Integrated Control of Pathogens Associated with Bean Seeds

Abstract, Journal of American Science, 2018

The associated fungi of bean seeds were purified and identified as Alternaria alternata, Aspergillus spp., Botrytis cinerea, Fusarium solani, Macrophomina phaseolina, Penicillium sp., Rhizoctonia solani, Sclerotinia sclerotiorum, Trichoderma viride and Verticillium sp. Four tested fungi (R. solani, M. phaseolina, F. solani, and S. sclerotiorum) were proved to be pathogenic producing different degrees of pre-emergence (PRD), and postemergence (PTD) damping-off and root rot symptoms on bean cultivars: Contender, Narina, Bolista and Giza-6. The most virulent isolates inducing PRD were F. solani, M. phasiolina and R. solani whereas S. sclerotiorum was the least virulent. Moreover, the highest levels of PTD were obtained with S. sclerotiorum, F. solani, and R. solani, whereas M. phasiolina was the least virulent. Bolista cultivar was the most compatible with PRD and PTD in all tested pathogenic fungi, whereas Giza-6 showed the lowest compatibility. The highest percentage of root-rot infection were obtained in Bolista cultivar with the tested fungi ranged from (70-80 %) and Narina (70-75 %), while the least infection was obtained in Giza-6 (55-60 %). Plant oils (Cinnamon, Clove, Spearmint and Lemon) were tested for their antifungal activities against the four tested pathogenic fungi in vitro and significantly reduced in their radial growth. Spearmint oil exhibited the highest antagonistic effect to the tested fungi followed by Clove and Cinnamon oils, while the least effect was Lemon oil compared with control. Hyphal growth of R. solani and S. sclerotiorum was completely inhibited with 100 % and 75 % conc. with Spearmint oil, while R. solani was completely inhibited by 100 % conc. with Cinnamon oil. In addition, the biological agents Trichoderma viride, T. harzianum, T. koningii and Bacillus subtilis were used in vitro to test their effectiveness against the four tested pathogenic fungi. In vitro experiment showed that all biological agents significantly reduced the linear growth of fungi. T. harzianum showed highly antagonistic effect, the growth reduction ranged from (75.6 to 77.8 %), while B. subtilis was the least, growth reduction ranged from (56.7 to 65.6 %) to the tested pathogenic fungi. Pot experiment In general, The tested treatments were evaluated in a pot experiments and resulted in significant effects on controlling pre- and post-emergence damping-off as well as root-rot diseases of bean caused by R. solani, M. phaseoilina, F. solani, and S. sclerotiorum when compared to the untreated control. In addition, treatment with T. harzianum was superior to the rest of the other treatments in controlling such studied diseases.