The role of plant size in the selection of glyphosate resistance in Sorghum halepense

VILA-AIUB, MARTIN; CASAS, CECILIA; GUNDEL, PEDRO E

PEST MANAGEMENT SCIENCE

JOHN WILEY & SONS LTD

Año: 2018

1526-498X

BACKGROUND: The effect of plant size (seedlings versus young plants versus adult plants) on the phenotypic level of glyphosate resistance and selection intensity (SI) in Sorghum halepense with and without a reduced glyphosate translocation resistancemechanism was evaluated. RESULTS: Resistance parameters [the 50% lethal dose (LD50) and the dose required to cause a 50% reduction in plant growth (GR50)] in adult plantswere notably higher than in seedlingsregardless of the resistance status.However, under similar plant size increases, populations comprised of glyphosate-resistant (R) individuals showed higher survival and growth when glyphosate treated comparedwith glyphosate-susceptible (S) plants.An increase in SIwas always evidentwith increasing glyphosate doses. However, the rate of increase in SI was higher under glyphosate selection of young R and S plants, followed by seedlings and adult R and S plants. However, in conditions of R seedlings coexisting with adult S plants under glyphosate treatment (1000?4000 g ha−1), selection against glyphosate resistance was observed. CONCLUSION: Any increase in size fromthe seedling stage of R plants translates into an amplification of resistance. Depending on the particular size combinations of spatially coexisting R and S plants, selection for glyphosate resistance may be faster, slower or even not evident.