Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Plant Pathology and Physiology

Common bean (Phaseolus vulgaris L.) is considered a very common vegetable crop in many countries worldwide. Damping-off disease during early stages of bean growth, causes great losses for growers. Growers use to use highly toxic chemical fungicides to protect their investment and get rid of damping-off problem. Using these toxic chemicals led to rejection of exported shipment. The present work offers biological control as a substitute for the toxic chemicals. Different bioagents were used (Trichoderma spp., Bacillus subtilis, B. megaterium, Pseudomonas fluorescens and Streptomyces sp.).Three mixtures consist of Trichoderma spp. isolates (T1+T2) or mixture of B. subtilis isolates (B1+B2) or combination between T. harzianum isolate plus B. subtilis isolate (B2+T2) were used to illustrate their effect on plant protection against damping-off and also their side effect on beneficial bacterium Rhizobium phaseoli. A mixture consists of B. subtilis+T. harzianum (B2+T2) either in form of powder or suspension showed the highest effect in disease control and green yield compared with control treatment or effect of other treatments. Using mixture of (B2+T2) led to clear increase in free phenols, total phenols, reduced sugars, amount of chlorophyll in addition to percentage of protein. The highest synergistic effect was recorded when Rh. phaseoli was used in combination with mixture (B2+T2). Data obtained indicate that all mixtures of biocontrol agents in combination with Rh. phaseoli led to increase number of rhizobium nodules, fresh and dry weight of roots and shoots, in addition to increase in number of pods/plant, yield/plant and weight of 100 pods. The highest increases in these components (free phenol, total phenol, reduced sugar, chlorophyll and protein) were noticed when Rh. phaseoli was used in presence of (B2+T2) mixture compared with any other treatment

Issued also as CD