Annual growth cycle observation, hybridization and forcing culture for improving the ornamental application of Paeonia lactiflora Pall. in the low-latitude regions

Authors: ZHANG, JIAPING - Zhejiang University; ZHANG, DONG - Zhejiang University; WEI, JIANFEN - Hangzhou Landscaping Incorporated; ZIAOHUA, SHI - Hangzhou Landscaping Incorporated; HUAQIAO, DING - Hangzhou Landscaping Incorporated; OIU, SHUAI - Hangzhou Landscaping Incorporated; GUO, JUAN - Hangzhou Landscaping Incorporated; LI, DANQING - Zhejiang University; ZHU, KAIYUAN - Hangzhou Landscaping Incorporated; ZHOU, JIANGHUA - Hangzhou Landscaping Incorporated; Horvath, David; XIA, YIPING - Zhejiang University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2019
Publication Date: 6/13/2019
Citation: Zhang, J., Zhang, D., Wei, J., Xiaohua, S., Huaqiao, D., Qiu, S., Guo, J., Li, D., Zhu, K., Zhou, J., Horvath, D.P., Xia, Y. 2019. Annual growth cycle observation, hybridization and forcing culture for improving the ornamental application of Paeonia lactiflora Pall. in the low-latitude regions. PLoS One. 14(6):e0218164. https://doi.org/10.1371/journal.pone.0218164.
DOI: https://doi.org/10.1371/journal.pone.0218164

Interpretive Summary: Herbaceous peony is a valuable horticultural plant in China and throughout the world. However, it cannot be grown in warmer climates because it needs to experience a period of cold temperatures to maintain flowering and vigorous growth. We examined the growth of three different peony cultivars from regions of northern and southern China and followed their ability to flower and maintain growth over several years. After confirming that pollen from the cultivar Hang Baishao was viable, we successfully bred it with the other two cultivars and determined that some flowering traits seemed to be partially transferred to the resulting offspring. We also looked for other ways to stimulate flowering of potted peony and found that treating them with known flower-inducing chemicals called gibberellic acid and 5-azacytidine did not significantly increase flowering. However, a common chemical called humic acid in combination with a minimal cold treatment induced excellent flowering. This work provides a new procedure for producing good yields of cut flowers of peony and provides a basic set of information needed for developing new cultivars of peony that can grow and flower in warmer regions of the world. Seeds from these crosses will help scientists better understand the processes by which cold treatments promote flowering in peony hybrids after shorter cold treatments.

Technical Abstract: The southward plantation of herbaceous peony (Paeonia lactiflora Pall.) to subtropical regions is a significant horticultural work in the Northern Hemisphere. However, the high temperature in winter hinders dormancy release and flowering of peony in subtropical regions. Resource introduction and hybridization could contribute to create new cultivars with high adaptability under warm winters. In this study, three representative cultivars of P. lactiflora were screened, and their annual life cycles were observed to provide information needed for hybridization. The pollen viability of ‘Hang Baishao’, a special south peony among these three cultivars, was 55.60% based on five measuring methods. Hybrid plants among three cultivars grew well but their flower buds aborted. We tested the ability of several growth regulators that impact flowering regulation of ‘Hang Baishao’ to promote an indoor cultivation strategy for improving peony as potted or cut-flower. 5-azacytidine could impact the growth to a certain degree and induce the dwarfs with mignon flowers, but did not advance the flowering time. GA3 promoted the sprouting and growth significantly, but ‘Hang Baishao’ plants withered. Chilling in 0-4' for four weeks and irrigating 300 mg/L humic acid was the best combination to hasten flowering while ensuring flowering quality. These results could contribute to increase the production and extend the range of peony to the subtropical regions with the warm winter climate.