Disinfection and in vitro viability of arbuscular mycorrhizae associated with potato (Solanum tuberosum L.) for the scalability of high-purity native inoculants

Abstract

Mycorrhizal bioprospecting is the search, identification, and evaluation of mycorrhizal fungi with superior functional traits for their use as biological resources in agriculture or environmental restoration. The application of spore disinfection and viability methodologies enhances bioprospecting by enabling the development of new mycorrhiza production protocols aimed at improving symbiosis and increasing infective propagules (spores, hyphae, and root fragments). The objective of this study was to develop a protocol to evaluate the response to disinfection and in vitro germination of native mycorrhizae isolated from potato plants (Solanum tuberosum L.). Mycorrhizal samples were collected from two farms in the department of Estelí, in northern Nicaragua, cultivated with potato crops aged between 35 and 50 days, corresponding to the cultivars Picasso, Panamera, Nemphis, and Sylvana. Population density and relative abundance of mycorrhizal spores in soil samples were quantified, and the genera were identified using morphological keys. Subsequently, the colonization of typical fungal structures such as hyphae, vesicles, and arbuscules in roots was quantified. Finally, the most effective methodology for mycorrhizal spore disinfection was determined, and the most suitable spore germination media were defined by incubating spores in different culture media at 25 °C for seven days. The identified genera corresponded to Glomus spp., Scutellospora spp., and Gigaspora spp. The Panamera cultivar exhibited the highest density of viable spores (4.2 spores per 10 g of soil), showing significant differences compared with the Sylvana cultivar. The genus Glomus spp. was the most abundant (76%) in the Picasso cultivar. The highest value of hyphal colonization was observed in the Picasso cultivar (15.27). No significant differences were recorded in the quantification of arbuscule and vesicle structures. Three spore disinfection methodologies were evaluated, of which methodology 3, based on chloramine T combined with streptomycin and gentamicin, achieved 70% of Glomus spp. spores free of fungal and bacterial contaminants when grown in vitro on 50% MS medium. Spore germination occurred exclusively in the minimal medium, with five spores germinated. The percentage of arbuscular mycorrhizae in potato roots and soil was very low, indicating that poor crop management practices involving high chemical inputs not only reduce the quantity of spores present and the number of mycorrhizal species, but also compromise their viability to establish symbiosis with the plant.