Genetic Parameters and Selection Responses for Important Breeding Traits in Liquidambar formosana Based on a Provenance-Family Trial

Liquidambar formosana is a multipurpose tree species native to China. There has been increasing interest in L. formosana due to its leaves being rich in shikimic acid, which plays a key role in the synthesis of the antiviral drug oseltamivir phosphate. Here, shikimic acid content (SAC) and other breeding traits, including tree height (HT), diameter at breast height (DBH), height to crown base (HCB), individual tree volume (VOL), leaf color (LC) and stem straightness degree (SSD), for 387 families of 19 provenances were evaluated in a provenance-family trial of L. formosana to estimate genetic parameters and reveal geographical variation patterns and, ultimately, screen out superior provenances and families. Differences among provenances and families were significant for all tested traits, indicating a high potential for selective breeding. Broad-sense heritabilities of provenance (h(p)(2) p = 0.19-0.57) and family (h(f)(2) = 0.16-0.31) were moderate for most traits. Moderate to strong genetic correlations were found among HT, DBH, VOL, HCB and LC (r(A) = 0.339-0.982), while adverse correlations (r(A) = 0.494 to 0.816) were observed between SAC and growth traits. All target traits, excluding SSD, exhibited clinal variation in response to latitudinal gradients, and a clustering heatmap divided the 19 provenances into three groups. For single-trait selection, SAC persistently had the highest genetic gains (85.14%-163.57%). A weighted index based on breeding values was used to concomitantly improve SAC, HT and DBH. At a selection rate of 25%, the genetic gains at the provenance and family levels for SAC were 36.42% and 73.52%, and those for core growth traits ranged from 2.29% to 3.49% and 4.05% to 4.47%, respectively. As far as we know, this is the first study in L. formosana to explore the inheritance of SAC and its correlations with other traditional breeding traits. The genetic parameter estimations contribute to a better understanding of the genetic basis of SAC, and the superior provenances and families obtained lay a material foundation for the development of new varieties rich in shikimic acid, thereby promoting the in-depth exploitation and utilization of germplasm resources of L. formosana.