الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Potato (Solanum tubersum L.) is the world’s fourth most consumed crop, yielding an estimated 374 million tons of production worldwide, obtained from nearly 17,623,660 hectares. Potato is considered as one of Egypt’s most significant vegetable crops, with a production total of 4,325,478 tons from around 163,939 hectares, making Egypt the second largest potato producer after Algeria. In this study, there are six isolates from R.solani from six different farm geographical localities in Egypt and three potato cultivars, namely, Spunta, Cara, and Lady Rosetta, that were used throughout the present study.
The main results were:
1. The results were obtained cleared that the highest pathogenicity was recorded by R.solani (Rs3) against the mean plant height of potato cultivar (Spunta )(7.00), whereas, the least effect was achieved by (Rs1) (14.33). For the potato cultivar Cara the highest pathogenicity was recorded by (Rs4) against the mean plant height of potato (0.0), while the least effect accrued by (Rs1) (15c). Finally, when studied the efficiency of different isolates of Rhizoctoniasolani against potato cultivars (Lady Rosetta ). The highest pathogenicity was achieved by Rs4 against the mean plant height (3.67). But, the least effect was recorded by Rs5against the mean plant height (11).
2. The number of plants was detected after the treatment by different isolates of R.solani against potatoes cultivars. The results were showed that the highest pathogenicity was recorded byR.solani (Rs4) against the mean number of the plant of potato cultivar (Spunta )(1.00), whereas, the least effect was achieved by (Rs2), (Rs3) (Rs5), and (Rs6) with the nearly the same pathogenesis (1.67). For the potato cultivar Cara the highest pathogenicity was recorded by (Rs4) against the mean number of plant height of potato (0.0), while the least effect was recorded in (Rs1) (2.67). Finally, the results specific to the third type from cultivars is (Lady Rosetta) showed that the highest pathogenicity was achieved by Rs4 and Rs5 against the mean number of the plant(0.67) for both isolates. While the lowest pathogenicity isolates were recorded by Rs6 against the mean number of the plant (2.33).
3. The total amplification fragments were detected for the 6 isolates as follow:
10 (R1), 4 (R2), 18 (R3), 16 (R4), 18 (R5), 2 (R6), The highest amplification fragments were recorded in isolate number 3 and 5, while isolate number 6 showed the lowest fragments Among the investigated isolates, the obtained maximum numbers of fragments was 18 fragments. On the other hand, the minimum numbers of fragments was 2 fragments.
4. The genetic similarities among the tested 6 R. solani isolates were illustrated in , Cluster can be divided into two main groups. the first group includes R. solani isolate number 5, while the second group includes the rest of the tested isolates together Within the second cluster divided into two groups with 10% genetic similarity, i.e., the first one includes R. solani (R6), whereas the second one (20% genetic similarity) includes R1, R2, R3 and R4 isolates together .
5. The results of the alcoholic and water extracts of the different plant extract showed that the black seed with different concentrations in alcoholic extract in 20%, 40 %, and 60% was recorded low inhibition while in 80% and 100% recorded a complete inhibition in the growth of the isolates. All the concentrations of water extract of the black seed that were used showed a low inhibition effect on all isolates.
6. The results of the alcoholic extract of liqurice with different concentrations in 20% and 40 % were recorded low inhibition while, in 60%, 80%, and 100% complete inhibition detected on isolates growth. In all concentrations of water, extract was used showed no effect on all isolates.
7. The results of the alcoholic extract of lemongrass with different concentrations in 20% and 40 % were shown low inhibition on fungal growth while, in 60%, 80%, and 100% more inhibition on the growth of the isolates were detected. While the water extract in all concentrations showed a very low effect on the growth of all isolates.
8. The results of the alcoholic extract of castor oil with different concentrations in 20% vedoes not affect the fungal growth in all isolates and 40 % and 60% showed more inhibition effect on all isolates while 80% and 100 showed complete inhibition in fungal growth in all isolates. While the water extract in all concentrations showed a high inhibition effect on fungal growth on all isolates.