COMPARISON OF INOCULATION METHODS FOR SELECTION OF SOYBEAN GERMPLASM RESISTANT TO Phytophthora sojae (KAUFM. & GERD.)

Abstract

Phytophthora sojae Kaufm. & Gerd., the causal agent of root and stem rot of soybeans (Glycine max L), is considered one of the most limiting pathogens of the crop in Colombia. In this study, three inoculation methods of P. sojae based on mycelium and oospores (200-400 CFU mL^-1) as inoculum source were compared, with the aim of validating an efficient inoculation method for massive selection of soybean germplasm for its response to pathogen inoculation under mesh house conditions. Twelve treatments were evaluated in a randomized complete block design with factorial arrangement (3 × 2 × 2): three inoculation methods (injection, toothpicks and agar discs), two inoculation variants (with and without inoculum) and two varieties (Williams and Corpoica Orinoquía 3) with three replications. Each experimental unit comprised 10 to 15 seedlings. Considering the variables analyzed in this study (incubation period in days, percentage of mortality and time invested in min for the inoculation of 10 seedlings), it was observed that treatments based on toothpicks colonized with P. sojae caused 96.67 % mortality of seedlings in an incubation period of 8.08 days on average; they also presented the highest efficiency in the inoculation of soybean germplasm on a large scale, characterized by their practicality during the inoculation process. Results allowed the validation of the method of colonized toothpicks and its recommendation to be implemented in the AGROSAVIA soybean breeding program in Colombia.