Xiao-Lu Chen1,3*, Dahanayake Nilanthi2, Yue-Sheng Yang3*, Dong-Liang Li3,4, Jun-Jie Zhang3, Qing-Ling Li3, Rong Chen3, Hong Wu3
1 Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences /Key Laboratory of Crop Gene Resources and Germplasm Enhancement in Southern China, Ministry of Agriculture, Danzhou, Hainan, China
2Department of Agricultural Biology, Faculty of Agriculture, University of Ruhuna, Matara, Sri Lanka
3 College of Life Sciences, South China Agricultural University, Guangzhou, Guangdong, China
4 Institute of Tropical Horticulture Research, Hainan Academy of Agricultural Science, Haikou, Hainan, China
Abstrsact
Leaf, petiole, and root explants from in vitro maintained triploid purple coneflower plantlets were treated with
120 mg·L-1colchicine for the induction of hexaploid plants. Best result for induction of hexaploid was obtained
by treating the triploid root explants with 120 mg·L-1 colchicine for 25 days. Regeneration of adventitious buds
from the triploid root explants on Murashige and Skoog (MS) medium with 6-Benzyladenine (BA) and Naphthalene
acetic acid (NAA) after the colchicine treatment persisted for a time longer than from those untreated.
Only slow-growing plantlets in a same genotype and treated population were selected and detected to increase
the screening efficiency as well as save time and efforts. Chromosome counting confirmed that most early-regenerating
and fast-growing buds were triploid, while most late-regenerating and slow-growing buds were hexaploid, screening only
those slow-growing regenerated plantlets could increase effectively the hexaploid. In the present study, screening efficiency
increased from 21% (detected all plantlets) to 53% (detected only the slow-growing plantlets). On the other hand, hexaploid
plants had much larger stomata and more stomatal guard cell chloroplasts. The stomatal guard cell chloroplast number in hexaploid
plants has a good linear relationship with those in the diploid, triploid, and the tetraploid progenitors. Results indicate that
the colchicine-induced hexaploid could be induced and screened out with high efficiency, making this process worth further exploring in other species as well.
Key words: chloroplast, Echinacea purpurea, hexaploid, polyploidy, screening, stomata
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