الفهرس 
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Abstract
Orobanche crenata is a parasitic weed which is widely distributed in the Mediterranean basin and the Middle East causing great damage to legumes especially faba bean.
The present study was conducted in order to isolate Fusarium and to screen the isolates for mycohherbicidal activity against O. crenata. A total of 2133 cfu of Fusarium were obtained from samples of young O. crenata infected stalks collected from infested fields of faba bean (Vicia faba L.) in Alkalyoubia and Alfaiyoum governorates, Egypt.
The purified isolates were checked for similarity and grouped according to their morphological characters. All the isolates were identified to the genus level and were assigned to the genus Fusarium. Among the identified isolates, F. oxysporum and F. solani were the most prevalent species.
The pathogenicity of the obtained Fusarium isolates to O. crenata was evaluated in a series of in vitro assays as follows: Phytotoxicity of the culture filtrates of the Fusarium isolates were tested against the germination of O. crenata seeds stimulated with the synthetic stimulant Nijmigen-1. Levels of inhibition in seed germination were found to vary among the tested Fusarium isolates, ten isolates showed high phytotoxicity, causing inhibition of 75-90% of O. crenata seeds and seventeen isolates showed good phytotoxicity with inhibition of values between 50 and 74%. The rest of the isolates showed moderate or low inhibition potential.
Filtrates of liquid cultures of the Fusarium isolates were also used to assess the virulence of isolates against the tubercles of O. crenata formed on faba bean roots, in this assay fourteen isolates proved to be highly pathogenic to the tubercles with virulence ranking 3 (blackening of the tubercle tissue with or without tissue wet rot), another seventeen isolates showed significant pathogenicity to the tubercles with virulence ranking 2, the rest of the tested isolates were either weakly pathogenic or non-pathogenic.
Further tests were also run on liquid culture filtrates to assess the mycotoixicity of the Fusarium isolates on the larvae of brine shrimps (Artemia salina). The majority of isolates were found to be non toxic or weakly toxic, five isolates were moderately toxic, while only two were highly toxic causing death of 80-100% of larvae.
‘Pesta’ formulations from either chlamydospores or microconidia of the five most active isolates (amended with sucrose, yeast extract or a combination of them with or without glycerol) were prepared and their efficiency in controlling O. crenata was evaluated in vivo in greenhouse trials. Parameters used for evaluation included the reduction in number of emerged shoots and in shoot dry weight of Orobanche crenata in addition to the improvement gained during these treatments in faba bean shoot and root dry weight. The two isolates of Fusarium oxysporum F1 and F2 were the most effective in controlling crenate broomrape with percentages of control reaching 75.3 and 76.5%, respectively.