Characterization of Dickeya zeae Causing Bacterial Stalk Rot of Maize and Advancing Efficient Inoculation Methods and Susceptible Check for Germplasm Screening

Maize is a staple food in many regions and a vital agricultural commodity that supports diverse industries and providing essential carbohydrates, proteins, vitamins, and minerals, make it a critical component of food security worldwide. Bacterial stalk rot (BSR) caused by Dickeya zeae is considered the most destructive disease of maize widespread in tropical, subtropical and temperate region of the world. This bacterium has wide host range causing soft rot which make it difficult to manage the bacterium. Cultural and biological control approaches are ineffective, and no effective chemicals are available for the management of the disease. Therefore, identification and development of resistant cultivars could be an appropriate approach. For development of resistance in plant, identification of resistant source is pre-requisite. The present study was conducted for identification of susceptible genotypes and effective artificial inoculation methods to create a higher disease pressure under suitable environmental conditions which could be utilized for germplasm screening. Under glasshouse conditions, syringe inoculation was found to be the most appropriate method; therefore, it was used for screening of ten maize genotypes against BSR. Out of the 10 genotypes screened against BSR in the glasshouse, Chakrata Local was found to be the most susceptible and PSM 6 was most resistant. Under field conditions, seven inoculation methods were further evaluated for their efficacy in creating higher disease pressure in Chakrata Local and PSM 6. Syringe inoculation was found to be most consistent and effective method of inoculation under both glasshouse and field conditions followed by toothpick inoculation. The techniques identified in the present investigation are of considerable importance for development of artificial epiphytic conditions in the field for screening of appropriate resistant sources which could be used both in the farmers’ field and breeding programs.