Planting Substrate Mixture Impacts Yield and Size of Nuclear Potato Tubers

Abstract

Potato (Solanum tuberosum) is a vegetatively propagated crop for which certification programs seek to ensure cleanliness of seed supply and true-to-type cultivars. Seed potato planting stocks start from micropropagated plantlets transplanted to a greenhouse for nuclear tuber production. Tubers are then grown for multiple generations in the field before use in commercial ware potato production. Growers consider factors such as crop genetics and management to ensure productivity and quality. However, the impact of the media in which micropropagated potato plantlets are grown and the host plant’s associated bacterial communities are often overlooked. We hypothesized that tubers from high yielding plants will have higher endophytic bacteria diversity, and these will continue to produce high yield in the subsequent field season. In this study, we conducted two sequential experiments involving potato plantlets of two cultivars (‘Russet Norkotah’ and ‘Silverton Russet’). The first experiment was conducted in a greenhouse, where the plantlets were grown in four different planting substrates: peat-based media (a former standard now discontinued due to potential for pathogen contamination), and three alternate substrates (Perlite, 2:1 perlite and calcined clay, and 2:1 perlite and rice hulls). Dry aboveground biomass, tuber set, and yield at harvest were measured. The tubers harvested from the greenhouse were then used in a subsequent field experiment. In this second experiment, we measured canopy coverage, total tuber yield and tuber set. For both cultivars in both the greenhouse and field experiment, 2:1 perlite and calcined clay had similar high nuclear tuber yield to plants grown in peat-based media. In the field experiment, for both cultivars, larger planted tuber size resulted in increased measurements across all tuber metrics. Therefore the results indicated that 2:1 perlite and calcined clay mixture has the potential as a suitable alternative substrate for micropropagated potato plantlets. Alpha diversity indices revealed no significant differences in tuber bacterial richness and diversity between substrates and experiment repetitions. Beta diversity analyses demonstrated that experiment repetition had the strongest effect on the composition of the bacterial communities on tubers. This research highlights the need for greater understanding of planting substrate impact on potato microbiome, nuclear tuber productivity and product quality, which may lead to improved early generation seed potato production practices.