Effects of Tetracycline Antibiotics on Plants Affected by Legume Little Leaf Disease

Abstract

Nicotiana glutino8a, aster, and tomato plants affected by legume little leaf disease were treated by spraying the foliage with 100 ,..,g/ml aqueous solutions of either Achromycin (tetracycline hydrochloride) or Aureomycin (chlortetracycline hydro-chloride), every 2-3 days for periods of 4-8 weeks. Disease symptoms were sup· pressed in the new growth of all plants during the treatment period, but reappeared 2-4 weeks after the last application of antibiotic. Mycoplasma-like bodies were abundant in the phloem sieve tubes of untreated aster, and in aster which redeveloped symptoms after the antibiotic treatment had been discontinued. In contrast, Mycoplasma·like bodies could not be detected by thin· section electron microscopy in symptomless shoots of Achromycin-treated plants immediately after a period of treatment. In concomitant leafhopper transmission tests with the vector Orosius argentatus, the little leaf agent was not recovered from the symptomless treated shoots, but was readily recovered from diseased shoots which developed after termina-tion of the Achromycin treatment.