Classification of flowering lotus cultivars in Japan, including “Ogura-ike group cultivars”, based on SSR markers

The lotus (genus Nelumbo) is classified to the sacred (N. nucifera) and American lotuses (N. lutea). Lotuses for ornamental flowers, called flowering lotuses, are recorded about 1000 cultivars in Japan, but their relationships are unclear. Especially, the origins and inter-cultivar relationships are mostly unknown for “Ogura-ike group cultivars” that were collected from the lake Ogura-ike or its reclaimed land at southern part of Kyoto Prefecture. In this study, 173 representative flowering lotus cultivars in Japan, including 94 lines of Ogura-ike group cultivars, were analyzed using 25 loci of simple sequence repeat (SSR) markers. Furthermore, a neighbor-joining phylogram was constructed based on the SSR genotypes, using total 220 lines after addition of the previously analyzed data from 47 lines. The resultant phylogram was composed of five following groups. I: a group composed of American lotuses, II: a group composed of hybrids between American and sacred lotuses, III: a group including madara-basu (lotuses with white petals irregularly fringed with purple-red spots), IV: a group including several ancient lotuses (lotuses derived from seeds excavated from ancient deposits or ruins), and V: miscellaneous group. Ogura-ike group cultivars were distributed into groups III–V, suggesting that these cultivars are derived from multiple diverse lines. In contrast, several lines of Ogura-ike group cultivars formed their own cluster, which might have been derived from closely related genotypes that grew in Ogura-ike in the past. The data in this study would provide valuable information as one of standards for classification of flowering lotus cultivars, especially for unraveling the relationships of Ogura-ike group cultivars in flowering lotuses.