الفهرس 
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Abstract
The responses of soybean cv. Crowford and sunflower cv. Miak, susceptible to infection by the charcoal rot pathogen Al. phaseolina and the Fusarium root rot pathogenic fungus F. solani f sp. phaseoli, in pot studies in the greenhouse were determined. Diseases symptoms at various stages of plant development were evaluated using morphological and histological approaches. Hence, the individual pathogenic characteristics of these two fungi were firstly demonstrated on the soybean and the sunflower plants using excised organs (hypocotyls) of the plants under environmental controlled conditions. Secondly, the pathogenicity was also employed to the seeds which were infected separately with each of the pathogens of concern, by applying its inoculum incorporation with the soil, under greenhouse condition. That methodology is important in demonstrating and clarifying pathogenicity in particular at the various stages of plant development. Both fungi caused a diversity of symptoms on both tested plants. Both fungi were considered a potential causal agents of blight as well as root and foot-rot of the infected plants, whether at the seedling stage, the vegetation stage or even at older stages (flowering and fruiting).
The pathogenic types of both fungi demonstrated marked effects on the health and physiology of the plants, wilt was also one of the most common among the other symptoms. A comparison of soybean and sunflower plants indicated that both fungi, separately, have marked effects on the health and physiology of the plants resulting in losses in seed yield. Definitive histological studies of infection characteristics of these fungi by light microscopy are lacking in this study. The bacterial antagonist B. subtilis and T. harzianum were all tested under greenhouse conditions. The other biocontrol agents used included the two selected isolates of streptomyces, isolate No. 112 and isolate No. 729 which resembled the species S. roseodiasticus and olivaceiscleroticus, respectively. These were effective as the fungal biocontrol agents. The isolates collection isolated in this study was described as new. The isolation and characterization of the two isolates of streptomyces spp. used were achieved for the first time in this study.
Control efficiency of the antagonistic effectiveness of the tested biocontrol(s) varied slightly with all of the microorganisms used and even between the two isolates of Streptomyces . Slight differences in reducing diseases severity and rating among them was demonstrated in this study, i.e., induced disease control by close levels were achieved against the charcoal root rot of soybean and sunflower and also against the Fusarium root rot of both plants. The latter disease was also considerably decreased compared with controls. The reduction was followed by a moderate yield increase. Differences between biocontrol treatments were not significant. Moreover, all treatments in soybean and sunflower resulted in an earlier development of pods of soybean and heads of sunflower. Decreasing levels of susceptibility, in cultivar of soybean and sunflower plants normally susceptible to M. phaseolina and F. solani f sp. phaseoli ,with each of the biocontrol used was apparent. Disease severity in either cv. Crowford of soybean or cv. Miak of sunflower resulted in limited to extensive pale flecking damage to the root and brownish necrotic hypocotyl lesions in addition to a limited type of symptoms on the leaves which was also apparent. At the seedling stage, in particular, a pale rotting of primary root was evident which slightly progressed into the hypocotyl. Only with Macrophomina pathogen that the rotting was restricted to the lower hypocotyl and primary root. At later stages of plant development, the normal susceptible diseases rating caused by the two pathogens was apparently altered. Plant growth promotion in soybean and sunflower were observed. High yield levels was evident based on the various plant growth parameters which have been observed. It was demonstrated that this phenomenon was accompanied with decreasing disease severity and rating in all of the Macrophomina or Fusarium - soybean or sunflower interaction systems which were involved: treated plants, biocontrol-infected plants, non treated (susceptible) infected plants, and the controls (biocontrol non treated- non infected plants).