Published online by Cambridge University Press: 20 January 2017
Yellow nutsedge is one of the most problematic weedy sedges in rice–soybeansystems of the Mississippi Delta region. An acetolactate synthase(ALS)-inhibiting, herbicide-resistant (Res) yellow nutsedgebiotype was recently documented in eastern Arkansas, which showedintermediary growth habit between yellow nutsedge and purple nutsedge andalso exhibited differential photoperiodic sensitivity to flowering. Theobjectives of this study were to: (a) determine variation in reproductivecharacteristics of the Res biotype and three susceptible (Sus) yellow nutsedge biotypes, (b) understand theinfluence of photoperiod on growth and reproduction, (c) understand thepotential role of seeds in population establishment, and (d) elucidate thephylogenetic relationships between the Res yellow nutsedgebiotype and purple nutsedge. Tuber production per plant and tuber weight ofthe Res biotype were less than that of the Sus biotypes. Differences in quantitative traits, suchas 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 allyellow nutsedge biotypes, with differential responses among the biotypes.Number of tubers reached the maximum for the Res biotype ata 14-h photoperiod. Over a 90-d period, inflorescence formation was onlyobserved in the Res biotype with maximum flowering and seedproduction in the 14-h photoperiod. Subsequent tests revealed up to 18% seedgermination, suggesting that seed could also play a role (in addition totubers) in the persistence and spread of the Res yellownutsedge. Phylogenetic analysis based on ribosomal DNA internal transcribedspacer (ITS) regions and mitochondrial nad4 gene intergenicspacer sequences indicated that the Res biotype was moreclosely associated with Sus yellow nutsedge biotypes.Nevertheless, 100% similarity for the nad4 gene sequencesbetween the Res yellow nutsedge biotype and a referencepurple nutsedge suggests that the Res biotype is likely aresult of hybridization between yellow and purple nutsedges, which perhapsexplains the intermediary growth characteristics observed in the Res biotype.