Bacterial endophytic communities in nuclear potato tubers

Potato 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 associated bacterial communities are often overlooked. We hypothesized that the medium in which potato plantlets are grown, and the endophytic bacterial diversity found in high yielding early generation seed tubers, can have a lasting influence on potato plant productivity in subsequent field years 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 in 1 perlite and calcined clay, and 2 in 1 perlite and rice hulls. Alpha diversity indices revealed no significant differences in tuber bacterial richness and diversity between substrates and experiment repetitions. Beta diversity analyses demonstrated that harvest time 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.