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To develop a weed control system for birdsfoot trefoil (Lotus corniculatus L.) utilizing an effective, inexpensive, and relatively safe herbicide, 2,4‐D, a recurrent selection program was undertaken to breed a strain of trefoil tolerant to this herbicide. We believe that this is the first report of the successful use of recurrent selection to develop herbicide tolerance.A series of tests established that five cycles of field selection had been effective in developing a strain substantially more tolerant to 2,4‐D than commonly used trefoil cultivars. After 2,4‐D treatment, green weight of the lowest yielding progeny line of the tolerant strain was five times that of ‘Viking.’ Survival percentage of the resistant strain was significantly higher than Viking, ‘Empire,’ ‘Mansfield,’ ‘Granger,’ and ‘Tana.’ Fresh and dry weight, plant N composition, and surface wax accumulation were significantly less affected by 2,4‐D in the tolerant strain. Evidence is presented that the 2,4‐D tolerant strain is resistant to the 2,4‐D homologs as well as the parent compound. It was suggested that evaluation of early seedling growth during exposure to herbicides in petri dish culture may prove to be both an effective and efficient screening device in breeding programs to develop tolerance to specific herbicides.

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