Yellow nutsedge is one of the most problematic weedy sedges in rice–soybean
systems of the Mississippi Delta region. An acetolactate synthase
(ALS)-inhibiting, herbicide-resistant (Res) yellow nutsedge
biotype was recently documented in eastern Arkansas, which showed
intermediary growth habit between yellow nutsedge and purple nutsedge and
also exhibited differential photoperiodic sensitivity to flowering. The
objectives of this study were to: (a) determine variation in reproductive
characteristics of the Res biotype and three susceptible
(Sus) yellow nutsedge biotypes, (b) understand the
influence of photoperiod on growth and reproduction, (c) understand the
potential role of seeds in population establishment, and (d) elucidate the
phylogenetic relationships between the Res yellow nutsedge
biotype and purple nutsedge. Tuber production per plant and tuber weight of
the Res biotype were less than that of the
Sus biotypes. Differences in quantitative traits, such
as shoot and tuber production existed between the Res and
Sus biotypes for photoperiods ranging from 12 to 16 h.
Generally, photoperiods greater than 12 h increased shoot development in all
yellow nutsedge biotypes, with differential responses among the biotypes.
Number of tubers reached the maximum for the Res biotype at
a 14-h photoperiod. Over a 90-d period, inflorescence formation was only
observed in the Res biotype with maximum flowering and seed
production in the 14-h photoperiod. Subsequent tests revealed up to 18% seed
germination, suggesting that seed could also play a role (in addition to
tubers) in the persistence and spread of the Res yellow
nutsedge. Phylogenetic analysis based on ribosomal DNA internal transcribed
spacer (ITS) regions and mitochondrial nad4 gene intergenic
spacer sequences indicated that the Res biotype was more
closely associated with Sus yellow nutsedge biotypes.
Nevertheless, 100% similarity for the nad4 gene sequences
between the Res yellow nutsedge biotype and a reference
purple nutsedge suggests that the Res biotype is likely a
result of hybridization between yellow and purple nutsedges, which perhaps
explains the intermediary growth characteristics observed in the
Res biotype.