Date of Award

5-2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Plant and Environmental Science

Advisor

Riley, Melissa B.

Committee Member

Norsworthy , Jason K.

Committee Member

Knap , Halina T.

Committee Member

Reddy , Krishna N.

Abstract

Wild radish ( L.), a facultative winter annual is a troublesome weed in small grain crops of the Southeastern United States. Besides being a weed, it may also be used as a cover crop for weed management due to its production of glucosinolates. Studies were conducted to evaluate the biology and ecology of wild radish as well as its glucosinolate production and its weed management possibilities.
Wild radish emerging in fall months formed a rosette of leaves which aided its winter survival. Plants emerging from December through March that did not form a rosette had minimal survival. Wild radish life cycle ranged from 43.5 to 230.5 days. Plants emerging in the fall had greater biomass and seed production compared to ones emerging in summer months. Developmental phases most influenced by the emergence date were emergence to bolting and bolting to flowering. Phenological development phases, except for flowering to silique production, were dependent on both temperature and photoperiod.
Wild radish seeds at maturation exhibited lower germination compared to seeds after-ripened in the field for 3 to 6 months. Temperatures of 5 to 15 C were required for germination. Germination was greater at fluctuating temperatures compared to constant temperatures. Burial of seeds (10-cm depth) decreased germination with red light increasing germination at 6 mo after retrieval from soil, indicating a phytochrome effect.
Five glucosinolates - glucoerucin, glucotropaeolin, glucoraphenin, glucobrassicin, and gluconasturtin were present in plant parts ranging from cotyledon to flowering stage. The highest concentration of total glucosinolates was present at the flowering stage. Glucoraphenin and glucoerucin were the predominant glucosinolates among different accessions of wild radish. Accessions from Florida and Mississippi had the greatest total glucosinolate concentration. Glucosinolates that hydrolyze to form isothiocyanates, which inhibit seed germination, comprised greater than 80% of the total glucosinolates. Wild radish cover crop alone provided good early season but not season long weed control. Wild radish in conjunction with half rates of atrazine plus S-metolachlor provided season-long control of Florida pusley, large crabgrass, spreading dayflower, and ivyleaf morningglory without affecting sweet corn yields, ultimately resulting in less herbicides required for acceptable weed control.

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