دور درنات البطاطا البطاطس المصابة طبيعياً بالجرب (Streptomyces scabies)‎ و الدرنات المعداة بالعامل الممرض في نقل الجرب إلى الدرنات الناتجة و تلويث التربة

الملخص EN

Two field experiments were carried out in spring 2009 at Idleb Research Center.

In the first experiment, naturally scabbed potato seed tubers with different infection levels ranged from no scab symptoms (M0) to more than 10 lesions/seed tuber (M5) were used, in addition to a control treatment with scab free potato seed tubers obtained from the General Organization for Seed Multiplication in Idleb.

In the second experiment, scab-free potato seed tubers were inoculated with different concentrations of suspensions of pathogenic Streptomyces scabies (five densities) from 2.3×102 to 8.1×106 cfu/tuber.

Potato cultivar Spunta was used.

After harvest, scab incidence, severity and soil contamination were evaluated.

Results showed that scab incidence and scab severity increased with increasing number of lesions in the first experiment, and in density of seed-borne pathogenic inoculum on surface of seed tubers in the second experiment.

Scab incidence in the first experiment was between 22.1 and 33.1% for the first (M0) and last treatment (M5), respectively.

In the second experiment, scab incidence was between 24.4 and 66.4% for inoculum density 2.3×102 and 8.1×106 cfu/tuber, respectively.

No scab symptoms appeared on tubers produced from the control treatment.

Significant differences were obtained between the control and other treatments for both experiments, and between the last treatment (8.1×106 cfu/seed) and other treatments in second experiment.

Scab severity increased significantly in both experiments.

In the first experiment, scab severity was about 5% on more than 50% of infected tubers, whereas scab severity was more than 50% in 30% of infected tubers in the second experiment.

Results of soil analysis after harvest showed that contamination with pathogenic bacteria in both experiments were between 1.2×102 and 9.8×103 cfu/g of soil.

These densities are sufficient to cause scab disease on tubers in the following seasons.

Results of this study showed that it may be possible to predict scab incidence and severity that could develop by the end of the growing season, if seed tuber infection was determined.