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Title: Bud emergence and shoot growth from mature citrus nodal stem segments

Author
item Hert, Mizuri
item Evens, Terence
item McCollum, Thomas
item Niedz, Randall

Submitted to: Plant Cell Tissue and Organ Culture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2010
Publication Date: 7/1/2011
Citation: Hert, M.M., Evens, T.J., McCollum, T.G., Niedz, R.P. 2011. Bud emergence and shoot growth from mature citrus nodal stem segments. Plant Cell Tissue And Organ Culture. 106(1):81-91.

Interpretive Summary: Plant tissue culture is the science of growing plant cells, tissues or organs isolated on artificial media. Plant propagation via tissue culture is termed micropropagation. Some advantages of micropropagation include 1) high production rates – thousands/millions of plantlets produced vs. conventional propagation; 2) propagation of plants where conventional propagation is difficult, uneconomical, or impossible (e.g., plants that produce low quantities of seeds, are seed sterile, or produce seeds that are not viable or cannot be stored); and 3) the in vitro environment protects plants from external pests and diseases. We have identified compounds and conditions that improve the growth of shoots of mature tissue buds from citrus trees. Culturing mature tissue is required for in vitro conservation where valuable plant varieties and species are maintained in vitro to protect from loss in the field by pests, diseases, or environmental stresses. In vitro culture of mature tissue would also be useful for providing a source of clean plant material for in vitro experimentation such as genetic engineering since plants derived from mature tissue will flower in less than two years vs. 6-10 years from seedling trees.

Technical Abstract: Bud emergence and shoot growth from adult phase citrus nodal cultures were studied using Citrus mitis (calamondin), Citrus paradisi (grapefruit), and Citrus sinensis (sweet orange). The effects of 6-benzylaminopurine (BA), indole 3-acetic acid (IAA), and citrus type on shoot quality and growth from mature bud explants from greenhouse grown trees were determined using a 2-component mixture-amount x citrus type experiment. BA increased shoot number and IAA improved shoot growth. The best shoot quality (fewer shoots but good growth) was obtained with 1 µM IAA for calamondin, 15.5 µM IAA for sweet orange, and 30 µM IAA for grapefruit. However, grapefruit exhibited substantial leaf abscission. Five factors (AgNO3, silver thiosulphate (STS), CaNO3, gelling, or salt concentration) were screened individually for their efficacy in reducing leaf abscission. Five factors (AgNO3, gelling, salt concentration, plant growth regulator, and venting) were investigated to identify potential combinations for reducing leaf abscission. The treatments identified as most effective in minimizing leaf drop, promoting shoot growth, and maximizing bud emergence for grapefruit was 11.78 µM AgNO3, Gelrite, 1X MS salt, 30 µM IAA, and vented.