Evaluating the effect of increasing salinity on the growth of root rot pathogens of common bean (phaseolus vulgaris l.)
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Abstract
Common bean (Phaseolus vulgaris L.) is the most important food legume valued for human consumption worldwide. It provides an important supply of dietary calories, vitamins, minerals, and contains as much as 30% protein for its seed size. It is also favored as a sustainable crop due to its ability to fix atmospheric nitrogen. Abiotic and biotic stress factors are major constraints to common bean production. Among the abiotic stress factors, soil salinity is the most devastating in terms of yield loss. Soil salinity is on the rise and it affects nodulation and crop growth, which result in yield losses. There are many contributors to soil salinity including natural weathering and human interventions. Biotic stress factors include a variety of pathogens causing diseases including root rots. The most prevalent root rot pathogens of common beans are Fusarium solani and Rhizoctonia solani where they can reduce yield as much as 100%. In the field, plants are confronted with a combination of biotic and abiotic factors that can affect their growth and productivity. However, studies on the combined effects of these factors on common bean are very limited and interactions between salinity and root rot pathogens and its overall effect on common bean are unavailable. Therefore, this study was set out to understand this gap using methods to evaluate the potential effect of increased salinity on fungal development including an assessment of radial mycelial growth, fungal biomass, and spore germination in-vitro using solid and liquid culture media amended with sodium chloride (NaCl). Severity of rots on common bean roots were also evaluated under increasing salt stress. Significant differences in mycelial growth for both pathogens was recorded. Dry fungal biomass production in liquid media was found to be significantly different in the NaCl-amended media for both pathogens compared to the non-amended control. Spore germination of F. solani was also negatively affected by the presence of NaCl in culture media. In the growth chamber experiments, the disease severity of both root rots was found to be significantly higher in the presence of the NaCl.