Bermudagrass ( Cynodon dactylon Pers.) is an important warm-season perennial used extensively for turf, forage, soil conservation and remediation worldwide. However, limited genomic information has hindered the application of molecular tools towards understanding genome evolution and in breeding new cultivars. We genotype a first-generation selfed population derived from the tetraploid (4x = 36) ‘A12359’ using genotyping-by-sequencing. A high-density genetic map of 18 linkage groups (LGs) is constructed with 3,544 markers. Comparative genomic analyses reveal that each of nine homeologous LG pairs of C. dactylon corresponds to one of the first nine chromosomes of Oropetium thomaeum . Two nested paleo-ancestor chromosome fusions (ρ6-ρ9-ρ6, ρ2-ρ10-ρ2) may have resulted in a 12-to-10 chromosome reduction. A segmental dissemination of the paleo-chromosome ρ12 (ρ1-ρ12-ρ1, ρ6-ρ12-ρ6) leads to the 10-to-9 chromosome reduction in C. dactylon genome. The genetic map will assist in an ongoing whole genome sequence assembly and facilitate marker-assisted selection (MAS) in developing new cultivars.

No abstract

Golf course water use continues to be highly scrutinized. Information is limited regarding minimal levels of reference evapotranspiration (ETo)‐based irrigation needed to maintain adequate summer fairway performance and autumn recovery. The objectives of this 2‐yr study were to (i) characterize ‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] fairway response to irrigation levels of 0.6, 0.45, 0.3, and 0.0 × ETo, with and without simulated summer traffic and (ii) evaluate effects of irrigation and traffic on autumn recovery at full irrigation levels. Without traffic, ≥0.3 × ETo was generally adequate for maintaining acceptable quality both years. Withholding irrigation altogether resulted in unacceptable turf quality both years. Summer traffic reduced quality and percentage green cover at all irrigation levels. Canopy temperatures increased with diminishing irrigation, with up to 25°C difference between 0.6 × ETo and unirrigated plots. Upon resumption of full irrigation in autumn, deficit and unirrigated treatments rebounded to 80 to 90% green cover by late autumn. However, in Year 2, only irrigated plots recovered to adequate cover levels, with unirrigated plots suffering substantial injury with only 30% green cover by late autumn. While no rooting differences were detected in Year 1, turf the 0.3 × ETo and unirrigated treatments had lower root dry weights than 0.45 and 0.6 × ETo treatments in Year 2. These data suggest provision of minimal deficit irrigation levels during summer drought may be important for sustaining turf viability and promoting autumn recovery of bermudagrass following successive years of summer drought stress.

Cynodon transvaalensis Burtt‐Davy is frequently used to cross with C. dactylon Pers. in the creation of F1 hybrid cultivars that are some of the most widely used in the worldwide turf industry. However, molecular resource development in this species is limited. Accordingly, the objectives of this study were to construct a high‐density genetic map, and to identify genomic regions associated with establishment rate. In this study, we constructed the first high‐density linkage map for African bermudagrass using a genotyping by sequencing approach based on 109 S1 progenies. A total of 1,246 single nucleotide polymorphisms and 32 simple sequence repeat markers were integrated in the linkage map. The total length of nine linkage groups was 882.3 cM, with an average distance of 0.69 cM per interval. Four genomic regions were identified to be associated with sod establishment rate. The results provide important genetic resources towards understanding the genome as well as marker‐assisted selection for improving the establishment rate in bermudagrass breeding.

Core aerification iscommonly used to manage organic matter and improve soil physical conditions of putting greens. Most methods of core aerification are labor intensive and temporarily reduce the playability of greens. Less invasive cultivation techniques are available, but their specific effects on playability and drainage properties of greens are often less understood. The objective of this study was to assess the shortterm effects of air-injection cultivation (AIC), sand-injection cultivation (SIC), and hollow-tine cultivation (HTC) on playability characteristics and soil physical properties of putting greens. A field study was conducted at the Oklahoma State University Turfgrass Research Center in Stillwater, OK, on a creeping bentgrass (Agrostis stolonifera L. 'Penncross') green from September 2017 to September 2019. Cultivation type and timing of application were arranged in a split-plot design with four replications. Cultivation type was defined as either AIC, SIC, or HTC, and each was applied in spring, summer, and fall. Compared with the control, HTC reduced surface firmness by 5% at 28 d after cultivation event (DACE), increased infiltration by 87% at 28 DACE, reduced ball roll distance by 6% up to 14 DACE, and reduced normalized difference vegetation index (NDVI) by 10% up to 14 DACE. Neither AIC nor SIC had a detectable effect on measured variables. Results suggest a single application of AIC or SIC has minimal short-term effects on soil physical properties or surface playability of putting greens.