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Enhancement of Diagnostic Symptoms of Potato Spindle Tuber Virus by Manganese. C. R. Lee, Research Scientist, Canada Department of Agriculture, Research Station, Fredericton, New Brunswick, Canada; R. P. Singh, Research Scientist, Canada Department of Agriculture, Research Station, Fredericton, New Brunswick, Canada. Phytopathology 62:516-520. Accepted for publication 1 December 1971. DOI: 10.1094/Phyto-62-516.

Although the tomato cultivar Allerfrüheste-Freiland has been used successfully as an indicator host for the mild strain of the potato spindle tuber virus (MPSTV), at times some inconsistency in symptom expression has been encountered. Involvement of manganese nutrition was suspected. Tomato plants were grown in sand cultures containing various levels of Mn, Fe, or Zn. Increasing Mn in the growth medium from 0 to 9 µg/ml dramatically increased the characteristic veinal necrosis symptoms induced by MPSTV and the severe strain. Extensive virus-induced necrosis was obtained whenever Mn contents of plant tissue were 1,500 µg/g or above and Mn/Fe concentration ratios were 12 or more. In sand cultures containing 9 µg/ml of Mn, increasing Fe in the growth medium up to 10 µg/ml decreased tissue Mn/Fe ratios below 12, and resulted in less virus-induced necrosis. Zinc had no effect on virus-induced necrosis. Other tomato cultivars (Bonny Best, Michigan-Ohio, Rutgers, and Sheyenne), reported previously as symptomless carriers of MPSTV, developed virus-induced necrosis when grown in sand cultures receiving 9 µg/ml of Mn.