Jeremey Gneck and Dr. Brad Geary, Plant & Wildlife Sciences
Each year potato yields are reduced due in part to root pathogens such as the fungus Colletotrichum coccodes (Black Dot). Research interactions among Russet Burbank potatoes, C. coccodes and mineral nutrition will be conducted in hydroponic growth chambers in order to determine the optimal concentration of phosphorus, a necessary macro-nutrient required in plants for growth and disease resistance. The expected outcome of this research will determine the necessary concentration of phosphorus that will boost the plant’s natural resistance to the C. coccodes fungus without adversely affecting the plant. This research will then be added to prior studies that have measured the optimal concentrations of other macro-nutrients nitrogen and potassium to provide a comprehensive overview to disease resistance in connection with mineral concentrations. The data produced through this study will provide farmers with an inexpensive and natural alternative to fungicides or other disease controlling chemicals that can be harmful to the environment and their crops.
Russet Burbank potatoes were grown in a hydroponic solution containing all necessary minerals for plant growth. Phosphorus was added in four concentrations; the pathogen C. coccodes was also added as a 20 ml (10,000 spores/ml) aliquot. As an initial step to the study, hydroponically grown potatoes were treated with eight varying concentrations of phosphorus to determine the concentrations that are: deficient, adequate, ideal, and toxic to plant growth. This initial phase of the study was conducted for four weeks providing time for the plantlets to grow. At the end of the four week growth period, the plants were measured and harvested. By measuring the bio-mass of the potato plants at each level of phosphorus treatment, the four concentrations were confirmed by weighing dried plant biomass. The data gathered from this preliminary study was then applied to the second phase of the project which determined ideal concentrations of phosphorus, based on plant growth, and the reduced presence of C. coccodes.
The initial phase of the experiment was conducted during a four-week time period in which three times a week dissolved phosphorus was added to a modified Hoagland solution where the potato plantlets were grown. The amount of phosphorus added, ranged from a concentration representing a nutrient deficiency(0.5 mg/L), to an overabundance of phosphorus (64 mg/L)in the solution. In order to monitor the nutrient levels for each concentration, hydroponic systems were arranged in a climate controlled and light timed growth chamber. At the end of the four week period both qualitative and quantitative analyses were performed measuring plant reaction to the treated nutrient level. Phosphorus levels were evaluated quantitatively through tissue analysis using the nitric-perchorlic acid digestion on an IRIS Intrepid II XSP machine (Thermo Scientific Electron, Waltham, Ma). Qualitative observations such as appearance in plant color and size provided a visual indication of the plant’s response to the phosphorus concentration. Whereas, measuring the bio-mass of the plant provided a quantitative analysis that correlated plant size to phosphorus concentration as seen through the distribution of a bell-curve. Taking the information gathered from this preliminary study, we then repeated the process of growing potato plantlets in a modified Hoagland solution limiting the varying phosphorus treatment to our four selected concentrations: 0.5, 2, 16, and 128 mg/L of phosphorus. These concentrations again represented a range of deficiency to overabundance of nutrient with an ideal amount falling between these extremes. Treatment applications were identical to the preliminary study, allowing for an appropriate growth period. At the end of the growth period, plantlets were inoculated with spores per of C. coccodes (40ml) at four different locations within the bucket containing the hydroponic solution (pathogen was cultured and maintained on a potato dextrose agar until needed for inoculation). Ten days after inoculation, plant stems and roots were harvested for qPCR analysis as well as Root Colonization Assay.
Results produced from the Root Colonization Assay displayed a direct correlation between phosphorus concentrations and infection severity of the potato plant. The data produced showed a digression of plant infection in relation to phosphorus concentration with the most significant decrease in infection at (32 mg/L). The data collected from the qPCR analysis supported this conclusion and demonstrated that nutrient concentration influences a potato plant’s ability to resist infection from C. coccodes.
The findings of this study were shared at the Potato Association of America annual meeting. I am currently preparing to publish my findings in a peer reviewed journal.