The Role of Calcium in Mediating Smut Disease Severity and Salt Tolerance in Corn under Chloride and Sulphate Salinity

The effect of sahne irrigation water containing NaCl or Na2SO4 with and without CaSO4 application on the gram yield, smut index and plant nutrient contents of two intermediate smut-susceptible corn cultivars was investigated in cemented plots containing sandy loam soil. The plants were artificially infected and the disease severity was rated. At the end of silking stage, the leaf Cl, Na and Ca contents were detected and Ca/Na ratio was calculated. At harvest, the grain yield of smut-free and smutted plants was recorded. The results showed that NaiSOi-treated plants had a greater yield advantage than those exposed to NaCl-treatments. The inclusion of CaSO4 was beneficial to both salinity types and improved the yield potential. Similarly, smut susceptibility was reduced by 10.8% for the Na2SO4-stressed plants, compared with 22.7% for NaCl treatment. The comparable reductions in disease severity associated with Ca supply dropped to 33.0 and 17.0%, respectively, indicating the beneficial contribution of a Ca supply on the mediating disease reaction. Although the smut index was markedly decreased as the leaf C! content increased in Ca-deficient plants stibjected to saline irrigation water without Ca supply, the increase in the Ca/Na ratio in plant tissue, associated with supplemental CaSO4 application to each salinity type, appeared to have an additive effect on smut disease control and salt tolerance.