Seedbank persistence, germination and early growth of glyphosate‐resistant Kochia scoparia

Abstract

Summary This study describes the seedbank persistence of glyphosate‐resistant (GR) Kochia scoparia at two sites in western Canada and examines if GRK. scoparia from western Canada and mid‐western United States (USA) differ from their susceptible counterparts in seed germination and early growth characteristics at low‐temperature regimes. Site or depth of seed burial (surface, 2.5 cm, 10 cm) did not affect seed viability over time and time to 50% and 90% loss of viability averaged 210 and 232 days respectively. Glyphosate‐resistant K. scoparia generally germinated later and had lower cumulative germination than glyphosate‐susceptible (GS) K. scoparia from Saskatchewan, Canada; and Kansas, USA; but not Colorado, USA. Similarly, time to 10% first leaf of GSK. scoparia from Saskatchewan and Kansas tended to be sooner than that of GRK. scoparia, with a greater percentage of GS vs. GR seedlings of populations from all regions having attained first leaf by the end of the experiment. The short seedbank longevity and delayed and reduced germination and time to first leaf of GRK. scoparia may potentially be exploited to maximise management efficacy through delayed preseeding weed control or alternatively by early seeding date to enhance crop competitiveness.

Dormancy, a critical trait for weed success in crop production systems

“…This pattern of directional selection became apparent for several populations of grass weeds, and also for broadleaf weeds . Weeds that succeed in these cropping systems are able to withstand or escape from the effect of pre‐sowing practices and post‐sowing herbicide applications.…”

“…Interestingly selection for traits in the population reducing seed aging rate due to environmental factors (i.e. during storage in the soil) are also selected by herbicide applications influencing seed‐bank persistence …”

“…This pattern of directional selection became apparent for several populations of grass weeds, 1,13,[28][29][30] and also for broadleaf weeds. 31,32 Weeds that succeed in these cropping systems are able to withstand or escape from the effect of pre-sowing practices and post-sowing herbicide applications. Whereas pre-sowing practices usually kill seedlings arising from early-germinating seeds belonging to the less dormant fraction of the seed-bank, herbicides applied after sowing kill those seedlings that are sensitive to the herbicide.…”

“…during storage in the soil) are also selected by herbicide applications influencing seed-bank persistence. 31,34,35 By contrast, herbicide resistance has also been associated with other changes in seed germination response, as for example, changes in the requirement of light for seed germination, that can have an ecological cost under field conditions. 36 This suggests the existence of a trade-off with those characteristics conferring an ecological advantage, and the possibility of using those traits to design herbicide-resistant weed management strategies.…”

Triple-resistant kochia [Kochia scoparia (L.) Schrad.] in Alberta

“…)is important to manage multiple-resistant kochia, which has become one of the most abundant and troublesome herbicide-resistant weeds in the southern prairies. The weakness in its life cycle is the short seed bank longevity (<1 yr), which can be exploited to reduce population abundance if weed management can mitigate seed return(Beckie et al 2018).…”