استحثاث المقاومة المكتسبة الجهازية في نبات البندورة-الطماطم إزاء مرض اللفحة المبكرة المتسبب عن الفطر Sorauer (Ellis and Martin)‎ Alternaria solani باستخدام حمض الساليسيليك

الملخص EN

Early blight (EB) caused by Alternaria solani Sorauer (Ellis & Martin) fungus is one of the important fungal diseases on tomato plants causing significant losses in yield and quality.

This research was carried out in the laboratories of the Biological Control Studies and Research Center, Faculty of Agriculture, Damascus University to study the role of salicylic acid in stimulating tomato plant to resist the early blight disease.

The effect of salicylic acid was studied in vitro to inhibiting the growth of fungal pathogen’s mycelium on the PDA culture medium using three concentrations (0.5, 1.0, 1.5 micromole/liter).

Field tests by spraying tomato plants with salicylic acid concentration of 1.5 micromole/liter before spraying these plants with conidial suspension of the pathogenic fungus at a concentration of 5*106 conidia/ml.

Laboratory results showed high efficiency of salicylic acid in the inhibition of fungal mycelium, reaching 100% at a concentration of 1.5 micromole/liter, whereas in the field, the results showed a clear decrease in the disease severity on the leaves and fruits of plants treated with a conidial suspension and salicylic acid compared to plants treated with a conidial suspension only.

Seven days after treatment, disease severity on leaves treated with salicylic acid of the Shorouk variety reached 4.89%, whereas disease severity increased to 13.44% for the same variety when treated with conidial suspension only.

Highest disease severity of 24.01% was recorded on the tomato variety Balad and decreased to 10.34 % when treated with salicylic acid.

Disease severity on tomato fruits was also higher on Balad variety which reached 4.17% and decreased to 1.58% when treated with salicylic acid.

28 days after treatment, results showed an increase in disease severity for both treatments, with a clear decrease in the treatment with salicylic acid on leaves and fruits and for all varieties.

Results suggest that there is a factor that induced tomato plants sprayed with SA which reduced disease severity.

In an effort to find out why, proteins were extracted from tomato plants treated with salicylic acid and from non-treated plants and separated by electrophoresis in polyacrylamide gel.

The results obtained showed an increase in the size of protein bands and the appearance of new protein bands in plants sprayed with salicilic acid, whereas these bands did not appear in samples of tomato plants not treated with salicylic acid.

Thus, these proteins induced in tomato plants are likely responsible for inducing systemic acquired resistance (SAR) in tomato plants and stimulated resistance R-genes to produce pathogenesis-related proteins (PRP) responsible for fungal resistance.