دراسة تأثير التغطية بالبولي اثلين واليوريا كعامل استحثاث مقاومة في امراضية بعض عزلات الفطر Alternaria alternata وتشخيصها جزيئيا

Studying the effect of Polyethelene coverage and urea as an induction factor of resistance in pathogenicity of some isolates of Alternaria alternata and partially diagnosed

       A series of laboratory experiments was conducted in the laboratory and Field of Department of Plant   Protection – Faculty of Agriculture – University of Karbala , from all of these experiments could be study the pathogenicity of four isolates of the fungus Alternaria alternata (AK, AB, AM2, AM1) was tested on cress and tomato seeds and produce oxalic acid , the isolate AM2 Through pathogenicity test on cress seeds and tomatoes for the production of oxalic acid  show that more pathogenic  isolate was AM2 , germination percentage of the cress seeds and tomatoes was 0.0% for both , inhibition percentage was 100%. Then , in AB isolate, germination percentage of the cress seeds was 4.4% and tomatoes 0.0% and inhibition percentage was 49.97% , 100% respectively. Then ,in AM1 isolate, germination percentages of the cress seeds and tomatoes were 8.86% and 73.33% respectively, while the inhibition percentages of the cress seeds and tomatoes were 89.87% 22.9%  respectively. The less pathogenic  isolate was AK , the germination percentages of the cress seeds and tomatoes were 60.0% and 83.66%  respectively and the inhibition percentages of the cress seeds and tomatoes were 31.42% and 12.12% respectively, was the highest producer of  this acid reached to14 x 10^-2.

        The four isolat were  identified by Polymarase Chain Reaction   (PCR)  technique using primer)aa-hsp) pair all  isolates were found to be  similar through DNA analysis .

        The results showed that the best temperatureof fungus growth  was 25 ˚m , the results also showed that the covered sterilized soil and urea have had a significant effect on the pathogenic of  isolated  AM2 .

          The results of the field experiment to sterilize the soil and covering show a significant effect on the length of the shoot of tomatoes , wet weight , dring weight , root length,  wet weight of root and dring weight , rates were 57.86, 67.88 c.m, 51.72, 52.48 g.m,23.54 , 23.81 g.m , 48.47 , 48.16 c.m,18.91 , 18.90 g.m , 8.80 and 8.34 g.m respectively.

     The sterilize the soil , covering , adding urea with 1g/k.g and the fungus the disease percentage shows significant effect on disease percentage on tomatoes, the rates were  28.86% , 25.13% 11.45% and  45.86% respectively, The sterilize the soil show no effect on the disease severity , it was 17.10% , while covering the soil with Polyethylenes , use the urea with 1g/k.g and adding fungus show a significant effect on disease severity , its were 15.89%, 3.38% and  23.90% respectively .