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United States Department of Agriculture

Agricultural Research Service

Title: Chromosome Doubling Via Injection of Colchicine in Ba-Pretreated Daylilly (Hemerocallis SPP.)

Authors
item Sakhanokho, Hamidou
item Cheatham, Christopher
item Pounders, Cecil

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2003
Publication Date: March 1, 2004
Citation: Sakhanokho, H.F., Cheatham, C.L., Pounders Jr, C.T. 2004. Chromosome doubling via injection of colchicine in ba-pretreated daylilly (hemerocallis spp.). Meeting Abstract. March: 48-51

Technical Abstract: Economically, the daylily (Hemerocallis spp) is one the most important ornamental plant. In nature, the daylily species are mostly diploid (2n = 22), with the exception of some triploids which are generally sterile as pod parents (Tomkins et al., 2001). Tetraploid daylily cultivars are the results of doubling the basic chromosome number by breeders through chemical treatments, such as colchicine treatment. Cytokinins, including 6-benzylaminopurine (BA), belong to a class of plant hormones that promote cell division, meristem differentiation, chloroplast development, and root and leaf formation. Conversion of diploid daylily varieties into tetraploid cultivars is sought because the latter generally are heralded as having larger plants and flowers, better flower substance, and more vigorous vegetative leaves and stems. Until recently, daylily was considered for the most part a disease free plant. However, in August 2000, the daylily rust (Fig. 1 & 2), caused by the fungal pathogen Puccinia hemerocallidis, reached the southeastern United States, and by late 2001, it has was identified in 30 states (American Hemerocallis Society, 2002). The genetic diversity among modern daylily tetraploid cultivars is rapidly decreasing because of the focus put on only a limited tetraploid genotypes (Tomkins et al., 2001). Therefore, there is a need for expanding the germplasm pool through the conversion of more diploid genotypes into tetraploids. However, even though chromosome doubling through colchicine treatment has been around for decades, the technique is still considered "an art rather than science". Therefore, it is necessary to develop a dependable conversion technique that can be routinely used for chromosome doubling of any or most daylily species. The objcectives of the current study are to develop an efficient and dependable daylily conversion method, to convert a susceptible and a resistant diploid cultivar into tetraploid cultivar and to use the converted tetraploids in our breeding program aimed at elucidating the resistance gene (s) to Puccinia hemerocallidis. Preliminary results of the study will be presented.

Last Modified: 10/22/2014
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