Assessment strategies for screening effective bacteria as biological control agents and elucidating the mechanisms of biological control for rice blast(Magnaporthe grisea)

摘要

Rice blast disease is an important disease but effective biological control agents (BCAs)for controlling the causal organism Magnaporthe grisea, are currently unavailable.Theresearch is aiming to establish an assessment system for creening effective bacteria asbiological control agents using molecular techniques against M.grisea on rice and assess thepotential biological control agents in the greenhouse.935 bacterial isolates were obtained fromthe surface and interior of stems, phyllosphere, rhizosphere, endorhiza, and endosphere offield-grown rice plants and bulk soil and biological control potential according to in vitro andvivo activities of their extracellular metabolites (chitinase, cellulase, glucanase, protease, andsiderophores) was studied.Amplified ribosomal DNA restriction analysis and BOX-PCR
　　analysis were also performed to examine the genetic diversity of 30 isolates with at least onepoint of assessed biological control potential.The thirty isolates achieved positive biologicalcontrol efficacy ranging from 18.08％ to 77.50％ at 45 days post pathogen inoculation (dpi).Iacquired 10 well-performed potential BCAs, especially Bacillus cereus H-S in 24, Bacillussubtilis D-L in 76 displayed good biological control capacity against M.grisea diseases on rice.This demonstrated that H-S in 24 and D-L in 76 in both greenhouse and molecular techniquestests(examining of infectious growth and appressorium penetration on the rice leaf) showedhigh positive results by limiting the effects of M.grisea on the plant.Pearson correlationanalyses of assessment scores and antagonistic test in greenhouse show 0.87 and 0.73 againstM.grisea suggesting that the BCAs screening and assessing system developed is adaptable for
　　controlling rice blast disease.

目录

声明

论文说明

TABLE OF CONTENTS

ABSTRACT

LIST OF ABBREVIATIONS

PART 1：INTRODUCTION

1．1 Background

1．2 Research Content

1．2．1 Statement of the Study

1．2．2 Significant of the Study

1．2．3 Aims

1．2．4 Objectives

1．2．5 Hypothesis

1．2．6 Organization of the Research

PART 2：Literature Review

2．1 Brief History and Description

2．2 Etymology

2．3 Regional History of Rice

2．3．1 Africa

2．3．2 Asia

2．3．3 Middle East

2．3．4 Europe

2．3．5 Caribbean and Latin America

2．3．6 United States

2．3．7 Australia

2．4 Environmental Impacts

2．4．1 Rainfall and Temperature

2．4．2 Pests and Insects

2．4．3 Rice Blast Disease

2．5 Significance of Rice Blast Disease

2．6 Symptoms and Signs

2．6．1 Rice Leaves

2．6．2 Rice Collars

2．6．3 Rice Necks and Panicles

2．6．4 Rice Seeds

2．7 Pathogen Biology

2．7．1 Sexual Reproduction

2．7．2 Asexual Reproduction

2．7．3 The Infection Process

2．7．4 Disease Cycle and Epidemiology

2．8 Disease Management

2．8．1 Cultural Strategies

2．8．2 Genetic Resistance

2．8．3 Fungicide

2．8．4 Biological Control

PART 3：MATERIALS AND METHODS

3．1．Bacteria，Plants，and Their Culture

3．2．Isolation of Rice Habitat Strains

3．3 Screen for Antagonism towards M．grisea

3．4 Evaluation of Activities of Extracellular Hydrolytic Enzymes and Siderophores

3．5 Evaluation of potential biological control agents for their biocontrol ability

3．6 ARDRA and BOX-PCR Fingerprint Analysis and Identification of Bacterial Isolates

3．7 Greenhouse Test

3．8 Examination of，Conidia Germination，and Appressorium Penetration on the Rice Leaf

3．9 Statistical Analysis

PART4：RESULTS AND DISCUSSIONS

4．1 Biological Control Agents Identify

4．2 Screening Potential Biological Control Agents against M．grisea Disease

4．3 Analysis of Bacteria Activities of Extracellular Hydrolytic Enzymes and Siderophores

4．4 Bacteria Antagonists showing 4-8 Scores subjected to DNA analysis，ARDRA and BOX PCR Analysis

4．5 Biocontrol Efficacy test Against M．grisea under Greenhouse Condition

4．6 Correlation Analysis between Biocontrol Efficacy and Assessment Scores

4．7 Conidia Germination，and Appressoria on Rice Leaf Treated with(H-S in 24 and D-L in 76)

4．8 Conclusion

4．9 Future Research

REFERENCES

PAPERSPUBLISHED

APPENDIX

ACKNOWLEDGEMENTS