Effect of growing media on greenhouse production of mini-tuber (P-13)

Powdery scab is caused by the fungal-like pathogen, Spongospora subterranea f. sp. subterranea (Sss), and can lead to significant damage to potato tubers, impacting both seed and commercial production. In addition to causing tuber lesions, Sss may also cause root galls, and vectors the potato mop-top virus (PMTV). Recent research from Colorado State University detected Sss in some commercial peat-based potting mixes, which could lead to contamination of greenhouse-grown mini tubers. Once Sss is present in a field, it can persist for over 10 years, continuously causing damage. Traditionally, greenhouse producers use soil alternatives to minimize the contamination risks through soil-borne pathogens. This study examined five alternative growing media, including coconut coir, vermiculite, sand, perlite, and Promix BX (a common peat mossed-based mix). The coconut coir produced a higher quantity and larger sized tubers than the alternatives and posed a significantly lower risk of Sss contamination. Moreover, the coconut coir media had the highest water retention in this study, suggesting up to 50% more water use efficiency. This research finds coconut coir as a promising, safer alternative for greenhouse seedling tuber and minituber production, enhancing yield, and mitigating disease risks.