Influence on the resistance toward the pathogen fungus Fusarium circinatum after exogenous application of methyl jasmonate (MJ) on seedlings of maritime pine (Pinus pinaster) was investigated. The impact of different concentrations of NPK (nitrogen, phosphorus, potassium) fertilizers on the growth and development of seedlings and consequently the effects of particular nutrients on the seedling resistance against the fungus was also examined. Pitch canker is a quarantine disease that can affect all species of pine, especially in nurseries and plantations. The experiment was performed on 3 months old seedlings of P. pinaster. The seedlings were divided into 4 blocks; each of them consisted of 9 groups with different NPK treatments. Seedlings in two blocks (III and IV) were treated with 25 mM of MJ. A day later, they were infected through wounds with F. circinatum. The symptoms weremonitored for 8 weeks. We have observed that MJ had no effect on better resistance; the mortality was even higher than in untreated seedlings. MJ had a negative influence on the growth of apical meristems. Possible cause could be the toxicity of MJ. There was no difference in the number of traumatic resin ducts between treated and untreated seedlings. Large concentrations of fertilizer in the substrate provoked the seedlings to grow faster and bigger, albeit lowering the resistance toward the fungus. The treatment with nitrogen especially lowered the plant resistance. Phosphorus caused stronger growth of the seedlings root system. No specific change was observed after treatment of plants with potassium.
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