Sclerotium rolfsii is one of the important pathogens which attack common bean plants causing serious damages and unexpected losses in yield. Effect of three amendments of no environmental risk i.e. paclobutrazol (PBZ), sulphated canola oil (sulphex) and humic acid on improving nutritional status of plant and reducing the invasion of common beans by Sclorotium rolfsii and hence increasing the pod yield were studied through a field experiment conducted for two successive years. Investigating the bio-defense mechanisms against infection with S. rolfsii in comparison with the effect of the fungicide Vitavax-thiram on the plants infected with Sclorotium rolfsii was also a matter of concern. The percentage of plant survival and pod yield increased significantly due to application of the amendments whose effects were significantly higher in the second growing season than in the first one. Significant increases in the uptake of N and P occurred due to these amendments. The uptake of Cu and Zn in the first growing season exceeded significantly the corresponding ones in the second growing season. PBZ stimulated the activity of chitinase enzymes as a defense mechanism against invasion of S. rolfsii, humic acid stimulated the activity of peroxidase enzymes and sulphex increased the activities of chitinase, peroxidase and polyphenol oxidase enzymes. Therefore, humic acid and PBZ are recommended for inducing phytoresistance of common bean grown in soil infected with S. rolfsii and improving its nutritional status without causing any environmental hazards. |
