Irrigation Water Composition Alters Plant Mineral Composition and Rapid Blight on Perennial Ryegrass.
James Camberato, Purdue University, Agronomy 2-452, 915 W. State Street, 915 W. State Street, West Lafayette, IN 47907-2054, United States of America, Paul D. Peterson, Clemson University, Pee Dee Research and Education Center, 2200 Pocket Road, Florence, SC 25905, and S. Bruce Martin, Clemson University - Pee Dee Research and Education Center, 2200 Pocket Road, Florence, SC 29505.
Rapid blight, caused by Labyrinthula terrestris (D.W. Bigelow, M.W. Olsen, and Gilb.), increases with increasing irrigation water salinity. Irrigation waters from Western (WW) and Eastern (WE) regions of the United States, where rapid blight occurs, have different chemical composition. Notably higher concentrations of Ca occur in WW, while WE waters have considerable HCO3. Perennial ryegrass was grown with irrigation water varying in Na, Ca, Mg, Cl, SO4, and HCO3 to represent water from each region, 3 levels of electrical conductivity (≈ 0.1, 2.5, and 4.6 dS/m), and 3 types of inoculation (none or a composite of 4 Western or 4 Eastern isolates of L. terrestris). Chlorotic leaf tissue (LC) was rated thrice per week and shoot dry matter (DM), moisture content (MC), and chemical composition were determined ≈ 45d after water treatments were initiated. Eastern water reduced DM and MC and increased LC more than WW at 2.5 and 4.6 dS/m, and at greater magnitude when inoculated. Shoot Na was higher and Ca and K were lower with WE than WW. Tissue chlorosis correlated best with tissue Na across water compositions, salinity, and inoculation treatments (r>0.80). Tissue K was negatively correlated with LC. Tissue mineral concentrations resulting from different water composition and EC may foster the development of Labyrinthula, weaken the plant so it is more susceptible to the organism, and/or be correlated with other factors related to disease development.