibiotic 702 AS against R., solani, M. grisea and U. virens were studied by mycelial growth rate method and mycelial wet weight method. [ Result ] The EC50 and EC50 values of agricultural antibiotics 702 AS to R. solani, M. grisea and U. virens in vitro condition were 4.16 and 16.17 mg/L, 16.05 and 41.85 mg/L, 111.2 and 389.0 mg/L, respectively. Agricultural antibi- otics 702 AS had good inhibition effect against R. solani and M. grisea and could basically achieve the effects of commercially available Jinggangmycin and kaanga- mycin, but the inhibition effect against U. v/rens was relatively weak. The preventive activity of aqueous solution was obviously higher than treatment activity. [Conclusion] 0.3% Agricultural antibiotic 702 AS is considered to be a potential biological control agent against R. solani, M. grisea and U. virens, and can be used as the potential alternative pesticide of Jinggangmycin.

Field Efficacy of Agricultural Antibiotic 702 against Rice Leaf Blast and Panicle Blast

The control effects of agricultural antibiotic 702 （ ag-antibiotic 702） on rice leaf blast and panicle blast were evaluated in field trials. With ag-antibiotic 702 and the two-line early hybrid rice 287 as test materials, different concentrations of ag-antibiotic 702 liquids were sprayed at tiUering stage and full heading stage of rice. In leaf blast test, the disease indexes of leaf blast at tillering stage were surveyed at 1 d prior to the first spraying and at 15 d post spraying, respectively. The disease indexes （DI） and the rice yield in panicle blast test was investigated at milky stage. Meanwhile, enzyme activities, including peroxidase （ POD）, catalase （CAT）, superoxide dismutase （SOD）, phenylalanine ammonia-lyase （PAL）, and polyphanol oxidase （PPO）, were measured. Kasugamycin （45 μg/mL） and deionized water were designed as positive and negative controls. When the concentrations of ag-antibiotie 702 were 15, 30 and 45 μg/mL, the control effects against leaf blast were 72.14%, 80.32% and 85.22%, respectively; the control effects on panicle blast were 74.08%, 84.87% and 86.58%, respectively; and the yield increase rates were 17.28%, 21.40% and 22.57%, respectively. So, ag-antibiotic 702, as a new agricultural antibiotic fungicide, could effectively cantrel rice blast by inducing defensive enzymes, and increase rice yield. The results will contribute to further development of ag-antibiotic 702 and its application in rice blast control.

不同提取剂提取土壤中重金属能力的对比研究

为比较不同浸提剂的提取能力,采用去离子水(DI)、硫酸-硝酸(AA)、二乙烯三胺五乙酸(DTPA)、醋酸缓冲溶液(TCLP)、氯化钙溶液(CC)对Cu、Ni、Pb、Cd复合污染土壤中的有效态重金属进行提取,同时采用欧共体标准物质局提出的BCR连续提取法(BCR)和TESSIER提出的SEP连续提取法(Sequential Extraction Procedures)对污染土壤中的重金属进行形态分析,探究了不同多级提取法中重金属形态分布的关系以及浸提剂浸出的重金属质量分数与多级提取法中重金属形态分布的关系.研究结果表明:各浸提剂的浸提能力从强到弱依次是:DTPA、TCLP、CC、AA、DI;对于Cu和Ni元素,BCR法提取的活跃形态的质量分数与SEP法提取的活跃形态的质量分数相近;TCLP浸出重金属的质量分数与BCR连续提取法中重金属的形态存在紧密联系,TCLP浸提剂能提取出弱酸可提取态的重金属;DTPA浸出重金属的质量分数与SEP连续提取法中重金属的形态也存在紧密联系,DTPA浸提剂能提取出可交换态、碳酸盐结合态和铁锰氧化态的重金属.本研究结果可为重金属污染土壤修复评估标准提供参考依据.

Changes in Antioxidant Enzyme Activities and Malondialdehyde(MDA) Content of Rice with Blast Resistance Induced by Ag-antibiotic 702

The paper was to explore the effect of rice blast resistance induced by Ag-antibiotic 702 on antioxidant enzyme activities and malondialdehyde（ MDA）content. At three-leaf and one-heart stage of Luliangyou 996,15 μg/mL Ag-antibiotic 702 was sprayed,while Validamycin and distilled water were sprayed as positive control and negative control,respectively. The antioxidant enzyme（ SOD,POD,PPO,CAT and PAL） activities and malondialdehyde（ MDA） content in rice leaves were determined every 24 h within 168 h post spraying. Compared with CK,the MDA content and activities of the five antioxidant enzymes increased in Agantibiotic 702 treatment,Validamycin treatment and M. grisea inoculation treatment. The MDA content and SOD,CAT and POD activities in Ag-antibiotic 702 treatment were significantly higher than those in M. grisea inoculation treatment in early stage,and the APX and LOX activities increased more remarkably and rapidly. The induction effect of Ag-antibiotic 702 could reach or exceed that of Validamycin treatment. Ag-antibiotic 702 enhanced the resistance to rice blast because MDA content and antioxidant enzymes activities were improved in rice leaves. Therefore,the increase of rice blast resistance induced by Ag-antibiotic 702 in rice was positively correlated with the increase of MDA content and antioxidant enzymes activities in rice leaves.

Changes in Protein Content and Chitinase and β-1,3- glucanase Activities of Rice with Blast Resistance Induced by Ag-antibiotic 702

[Objective] The paper was to explore the effect of rice blast resistance induced by Ag-antibiotics 702 on protein content and chitlnase and β-1,3-glucanase activities in rice. [ Method] At the fourth leaf stage of Luliangyou 996, 15 μg/mL Ag-antibiotic 702 was sprayed, while Validamycin and distilled wa- ter were sprayed as positive control and negative control, respectively. All treatments were inoculated with spore fluid of Magnaporthe grisea at 48 h post spraying, and the rice inoculated with only distilled water was used as blank control. The enzymes activities （endochitinase, exochitinase and β-1,3-glucanase） and total pro- tein content in rice leaves were determined every 24 h within 168 h post spraying. [ Result] Compared with the blank control, the rice inoculated with spore fluid of M. grisea could significantly increase the total protein content and the activities of β-1,3-glucanase and chitinase. The induction effect of Ag-antibiotics 702 exceeded that of Validamycin treatment. And the changes in activities of β-1,3-glucanase and chitinase had obvious synchronicity. [ Conclusion] Ag-antibiotic 702 can significantly improve the total protein content and the activities of β-1,3-glucanase and chitinase, thus enhancing the resistance to rice blast.

Blast Resistance of Rice Induced by Ag-antibiotic 702

To explore rice blast resistance induced by Ag-antibiotic 702, different concentrations of Ag-antibiotic 702 were spayed on susceptible variety Luliangyou 996 at three-leaf and one-heart stage, to screen the optimal concentration for inducing rice blast resistance. Ag-antibiotic 702 was sprayed at seven different growth stages of rice, to determine the best growth stage for induced blast resistance and duration of blast resistance. Various treatments were inoculated with spore fluid of Magnaporthe grisea at 4 d post spraying, and disease index and incidence rate as well as induction effect of different treatments were investigated after 7 d. The results showed that six concentrations of Ag-antibiotic 702 could induce rice resistance against blast, and 15 μg/mL led to the highest blast resistance; spraying 15 μg/mL Ag-antibiotic 702 at seven different growth stages could induce rice resistance against blast ; the three-leaf and one-heart stage was the best growth stage for inducing rice blast resistance, and the relative induction effect reached 56.56% ; rice blast resistance was the highest at 48 -96 h post spraying, and duration of induced rice blast resistance exceeded 144 h. The study will provide useful experimental data for further development of Ag-antibiotic 702 and application of pre- vention and control methods against rice blast.

Inhibition Mechanism of Antifungal Monomer DZP8 against Rhizoctonia solani

In order to study the inhibition mechanism of antifungal monomers DZP8 produced by streptomyces 702 strain against Rhizoctonia solani, the effects of DZP8 on mycelial morphology were investigated under light microscope, and the effects of DZP8 on mycelial inclusion leakage and cell membrane damage of myceli-um were determined. The results showed that DZP8 caused a series of changes in mycelial morphology of R. solani in liquid culture condition. DZP8 treatments with concentrations of 1.81 and 3.35 μg/mL for 24 h caused big vacuole, rough surface and more inclusions of mycelium. With the treatment time prolonging, the mycelium distorted and appeared irregular constriction. DZP8 treatment with concentration of 20.10 μg/mL led to the increase of conductivity of mycelium culture liquid, leakage of soluble sugar and protein, and the lipid peroxidation of mycelium membrane. It was found that DZP8 at a very low concentration could cause changes of mycelial morphology of R. solani, while only a certain concentration could cause significant damage to cell membrane. This indicated that cell membrane might be one of the action sites of DZP8, and it might have other action sites or mechanism.