EST-SSRs development and paternity analysis for Liriodendron spp

Liriodendron are ideal plants for research on mating system, systemic evolution and population genetics. Here we report the development and application of a set of simple sequence repeat (SSR) markers derived from expressed sequence tags (ESTs) of L. tulipifera. In total, 176 primer pairs were developed and yielded 132 EST-SSR markers that amplified clear SSR bands with genomic DNA of L. tulipifera. Transferability of these EST-SSR markers to related species and genera was further examined. Twelve highly informative loci screened from 132 EST-SSR markers were applied to explore the effective pollen dispersal patterns and male reproductive success of Liriodendron. A provenance trial population of Liriodendron comprised 12 L. chinense (Hemsl.) Sarg provenances and 5 L. tulipifera provenances. The four maternal trees were randomly sampled as tested maternal trees in the population. Paternities of 220 open-pollination progenies from 4 maternal trees above were potentially identified by means of paternity analysis, of which 138 progenies (accounting for 62.7%) were assigned to 49 male parents at the 95% confidence level. The cumulative exclusion probability of 12 EST-SSR loci was 98.5%. The average effective pollen dispersal distance of pollen donors ranged from 15 to 35 m, with the maximum dispersal distance of 77 m. There were obvious male reproductive success differences among individuals, ranging from 0 to 10.9%. The cumulative male reproductive success of individuals within 35 m radius around the known maternal trees reached 51.4%. Diversiform mating patterns, including selfing, intra-species mating and interspecies mating, coexisted in the occasion of open-pollination in Liriodendron.