Inoculation methods and conidial densities of Fusarium oxysporum f. sp. radicis lycoperici in tomato

Abstract

Fusarium oxysporum f.sp. radicis-lycopersici (Forl) is one of the most destructive necrotrophic pathogens affecting tomato crops, causing considerable field and greenhouse yield losses. The use of resistant cultivars is a safe, non-contaminating and reliable control method to eradicate or mitigate this disease. However, it is still necessary to determine the best inoculum density, sufficient to induce levels of resistance or susceptibility. In this study, inoculum concentrations of 3, 5 and 8 x 10 6 microconidia per mL of Forl were evaluated by root immersion and seed spraying in twenty tomato genotypes (Solanum spp.) in a completely randomized design. The germplasm was mainly introduced tomato species from the Genetic Resources Program of the University of California at Davis, USA. The inoculation was done by immersion of roots and by sprinkling of seeds at the time of sowing. For the inoculation by immersion of roots, tomato seedlings of 15 days emergence were used. The wounds were created in root tips then they submerged into the each conidial suspension. Finally, they transplanted into the plastic pots in a greenhouse. Regarding the inoculation by sprinkling of the seed, 20 seeds of each genotype were placed in plastic pots then sprayed with the corresponding conidial suspension. In both cases, the disease index was calculated. This allowed classifying the genotypes as resistant and susceptible. With the root immersion method all the genotypes evaluated showed susceptible. Significant differences were observed (p≤0.01) between genetic materials at different inoculum doses with the inoculation of seeds. This allowed classification of genotypes Solanum parviflorum LA 1326, Solanum chesmanii f. minor LA1401, Solanum chmielewskii LA1306, Solanum pimpinellifolium LA722, Solanum pimpinellifolium LA2184 as resistant to Forl with disease index of 3, 4, 5, 8 and 12% respectively, at a inoculum concentration of 3x10 6 microconidia per mL. These genotypes could be included in a genetic breeding program for resistance to crown and root rot caused by Forl.

First report of root rot disease on Solanum lycopersicum L. caused by Fusarium vanettenii in India

“…Ten‐day‐old cultures on PDA was used to prepare spore suspension with 10 ml of sterilized distilled water. To inoculate the fungus, thirty healthy tomato seedlings’ root tips were cut by sterilized scissor followed by dipping the wound root with spore suspension (1 × 10 6 conidia/ml) for 8 h (López‐Benítez et al., 2018). Five seedlings were inoculated with sterilized distilled water to serve as a control.…”

Monitoring for a new I3 resistance gene-breaking race of F. oxysporum f. sp. lycopersici (Fusarium wilt) in California processing tomatoes following recent widespread adoption of resistant (F3) cultivars: Challenges with race 3 and 4 differentiation methods

“…Due to these challenges, in planta-based methods continue to provide the standard for the accurate differentiation of pathogenic from nonpathogenic strains, segregation of the different formae specialis, and differentiation of Fol races (e.g., Loṕez-Benıtez et al, 2018;Cabral et al, 2020;Munawar et al, 2020;Armenta-Loṕez et al, 2021;de Oliveira et al, 2021). In planta identification methods vary in terms of plant age, inoculation method, and the duration needed for symptom development, with results in 2-12 weeks, depending on the method.…”