تأثير بعض المحفزات الأحيائية في مقاومة نبات الفراولة الفريز ضد الفطر Tassi)‎ Goild phaseolina Macrophomina)‎ المسبب لمرض تعفن الجذور و الساق

الملخص EN

The causal agent of charcoal root and basal stem rot of strawberry was isolated and characterized.

The pathogenicity of fungal isolates obtained from symptomatic strawberry plants collected from different locations in Baghdad and Kerbala was established.

Activity of the bacteria Bacillus subtilis, B.

thuringiensis and Pseudomonas fluorescens and the fungus Trichoderma viride to induce systemic resistance in the plants against Macrophomina phaseolina under laboratory and greenhouse conditions were evaluated.

Results showed that nine isolates were pathogenic to strawberry.

The highest infection rate was obtained with the isolate MK3 (85.0%).

All used bioagents reduced the growth of MK3 isolate, on PDA.

The highest reduction of MK3 growth was obtained with P.

fluorescens (1.17 cm) compared to 3.67 and 3.35 cm for B.

subtilis and B.

thuringiensis, respectively.

Highest antagonism was induced by T.

viride against MK3 isolate.

Beltanol application in PDA plates at 500, 750 and 1000 mg/L caused reduction in MK3 isolate growth, that reached 7.42, 4.72 and 0.00 cm, respectively.

All the bioagents used significantly reduced the infection rate and disease severity induced by MK3 by 5.00% and 2.50% with T.

viride, 10% and 7.50% with P.

fluorescens compared to 77.50% and 70.00% for the control, respectively.

Increase in root length, and root and biomass dry weight was also observed.

The highest increase was observed in infected plants treated with T.

viride compared to untreated MK3 control.

Treatment with bioagents significantly increased peroxidase activity in strawberry plants.

Peroxidase activity increased up to 67.48 unit/ml with T.

viride treatment as compared with 23.97 unit/ml in the control treatment