US National Arboretum

 


Floral and Nursery Plants Research Unit

Dr. Dilip K. Lakshman

Research Plant Pathologist
{Beltsville, MD}

Dilip.Lakshman@ars.usda.gov

PROJECT PLAN TITLE:  
Biologically based management strategies for control of soil-borne pathogens of ornamental and vegetable crops as an alternative to methyl bromide pre-plant soil fumigation.

INTRODUCTION:  
Conducts research on important soil-borne fungal and bacterial pathogens of ornamental and vegetable plants, including Rhizoctonia solani. Current research interests include:

Elucidation of fungal genes and metabolic processes affecting virulence.

Molecular identification of soilborne plant pathogens.

Characterization of fungal double-stranded RNAs (dsRNAs) mediating virulence and hypovirulence.

Transformation of fungi to understand pathogenesis and mechanism of biocontrol.

Exploration and development of biorationals and biocontrol agents for plant disease suppression.

Development of transgenic resistance against plant pathogens.

PROGRESS:  
Evaluated botanical formulations as effective antibacterial agents to control soilborne bacterial and fungal plant pathogens.

Developed a method of studying proteomics of an important soilborne fungal plant pathogen Rhizoctonia solani AG-4 to investigate its biology and pathology and identified several pathogenicity-associate R. solani genes through Expressed Sequence Tag (EST) analysis.

Developed an efficient Agrobacterium-mediated protocol for molecular transformation of the gladiolus wilt causing pathogen Fusarium oxysporum fsp. gladioli with green, yellow and cyan fluorescent genes. 

Demonstrated that the transgenic expression of an antimicrobial milk protein lactoferrin in plants imparts resistance to R. solani and Fusarium graminearum

PLANS:   
Investigate virulence mechanism of R. solani using transcriptomic, proteomics and metabolomic approaches.

Characterize and use hypovirulent isolates and biocontrol agents for the control of soil-borne pathogens on ornamental and vegetable crops.

Explore and develop organic amendments and biorationals for the management of soil-borne pathogens inducing damping-off and stem rot diseases in ornamentals and vegetables.

Investigate the effectiveness of microbial antagonists in combination with reduced risk pesticides in the management of soil-borne fungal pathogens.

PEER-REVIEWED JOURNAL ARTICLES:

2012. Lakshman, D. K., Alkharouf, N., Roberts, D.P., Mitra, A., and Natarajan, S. S.  Gene expression profiling of the plant pathogenic basidiomycetous fungus Rhizoctonia solani AG 4 reveals putative virulence factors. Mycologia, (In Press).

2012. Kong, H.S., Roberts, D.P., Patterson, C.D., Kuehne, S.A., Heeb, S., Lakshman, D.K., and Lydon, J.  Effect of Overexpressing rsmA from Pseudomonas aeruginosa on Virulence of Select Phytotoxin-Producing Strains of P. syringae. Phytopathology 102(6): 575-587. 2012. (cover page article).

2012. Han, J., Lakshman, D.K., Galvez, L.C., Mitra S., Baenziger P.S., and Mitra, A.  Transgenic expression of lactoferrin imparts enhanced resistance to head blight of wheat caused by Fusarium graminearum. BMC Plant Biology. 12: 33 Online, DOI:10.1186/1471-2229-12-33. URL: http://www.biomedcentral.com/content/pdf/1471-2229-12-33.pdf.

2012. Lakshman, D.K., Pandey, R., Kamo, K., Bauchan, G., and Mitra, A.  Genetic transformation of Fusarium oxysporum f.sp. gladioli with Agrobacterium to study pathogenesis in Gladiolus. European J. of Phytopathology. Online, pp. 1-10, DOI 10.1007/s10658-012-9953-0.

2011. Roberts, D.P., Lohrke, S.M., McKenna, L.F., Lakshman, D.K., Kong, H., Lydon, J.  Mutation of a degS Homologue in Enterobacter cloacae Decreases Colonization and Biological Control of Damping-Off on Cucumber. Phytopathology101(2): 271-280.

2012. Natarajan, S.S., Xu, C., Garrett, W.M., Lakshman, D.K., and Bae, H. Assessment of the natural variation of low abundant metabolic proteins in soybean seeds using proteomics. J. Plant Biochem. Biotechnol. 21: 30-37.

2011. Nguyen, T.C., Lakshman, D.K., Han, J., Galvez, L.C., and Mitra, A.  Transgenic Plants Expressing Antimicrobial Lactoferrin Protein are Resistant to a Fungal Pathogen. J Plant Mol Biol Biotechnol 2: 1-8. 

2011. Dhar, A.K., Kaizer, K.N., Betz, Y.M., Harvey, T.N., Lakshman, D.K.  Identification of the core sequence elements in Penaeus stylirostris densovirus promoters. Virus Genes. 43: 367–375. 

2010. Huang, Q. and Lakshman, D.K. Effect of clove oil on plant pathogenic bacteria and bacterial wilt of tomato and geranium. Journal of Plant Pathology 92: 701-707. 

2010. Dhar, A.K., Lakshman, D.K., Amundsen, K., Robles-Sikisaka, R., Kaizer, K., Roy, S., Hasson, K.W., and Allnutt, F.C.T.  Characterization of a Taura syndrome virus isolate originating from the 2004 Texas epizootic in cultured shrimp. Arch Virol. 155: 315-327. 

2010. Dhar, A.K., Kaizer, K., and Lakshman, D.K.  Transcriptional analysis of Penaeus stylirostris densovirus genes. Virology 402: 112-120. 

2008. Lakshman D.K., Natarajan, S.S., Garrett, W., Lakshman, S., and Dhar, A.K.  Optimized protein extraction methods for proteomic analysis of Rhizoctonia solani. Mycologia, 100: 867-875.

2008. Chung, S., Kong, H., Buyer, J.S., Lakshman, D.K., Lydon, J., Kim, S. and Roberts, D.P.  Isolation and partial characterization of Bacillus subtilis ME488 for suppression of soilborne pathogens of cucumber and pepper. Appl Microbiol Biotechnol 80: 115–123.

2008. Meyer,S.L.F,  Lakshman, D.K.,  Zasada, I. A.,  Vinyard, B.T., and  Chitwood, D.J.  Phytotoxicity to Vegetable Crop Seedlings and Suppression of Root-knot Nematode with Clove Oil Application. HortTechnology 18: 631-638.

2008. Meyer, S., Lakshman, D.K., Zasada, I., Vinyard, B., and Chitwood, D.  Dose-response effects of clove oil from Syzygium aromaticum on the root-knot nematode Meloidogyne incognita. Pest Management Science 64: 223–229.

2007. Roberts, D.P., McKenna, L.F., Lakshman, D.K., Meyer, S.L.F., Kong, H., de Souza, J.T., Lydon, J., Baker, C.J., Buyer, J.S., and Chung. S.  Suppression of damping-off of cucumber caused by Pythium ultimum with live cells and extracts of Serratia marcescens N4-5. Soil Biology and Biochemistry 39: 2275-2288.

2007. Dhar, A.K., Lakshman, D.K., Natarajan, Allnutt, F.C.T., and van Beek, N.A.M.  Functional characterization of putative promoter elements from infectious hypodermal and hematopoietic necrosis virus (IHHNV) in shrimp and in insect and fish cell lines. Virus Research 127: 1-8.

2006. Meyer, S.L.F., Zasada, I. A., Roberts, D.P., Vinyard, B.T., Lakshman, D.K., Lee, J.K., Chitwood, D.J., and Carta, L.K.  Plantago lanceolata and Plantago rugelii extracts are toxic to Meloidogyne incognita but not to beneficial plant-pathogenic microbes. Journal of Nematology 38: 333-338.

2006. Lakshman, D.K., Liu, C., Mishra, P.K., and Tavantzis, S.M.  Characterization of the arom gene in Rhizoctonia solani, and transcription patterns under stable and induced hypovirulence conditions. Current Genetics 49: 166-177.

2003. Liu C., Lakshman, D.K. and Tavantzis S.M.  Expression of a hypovirulence-causing double-stranded RNA is associated with up-regulation of quinic acid pathway and down-regulation of shikimic acid pathway in Rhizoctonia solani. Current Genetics 42: 284-291. 

2003. Liu C., Lakshman, D.K. and Tavantzis S.M.  Quinic acid induces hypovirulence and expression of a hypovirulence-associated double-stranded RNA in Rhizoctonia solani. Current Genetics 43: 103-111.

2000. Strauss, E.E., Lakshman, D.K., and Tavantzis, S.M.  Molecular characterization of the genome of a partitivirus from the basidiomycete Rhizoctonia solani. Journal of General Virology 81: 549-555.

1998. Lakshman, D.K., Jian, J. and Tavantzis, S.M.  A double-stranded RNA element from a hypovirulent strain of Rhizoctonia solani occurs in DNA form and is genetically related to the pentafunctional AROM protein of the shikimate pathway. Proceedings of the National Academy of Science, USA 95: 6425-6429.

1998. Jian, J., Lakshman, D.K. and Tavantzis, S.M.  A virulence-associated, 6.4-kb, double-stranded RNA from Rhizoctonia solani is phylogenetically related to plant bromoviruses and electron transport enzymes. Molecular Plant-Microbe Interactions 11: 601-609.

1997. Jian, J., Lakshman, D.K. and Tavantzis, S.M.  Association of distinct double-stranded RNAs with enhanced or diminished virulence in Rhizoctonia solani infecting potato. Molecular Plant-Microbe Interactions10: 1002-1009.  (cover page article)

1995. Castello, J.D., Lakshman, D.K., Tavantzis, S.M., Rogers, S.O., Bachand, G.D., Jagels, R., Carlisle J. and Liu, Y.  Detection of infectious tomato mosaic virus in fog and clouds. Phytopathology 85: 1409-1411.

1994. Lakshman, D.K. and Tavantzis, S.M.  Spontaneous appearance of genetically distinct double-stranded RNA elements in Rhizoctonia solani. Phytopathology 84: 633-639.

1994. Singh, R.P., Boucher, A., Lakshman, D.K. and Tavantzis, S.M.  Multimeric non-radioactive cRNA probes improve detection of potato spindle tuber viroid (PSTVd). Journal of Virological Methods 49: 221-234.

1993. Lakshman, D.K., and Tavantzis, S.M.  Primary and secondary structure of a 360-nucleotide isolate of potato spindle tuber viroid. Archives of Virology128: 319-332.

1992. Lakshman, D.K., Tavantzis, S.M., Boucher, A., and Singh, R.P.  A rapid and versatile method for cloning viroids or other circular plant pathogenic RNAs. Analytical Biochemistry 203: 269-273.

1992. Lakshman, D.K., and Tavantzis, S.M.  RNA progeny of an infectious two-base deletion cDNA mutant of potato spindle tuber viroid (PSTV) acquire two nucleotides in planta. Virology 187: 565-572.

1992. Singh, R.P., Lakshman, D.K., Boucher, A., and Tavantzis, S.M.  A viroid from Nematanthus wettsteinii plants closely related to the columnea latent viroid. Journal of General Virology 73: 2769-2774.

1989. Hiruki, C., Lakshman, D.K., and Figueiredo, G.  A comparative study of the sensitivity of dot Hybridization assays using cRNA and cDNA for the detection of potato spindle tuber viroid. Proc. Japan Acad. Ser. B. 65: 76-79.

1987. Rao, A.L.N., Lakshman, D.K., Ohki, S.T., and Hiruki, C.  Identification of a new serotype and antigenic relationships among six strains of red clover necrotic mosaic virus. Phytopathology 77: 995-999.

1986. Lakshman, D.K., Hiruki, C., Wu, X.N., and Leung, W.C.  Use of [32P] RNA probes for the dot-hybridization detection of potato spindle tuber viroid.  Journal of Virological Methods 14: 309-319.

1985. Lakshman, D.K., and Gonsalves, D.  Genetic analyses of two large lesion isolates of cucumber mosaic virus. Phytopathology 75: 758-762.

1985. Lakshman, D.K., Gonsalves, D., and Fulton, R.W.  Role of Vigna species in the appearance of pathogenic variants of cucumber mosaic virus.  Phytopathology 75: 751-757. 

TECHNICAL REPORTS:
2011. Lakshman, D.K., Amaradasa, S., and B. Horvath.  Identifying pathogens causing brown patch disease. Golf Course Management 79(5): 99.

2010. Lakshman, D.K. and Natarajan, S.S.  Understanding the biology and pathology of a soilborne fungus Rhizctonia solani through proteomic investigations. The Journal of Plant Protection Sciences, 2(1): 105.

2009. Lakshman, D.K.  Accurate Identification and Gene Expression in Relation to Virulence of Rhizoctonia Isolates Infecting Turfgrasses . (http://turf.lib.msu.edu/ressum/2009/9.pdf).

2008. Natarajan S.S. and Lakshman DK.  Proteomic investigation of Rhizoctonia solani to understand its biology and pathogenicity. Association for Advancement in Plant Protection 3(2): 2.

2008. Lakshman, D.K.  Accurate Identification and Gene Expression in Relation to Virulence of Rhizoctonia Isolates Infecting Turfgrasses .  (http://turf.lib.msu.edu/ressum/2008/15.pdf).

2008. Lakshman, D.K.  Arboretum scientists are exploring nature friendly ways to control soilborne plant diseases. Arbor Friends, Winter issue.  P 9.  (Popular Article).

2007. Lakshman, D.K. Accurate Identification and Gene Expression in Relation to Virulence of Rhizoctonia Isolates Infecting Turfgrasses. (http://turf.lib.msu.edu/ressum/2007/18.pdf).

2006. Lakshman, D.K.  Double-stranded RNA-mediated hypovirulence in Rhizoctonia solani. Society for Advancement in Plant Protection 1(1): 3.  (Technical Report).

2006. Lakshman, D.K.  Restructuring Agri-education in India. Society for Advancement in Plant Protection. 1 (3): 4-5.

1993. Lakshman, D.K. and Tavantzis, S.M.  Cloning of circular plant pathogenic RNAs. Rice Biotechnology Quarterly, 13:28.

BOOK CHAPTERS:

2010. Ressom, H., Lakshman, D.K., Yun, S.J., Pramanik, S.K., and de los Reyes, B. G.  Microarray Data Analysis using Machine Learning Methods, pp. 1-32. In Nag A. (ed.) Biosystems Engineering, McGraw-Hill, New Delhi, 544 pp. 

2009. de los Reyes, B.G., Lakshman, D.K., Yun, S.J., and Ressom, H.  Agricultural Genomics, pp. 55-88. In Nag. A. (ed.) Textbook of Agricultural Biotechnology, Prentice-Hall of India, 260 pp. 

2002. Tavantzis, S.M., Lakshman, D.K., and Liu, C.  Double-stranded RNA elements modulating virulence in Rhizoctonia solani pp. 191-211. InTavantzis, S.M. (ed.) dsRNA genetic elements – Concepts and applications in agriculture. Forestry, and medicine, CRC Press, Florida. 284 pp.

1996. Rubio, V., Tavantzis, S.M. and Lakshman, D.K.  Extra-chromosomal elements and degree of pathogenicity in Rhizoctonia solani pp. 127-138. In Sneh, B., Jabaji-Hare, S., Neate, S., and Dijst, G. (eds.) Rhizoctonia Species: taxonomy, molecular biology, ecology, pathology and disease control, Kluwer Academic Publishers, The Netherlands. 578 pp.

1995. Tavantzis, S.M. and Lakshman, D.K.  Virus-like double stranded RNA elements and hypovirulence in phytopathogenic fungi, pp. 249-267. In Kohmoto, K., Singh, R.P., and U.S. Singh, U.S. (eds.)Pathogenesis and Host-Parasite Specificity in Plant Diseases: Histopathological, Biochemical, Genetic and Molecular Basis, CRC Press. 1226 pp. 

GenBank DEPOSITS:
(Submitted 11 full-length cDNA sequences of viruses, viroids and fungal genes, several bacterial genes with roles in plant colonization and biocontrol, and 1888 EST contigs of a soilborne basidiomycetous plant pathogenic fungus R. solani AG 4 (AF631311 to AF633198).

Selected accessions:
Arom               Aromatic amino acid synthesis (arom) gene of R. solani (AF482690)
M1                   Virus-like dsRNA of R. solani, isolate Rhs 1AP (AF020042)
M2                   Virus-like dsRNA of R. solani, isolate Rhs 1A1  (U51331)
dsRNA1          Partitivirus of R. solani, isolate Rhs 717  (AF133290)
dsRNA2          Partitivirus of R. solani, isolate Rhs 717  (AF133291)
PSTVd-M        Mild strain K-5, potato spindle tuber viroid  (M93685)
PSTVd-M        Genomic variant, KF-5/M3  (AF483470)
PSTVd-M        Genomic variant, KF-5/M4  (AF483471)
PSTVd-S         Severe strain, host repaired mutant, St4/17  (AF483472)
PSTVd-S         Severe strain, host repaired mutant, St4/22  (AF483473)    
CLVd              Strain of Columnea latent viroid  (M93686)

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