The interaction of Rhizoctonia solani and Meloidogyne incognita Race 3 and Race 4, was tested on four cultivars of American cotton namely RNR-120, RNR-315, DP-50 and Auburn-634.The obtained data revealed that the artificial infection to the susceptible cultivar DP-50 with the fungus in combination with either nematode races increased the root galling from 25-30% in case of nematode alone to 30-40% respectively. Combined infection also increased the pre-emergence damping-off from 60% in case of fungal infection alone to 80%. At the same time the root necrosis of the same cultivar was increased by 25-30% in the combined infection. The second susceptible cultivar to nematode (RNR-315) gave almost similar results in which the pre emergence damping-off was increased from 40% in fungal infection alone to 80% in the combined infection with either races 3 or 4 of the nematode. However, galling and root necrosis were not affected by combined infection.Both cotton cultivars RNR-120 and Auburn-634 were resistant to nematode infection. On the other hand, the pre-emergence damping-off of the cultivar RNR-120 was increased from 80% to 100%, when the race 3 was combined with the fungus. Galling and root necrosis were increased from 10% to 30% under the combination between the fungus and either nematode races 3 and 4. Also, the results showed that cv Auburn-634 was resistant to both nematode races but susceptible to the fungus. Such data revealed that the synergistic effect is limited to susceptible cotton cultivars to nematodes, whereas the nematode resistant cultivars did not affected much by the combined infection of the fungus plus nematode.

The quantitative and qualitative contents of free and total amino acids were estimated in hyphae of six isolates of Rhizoctonia solani. Such isolates were varied in their virulence on bean (Phasiolus vulgaris) Giza-3 cultivar. It has been found that the mycelium of the high virulent isolates (4,5,6) contained higher amounts of total amino acids than that of the less virulent isolates (1,2,3). The mean content of lucine was the highest 1760.76 mg/100g fresh weight of the total amino acids of all fungal isolates. However, the least means of total amino acids were found with proline 107.352 mg/100g f.w and cystine 16.710. The rest of total amino acids were varied between the fungal isolates in which the high virulent isolates (4,5,6) contained high amount of Glutamic (1086Glutamic ( .164, 1245Glutamic ( .230 and 2202 mg/100g f.w respectively), Glycine (1346Glycine ( .484, 1431Glycine ( .663 and 2530.702 mg/100g f.w respectively) and lucine (2009.396, 2194.982 and 3465.961 mg/100g f.w respectively). On the other hand Histidine was found also in high concentration (755.084 mg/100g f.w) in hyphae of the high virulent isolate No.6 which could be related to virulenc.In case of free amino acid, the highest contents means were found with thrionine (105.442 mg/100g f.w) and glutamic (144.803 mg/100g f.w). Both high virulent isolates 5 and 6 contained the high amounts of Aspartic (64.810 and 136.821 mg/100g f.w respectively) and Glutamic (218.626 and 294.383 mg/100g f.w respectively) . The least amounts of free amino acids in hyphae of all isolates were proline, Cystine, Lucine and Phenylalanine. The distribution of free amino acids concentrations was varied between the different isolats and does not follow specific trend. Such data indicate that virulence of certain fungal isolates could be related to the amount of some total amino acids rather than free amino acids.