International Turfgrass Society Research Journal最新文献

Frequent use of plant growth regulators (PGRs) may decrease the recovery of turfgrass from wear and competition with weeds. The response of new creeping bentgrass (Agrostis stolonifera L.) cultivars to PGRs is unknown. Therefore, we aimed to evaluate the response of several creeping bentgrass cultivars and common turfgrass weeds to PGRs. Creeping bentgrass cultivars (‘Penncross’, ‘L-93’, ‘007’, ‘V-8’, and ‘Tour Pro’) and weed species – goosegrass [Eleusine indica (L.) Gaertn.] and large crabgrass (Digitaria sanguinalis L.) – were examined. The PGR treatments were trinexapac-ethyl (TE) (48 and 96 g a.i. ha^–1) and prohexadione calcium (PC) (116 and 231 g a.i. ha^–1). Plants were cut to 2.5 cm after 2 wk, and aboveground plant tissue was weighed to obtain biomass. Only 116 g a.i. ha^–1 of PC was required to regulate creeping bentgrass, although the higher rate (96 g a.i. ha^–1) of TE was needed for moderate regulation [40–50% growth inhibition (GI)], regardless of the cultivar. Some creeping bentgrass cultivars exhibited a differential response to PGRs. The lowest response to TE (22–33% GI) was observed in ‘V-8’; however, ‘V-8’ was strongly regulated by PC (79–80% GI). Neither PGR successfully regulated goosegrass (14–30% GI), regardless of the rate, but moderate regulation of large crabgrass (40–49% GI) was achieved by TE at 96 g a.i. ha^–1, and PC at 116 and 231 g a.i. ha^–1. Recurrent PGR applications may shift turfgrass–weed competition dynamics towards weeds such as goosegrass; however, this effect may be PGR-specific.

Allelopathy is a commonly recognized but not fully understood method that could be utilized for weed management. Controlled environment studies in a growth chamber were conducted at Virginia Tech's Glade Road Research Facility in Blacksburg, VA, to determine whether aqueous leaf or root extracts from two Lolium arundinaceum (Schreb) Darbysh (tall fescue) cultivars grown under different growing temperature conditions affected the seed germination and growth of Poa annua L. (annual bluegrass). Two cultivars (‘Falcon III’ and ‘Kentucky 31’) of L. arundinaceum were maintained at cold (day/night 4.4:–1.1°C) or warm (day/night 32.2:26.7°C) conditions for 20 d. Leaf and root extracts were collected via destructive methods and applied to P. annua seed placed in petri dishes. The results indicated that aqueous leaf extracts of L. arundinaceum could inhibit P. annua seed germination, though there was no significant germination reduction with the root extract of L. arundinaceum. The results suggest that temperature may interact with other factors, such as L. arundinaceum cultivar, to influence its allelopathic potency on P. annua seed germination. These results further demonstrate that different cultivars of L. arundinaceum might have different allelopathic effects on P. annua germination.

Advanced sequencing techniques have improved the ability to identify and understand target-site resistance in herbicide-resistant species. Despite innovations in sequencing, polyploid species can still face issues that are typically not seen in diploid species, often because of the presence of conflicting subgenomes. Further confounding the difficulties of polyploidy is the α-tubulin gene, which has subgenomic duplication of gene family copies. Poa annua L., an allotetraploid, is a persistent weed in turfgrass that has developed resistance to multiple herbicide modes of action, including mitotic-inhibiting herbicides. Sequencing α-tubulin cannot be performed by simple Sanger sequencing to identify target-site mutations because of frequent nucleotide conflictions between the numerous α-tubulin copies present on both subgenomes, which was illustrated by vector cloning in combination with Sanger. Improved sequencing is needed to understand resistance to mitotic-inhibiting herbicides. Amplicon sequencing via Illumina technology was used to identify target-site mutations. Eighty-two populations resistant to mitotic-inhibiting herbicides were sequenced via next-generation sequencing. Seventy-five populations presented with the known single nucleotide polymorphism, Thr239Ile. The ability to successfully sequence and analyze α-tubulin data provides a vehicle for further insight into herbicide resistance.

Few projects have explored the long-term effects of N rates on multiple weed populations in the Pacific Northwest. The objectives of this research were to evaluate the effects of N application timing and annual N rates on weed population dynamics in a perennial ryegrass (Lolium perenne L.) stand in western Oregon. Factors in this project included N application timing [spring–heavy (April, May, June, and October), fall–heavy (May, September, October, and November), early spring and late fall (April, June, October, and November), and traditional spring and fall (May, June, September, and October)] and annual N rates (75, 150, and 300 kg N ha⁻¹ annually). An untreated control was also included in this project. The initial findings suggest that after 18 mo without herbicides, the highest annual N rate had the highest annual bluegrass populations but the lowest moss and broadleaf weed populations. The spring–heavy fertilization program at the low annual rate resulted in higher broadleaf weed populations than all other N application timing × N rate combinations. Data will continue to be collected from this experiment to determine the effects of N application timing and annual N rates on weed population dynamics.

Research was conducted from 2002 to 2006 to determine optimum application timings for the chemical seedhead suppression of annual bluegrass (AB) [Poa annua L. var. reptans (Hauskins) Timm.] by single applications of the plant growth regulators ethephon (EP) (2-chloroethylphosphonic acid) or EP plus trinexapac-ethyl (TE) [4-(cyclopropyl-alpha-hydroxymethylene)-3, 5-dioxo-cyclohexanecarboxylic acid ethyl ester]. The objectives were to evaluate AB seedhead suppression from single applications of EP and EP plus TE, and to evaluate the simple average-calculated growing degree-days (GDD) and Baskerville–Emin GDD models for their reliability to predict best application timing dates from year to year. Plots were established on a 10- to 15-yr-old AB fairway maintained at 1.5 cm and receiving 0.5 to 0.6 cm daily automatic irrigation throughout the growing season and 120 kg N ha^–1 yr^–1 from 2002 to 2006. The soil type is a Marlette sandy loam (fine-loamy, mixed, semiactive, mesic Oxyaquic Glossudalf). Plant growth regulators were applied at 3.74 and 0.08 kg a.i. ha^–1 for EP and TE, respectively, between 24 March and 13 May. Ethephon interacted with application timing in 2002 and 2003. Ethephon plus TE interacted with application timing in 2004, but not 2005 or 2006. Ethephon and EP plus TE did not provide less than 10% seedhead cover in 2003 or 2006, respectively. For EP and EP plus TE, application timing affected seedhead control in 3 of 5 yr.