Inheritance of evolved glyphosate resistance in Lolium rigidum (Gaud.)

Resistance to the non-selective herbicide, glyphosate, has evolved recently in several populations of Lolium rigidum (Gaud.). Based upon the observed pattern of inheritance, glyphosate resistant and susceptible populations ar e most probably homozygous for glyphosate resistance and susceptibility res pectively. When these populations were crossed and the F-1 progeny treated with glyphosate, the dose response behavior was intermediate to that of the parental populations. This observation, coupled with an absence of a diffe rence between reciprocal F-1 populations, suggests that glyphosate resistan ce is inherited as an incompletely dominant nuclear-encoded trait. The segr egation of resistance in F-1 x S backcrosses suggests that the major part o f the observed resistance is conferred by a single gene, although at low gl yphosate treatments other genes may also contribute to plant survival. It a ppears from this study that a single nuclear gene confers resistance to gly phosate in one population of L. rigidum.