SEEDLING AND ADULT PLANT RESISTANCE TO Uromyces viciae-fabae (Pers.) J. Schröt. IN MEXICAN FABA BEAN (Vicia faba L.) GENOTYPES

Resumen

Faba bean rust (Vicia faba L.) is a globally significant disease caused by Uromyces viciae-fabae (Pers.) J. Schröt, resulting in yield losses of up to 70 %. Genetic resistance, whether specific or non-specific, is viable for reducing losses caused by this fungus. In faba bean, genotypes with specific resistance to U. viciae-fabae have been found, although most genotypes allow for some levels of pathogen reproduction. Therefore, the objective was to evaluate the resistance to U. viciae-fabae in faba bean lines at the seedling and adult plant stages. Thirty faba bean genotypes were examined as part of two breeding initiatives at Postgraduate College and the Agricultural, Aquaculture, and Forestry Research and Training Institute of the State of Mexico. Adult plants were evaluated in the field at two locations: 1) Palmillas, Texcaltitlán, State of Mexico, and 2) Postgraduate College Montecillo Campus, Texcoco, State of Mexico. A two-factor factorial model was used in the design, which included a generalized randomized block design and four replicates. The variables evaluated were the percentage of disease severity, final severity, and grain yield. Seedlings were inoculated with a concentration of 3 × 10⁶ urediniospores mL^-1, incubated in a growth chamber at 18 ± 2 °C and 100 % relative humidity for 24 h, and transferred to a temperature-controlled greenhouse at 18 ± 2 °C. The variables evaluated included the number of pustules per leaf, the severity percentage, pustule size, latency period (LP1, LP50, and LP100), and the type of infection. Approximately 95 % of the lines tested in seedlings were susceptible to faba bean rust, with line 20CP showing moderate resistance. Incomplete non-hypersensitive resistance was identified in the bean-U. viciae-fabae pathosystem.