研究主題 Research Topics

Powdery mildew (PM) is a common foliar disease of soybean. In the trails of soybean-rice rotation in the spring-fall growing season, soybean PM occurs more frequently in the spring of Taoyuan county. While fungicide application can reduce PM incidence, studying soybean PM resistance would benefit resistance breeding and reduce the dependence on fungicides. M.S. student Cheng-Chun Huang applied bulk segregant RNA-Seq (BSR-Seq) to uncover the genetic makeup of PM resistance in the 'Kaohsiung 11 (KS11)' variety of Taiwan. The mapping results not only identified the Rmd1 locus decribed in literature, but also a MLO gene in the Rmd1 locus of 'KS11'. The MLO gene expression was lower in the resistant parent 'KS11' and the bulked progenies, indicating the possibility of this MLO gene contributing PM resistance. The study has been published in the BMC Plant Biology journal. link 

Soybean chitinases belong to one of the pathogenesis-related proteins (PR-proteins). In facing Fusarium oxysporum infection, soybean chitinase gene expressions were up-regulated to enhance defense responses. Soybean chitinase genes can also be up-regulated encountering beneficial rhizobacteria. M.S. student Jheng-Yan Chen focused on 3 phylohenetic-closed soybean chitinases (GmChi01, GmChi02, GmChi16) and found that over-expression of GmChi02 and GmChi16 in transgenic Arabidopsis lines reduced disease severity, while GmChi01 provided no protection. However, only GmChi02 was inducible by F. oxysporum and rhizobacteria, indictaing the regulation on soybean chitinase gene expressions may have selective preference. In transcriptomic analyses of 6 rhizobacteria from different genera, the results found that different rhzobacteria indeed induced different soybean chitinase genes. For chitinase genes responded to rhizobacteria, promoter sequence analysis identified conserved motifs, indicating the likelihood of co-evolution between rhizobacteria and inducible soybean chitinase genes. The results have been published in the Frontiers in Plant Science journal. link

Red crown rot has become an emerging problem for soybean and edamame production in the Kaohsiung-Pingtung region of Taiwan since 2018, and it has been recognized as a recent threat for soybean production worldwide. Currently, there is no resistant soybean variety available for controlling red crow rot; therefore, fungicide screening is the primary and urgent need to develop a disease management strategy. Ph.D. student Ping-Hu Wu established a microplate-based high-throughput screening platform, which incorporated with the Z' factor and surface scanning method to reduce the high false-positives associated with high throughput manipulation. In addition, the growth curve, conidia concentration, and absorbance wavelengths were optimized to identify several effective fungicides. Among these fungicides, seed treatment with cyprodinil + fludioxonil showed the best protection. In assessing 80 field isolates of the casual fungus Calonectria ilicicola, there was no field-developed resistance for cyprodinil + fludioxonil. Collectively, cyprodinil + fludioxonil can be recommended as the fungicide to control red crown rot. The detail results have been published in Plant Disease, a jounral of American Phytopathological Society (APS). link

Athelia rolfsii is one of the earliest fungi used to study the development of sclerotia formation, including the identification of reactive oxygen species (ROS) on stimulating sclerotia formation. However, the gene expressions of sclerotia formation remained unexplored for A. rolfsii. M.S. student Kuan-Yu Pan applied RNA-Seq on A. rolfsii sclerotia to profile the transcriptomes of four development stages. The results found the ROS-related genes were mostly up-regulated in the later stages, and among culture assays amended with several antioxidants or oxidants, glutathione was the only one reduced the sclerotia number. Considering glutathione also causes influx of Ca2+, culture assay with supplement of Ca2+ indeed reduced the sclerotia number. Compare to the results of Macrophomina phaseolina and Sclerotinia sclerotiorum that both ROS and Ca2+ crosstalks to regulate the sclerotia formation, Athelia rolfsii appears to be only regulated by Ca2+. The discoveries have been published in the MIcrobiology Spectrum, a jounral of American Society for Microbiology (ASM). link

Rhizoctonia solani is one of the major pathogens causing soybean seedling diseases, and M.S. student Yu-Cheng Lin identified the major anastomosis group (AG) of R. solani in the Kaohsiung-Pingtung region of Taiwan belongs to AG-7. Yu-Cheng utilized the Oxford Nanopore Technologies and Illumina RNA-Seq to sequence and assemble the first R. solani AG-7 genome, and applied genotyping-by-sequencing (GBS) to obtain single nucleotide polymorphisms (SNPs) of 154 R. solani AG-7 field isolates. The results of genome-wide association study (GWAS) further revealed for the first time that sclerotia-forming capability was governed by both genetic hertability and environmental effects. The study has been published in the Microbial Genomics, a  journal of the Microbiology Society. link

Macrophomina phaseolina produces microsclerotia to survive unfavorable environments and serve as primary inoculum in fields. Many literature described the sclerotia or microsclerotia formation of Sordariomycetes being stimulated by reactive oxygen species (ROS), but it remains unclear if M. phaseolina, which belongs to the Dothideomycetes, is still being regulated by ROS for microsclerotia formation. M.S. student Hsien-Hao Liu applied RNA-Seq on 4 stages of microsclerotia development, and identified significant difference on gene expressions and functional enrichments. The results from culture assays with antioxidants or oxidants found that O2- instead of H2O2 is the major ROS stimulator to initiate microsclerotia formation of M. phaseolina. The study has been published in the MIcrobiology Spectrum, a jounral of American Society for Microbiology (ASM). link