This is the report from a BSPP Senior Fellowship.
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For me, it was a dream come true in November last year, when I arrived CAES for my 3 months visit studying nanoparticles and Fusarium disease with Dr Wade Elmer. Dr Elmer has studied the use of nanoparticles of metallic oxides and composites to suppress plant diseases through altering host defense pathways. Even though this was my first nanoparticle and plant disease research, I was however very comfortable and excited, working with some of the very best in the field. Apart from my host Dr Elmer, who is the Head of Department of Plant Pathology & Ecology/Vice Director of CAES, also involved in the investigation was Dr Jason White (State Chemist/Director of CAES) and Dr Christian Dimkpa (Head of Analytical Chemistry, CAES). CAES was founded in 1875 and is the oldest Agricultural Experiment Station in the US, and one of the most reputable research institutions, conducting research in the areas of Entomology, Plant Pathology, Environmental Sciences, Forestry and Horticulture, Analytical Chemistry, and Vector Biology and Zoonotic Diseases. Many of CAES scientists are also affiliated with nearby universities including Yale University and University of Connecticut, where they teach, advise students, and conduct research.
At CAES, I investigated the role of nanoparticles of CuO in suppressing root rot caused by Fusarium virguliforme on genetically modified soybeans. Fusarium virguliforme is a root fungal pathogen that causes sudden death syndrome (SDS) to soybean (Glycine max). SDS is widespread in the United States and has resulted in $3.06 billion in losses. Fusarium virguliforme resides in the soil, infects roots and colonises xylem and phloem elements. The export of toxins to the shoots, along with physically restricted water and nutrient transport, compromises photosynthesis, growth and yield. Early symptoms include poor root development, foliar chlorosis and/or necrosis, and defoliation; however, symptoms often intensify at flowering, followed by rapid mortality. SDS management has been difficult, although crop rotation and improved soil drainage offer some benefit. Given the suppressive effect of nanoscale micronutrients on the disease, investigation into this approach for SDS was pursued.
Engineered nanoparticles (NP) (<100 nm) of metalloid and metal oxides have great potential in agriculture as a means to deliver micro-nutrients to plants. It is well documented that the micronutrients B, Cu, Mn, and Zn can play pivotal roles in plant health by activating important enzyme systems. Because micronutrients, in general, have poor basipetal and intra-plant mobility and are less available in neutral soils, compromised nutrition of the plant roots often results in increased susceptibility to wilts and root rots. Past research involving CAES scientists demonstrated that CuO NP and other metal oxide micronutrients possess the potential to fertilise roots of eggplant, maize, and tomato, when applied foliarly, presumably due to nano-enabled basipetal translocation. For instance, tomato and eggplant roots had more Cu when the leaves were exposed to CuO NP and had less disease when these plants were grown in soil with Fusarium oxysporum f. sp. lycopersici or Verticillium dahliae, respectively. The role of NP in delivering nutrition for disease management is otherwise largely unexplored.
Two greenhouse experiments were conducted to compared the CuO nanoparticles in suppressing Fusarium root rot of conventional glyphosate-susceptible soybeans or genetically modified glyphosate resistant soybeans. The experiment was conducted with 10 replicates per treatment. Seed were germinated on and treated at 4 weeks after planting with CuO nano sheet applied at 500 PPM. The plants were exposed to the NP treatments by inverting the seedling and then immersing the leaves into the NP suspensions for 3−5 seconds, followed by hanging the seedlings upside down until dry. Plants were then transplanted into infested or noninfested potting mix. In this trial, there were 10 replicates and plants were arranged on greenhouse benches. Plants were transplanted into soil infested with Fusarium virguliforme applied at 2 g / liter potting soil or into non infested soil. One week later plants were treated with glyphosate herbicide. After 5 weeks fresh and dry weights along with the percent root rot were determined and the data analysed using the SYSTATV.10 (Cranes Software International Limited). Disease reduced fresh weights by 40%. An interaction was detected between the two soybean cultivars and NP. On glyphosate susceptible cultivars, NP increase fresh weights by 17%, but glyphosate tolerant plant showed a 11 % decrease in fresh weight after being exposed to NP. NP of CuO also increased the fresh weight of glyphosate susceptible soybeans that were exposed to glyphosate, but had no effect on glyphosate tolerant plant when they were treated with NP of CuO and sprayed with glyphosate. These preliminary findings suggest the use of NP differ on soybean cultivars in the presence of Fusarium and glyphosate herbicide.
I am very thankful to BSPP for awarding me the BSPP Senior Fellowship, without which this visit/investigation would have not been. I also thank Drs Elmer and White for giving me the opportunity to collaborate and contribute to their programs advancing plant health and I look forward to a continued interaction.
Dr Sylvester Aigbe
Ambrose Alli University, Ekpoma, Nigeria
