Wednesday, November 15, 2006 - 9:45 AM
259-5

Changes in Bermudagrass Carotenoid Composition Following Mesotrione Application.

J. Scott McElroy1, Dean A. Kopsell2, and John C. Sorochan2. (1) 2431 Joe Johnson Dr, University of Tennessee-Knoxville, University of Tennessee, Plant Sciences Dept./ 252 Plant Sciences Bldg, Knoxville, TN 37996-4561, (2) University of Tennessee, Knoxville, TN 37996

Mesotrione is an indirect inhibitor of phytoene desaturase by directly inhibiting production of the cofactor plastoquinone.  Susceptible species develop whitened tissue which leads to eventual death.  However, bermudagrass (Cynodon dactylon) recovers after 21 to 28 days.  It has been previously hypothesized that essential carotenoids decrease concomitantly following inhibition of phyotene desaturase.  Research was conducted to test this hypothesis.  Bermudagrass (‘Riviera’) leaf tissue was harvested at 0, 3, 7, 14 21, 28, and 35 days after treatment with meostrione (0.26 kg ai/ha).  Bermudagrass tissue whitened up to 40% from 3 to 21 dat, but whitening disappeared after 28 DAT.  Phytoene reached detectable levels from 3 to 14 DAT, but was undetectable after 21 days.  Chlorophyll a and b, beta-carotene, lutein, neoxanthin, and violaxanthin decreased from 3 to 21 DAT, but levels increased above the 0 DAT baseline levels at 35 DAT.  Antheraxanthin and zeaxanthin quantities fluctuated erratically.  These carotenoids increased from the initial 0 DAT baseline at 3, 14, and 35 days, but concentrations decreased at 7, 21, and 28 DAT. 

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