Water scarcity is one of the major long-term problems that the turf industry faces worldwide, and the use of water on commercial and residential turf is increasingly regulated at national and regional levels. Both chronic shortages of water that occur in arid and semiarid zones (Eriyagama et al., 2009) and occasional extended droughts in humid regions (Carrow, 1996b) can increase the need to irrigate turf and pose challenges to maintain acceptable turfgrass quality. Drought avoidance refers to the plant’s ability to increase water uptake by developing a deep, extensive, and viable root system; and to reduce water loss through stomatal control (Huang, 2008; Huang et al., 1997a, 1997b).
Determining genetic potential in various root traits that are associated with drought mechanisms is an important screening process for developing turfgrasses with good drought response. Root length density (RLD, cm root cm−3 soil), has been widely used to quantify the extensiveness of the roots (Carrow, 1996a; Miller and McCarty, 1998), and is generally positively correlated with the rate of water uptake under well-watered conditions (Huang, 2000). Variations of RLD in a limited number of turfgrass species including cool-season and warm-season grasses have been documented. For example, Qian et al. (1997) reported that total root length in a 120-cm profile of ‘Mustang’ tall fescue (Festuca arundinaceae Schreb) was three times greater than ‘Meyer’ zoysiagrass (ZJ), ‘Midlawn’ hybrid bermudagrass [C. dactylon (L.) Pers. var. dactylon], and ‘Prairie’ buffalograss [Buchloe dactyloides (Nutt.) Engelm.] when grown in a greenhouse in calcined clay. This study was in accordance with Carrow (1996b), who documented similar results when comparing RLD between zoysiagrass and tall fescue.
However, high RLD alone does not translate to good performance during drought. In fact, high RLD in the surface soil would result in faster depletion of water and early onset of drought stress (Su et al., 2008). Profile characteristics of roots and associated drought avoidance mechanisms have been reported in several studies (Burton et al., 1954; Carrow, 1996b; Qian et al., 1997; Sheffer et al., 1987). Carrow (1996b), reported that high RLD close to the soil surface (3–10 cm) was related to greater leaf firing, while high RLD in the 20–60-cm horizon was associated with less leaf firing and wilting in tall fescue cultivars during drought.
The rate of root depth development (RRDD, cm/d) has been used as a potential criterion for selecting drought-resistant plants (Hamblin and Tennant, 1987). Root penetration of warm-season grasses (Burton et al., 1954) and rooting depth of 25 zoysiagrass cultivars (Marcum et al., 1995) were found to be correlated with drought response. Plants with rapid root extension were expected to develop deep roots, and the narrow-sense heritability of root extension in creeping bentgrass (Agrostis stolonifera L.) was high when grown in flexible root tubes (Lehman and Engelke, 1991). Acuña et al. (2010) developed a screening technique to evaluate bahiagrass (Paspalum notatum Flüggé) germplasm for RRDD, and a linear increase of root depth was reported. This technique can be potentially used to screen other turfgrass species for their root development.
Rooting patterns under well-watered conditions may not translate to rooting patterns under drought (Huang, 1999); however, the ability to develop deep and extensive root systems under well-watered conditions may ensure access to moisture deeper in the soil profile at the onset of drought. Correlations have been documented between rooting characteristics under well-watered conditions and survival under deficit irrigation in zoysiagrass (Marcum et al., 1995).
Common bermudagrass and zoysiagrass are widely used as warm-season turfgrass species in the southern United States for landscapes and sport fields (Trenholm et al., 2000; Unruh et al., 2013). African bermudagrass, indigenous to the Transvaal region of South Africa (De Wet and Harlan, 1971), has been used for turf (Juska and Hanson, 1964) and as a parent to produce interspecific bermudagrass hybrids (Burton, 1991; Kenworthy et al., 2006). There is no available information related to rooting traits in African bermudagrass.
The objectives of this study were to 1) determine RRDD and root profile characteristics of two bermudagrass species and two zoysiagrass species, 2) identify genotypes with great RRDD and high RLD in the lower profile. Both experimental lines and commercial cultivars were included in the study.
AcuñaC.A.SinclairT.R.MackowiakC.L.BlountA.R.QuesenberryK.H.HannaW.W.2010Potential root depth development and nitrogen uptake by tetraploid bahiagrass hybridsPlant Soil334491499
BurtonG.W.DeVaneE.H.CarterR.L.1954Root penetration, distribution and activity in southern grasses measured by yields, drought symptoms and P32 uptakeAgron. J.46229233
EissenstatD.M.1991On the relationship between specific root length and the rate of root proliferation: A field study using citrus rootstocksNew Phytol.1186368
EngelkeM.C.WhiteR.H.MortonS.J.MarcumK.B.1991Root development in selected varieties of each of four warm-season turfgrass genera. PR-Texas Agricultural Experiment Station
EriyagamaN.SmakhtinV.Y.GamageN.2009Mapping drought patterns and impacts: A global perspective. Research Report vii p. 23. International Water Management Institute
HamblinA.TennantD.1987Root length density and water uptake in cereals and grain legumes: How well are they correlated?Austral. J. Agr. Res.38513527
HuangB.1999Water relations and root activities of Buchloe dactyloides and Zoysia japonica in response to localized soil dryingPlant Soil208179186
HuangB.2000Role of root morphological and physiological characteristics in drought resistance of plants. In: R.F. Wilkinson (ed.). Plant-environment interactions. Marcel Inc. New York NY
HuangB.DuncanR.R.CarrowR.N.1997aDrought-resistance mechanisms of seven warm-season turfgrasses under surface soil drying.1. Shoot responseCrop Sci.3718581863
HuangB.DuncanR.R.CarrowR.N.1997bDrought-resistance mechanisms of seven warm-season turfgrasses under surface soil drying.2. Root aspectsCrop Sci.3718631869
HuangB.R.FryJ.D.1998Root anatomical, physiological, and morphological responses to drought stress for tall fescue cultivarsCrop Sci.3810171022
JuskaF.V.HansonA.A.1964Evaluation of Bermudagrass varieties for general-purpose turf. Agr. Hdbk. US Dep. Agr. 270 Washington DC
KenworthyK.E.TaliaferroC.M.CarverB.F.MartinD.L.AndersonJ.A.BellG.E.2006Genetic variation in Cynodon transvaalensis Burtt-DavyCrop Sci.4623762381
MarcumK.B.EngelkeM.C.MortonS.J.WhiteR.H.1995Rooting characteristics and associated drought resistance of zoysiagrassesAgron. J.87534538
MillerG.L.McCartyL.B.1998Turfgrass rooting characteristics of ‘Palmetto’ ‘FX-10’ and ‘Floratam’ St. Augustinegrasses and ‘Pensacola’ bahiagrass p. 177–187. Root demographics and their efficiencies in sustainable agriculture grasslands and forest ecosystems. Springer. Kluwer Academic Publishers Dordrecht Netherlands.
PompeianoA.GrossiN.VolterraniM.2012Vegetative establishment rate and stolon growth characteristics of 10 zoysiagrasses in southern EuropeHortTechnology22114120
SinclairT.R.SchrefflerA.WherleyB.DukesM.D.2011Irrigation frequency and amount effect on root extension during sod establishment of warm-season grassesHortScience4612021205
SteinkeK.ChalmersD.R.WhiteR.H.FontanierC.H.ThomasJ.C.WherleyB.G.2013Lateral spread of three warm-season turfgrass species as affected by prior summer water stress at two root zone depthsHortScience48790795
SuK.BremerD.J.KeeleyS.J.FryJ.D.2008Rooting characteristics and canopy responses to drought of turfgrasses including hybrid bluegrassesAgron. J.100949956
TrenholmL.E.CisarJ.L.UnruhJ.B.2000Bermudagrass for Florida lawns. Univ. of Florida. IFAS Extension. 26 Aug. 2015. <https://edis.ifas.ufl.edu/pdffiles/LH/LH00700.pdf>.
UnruhJ.B.TrenholmL.E.CisarJ.L.2013Zoysiagrass for Florida lawns. IFAS Extension. 26 Aug. 2015. <http://edis.ifas.ufl.edu/pdffiles/LH/LH01100.pdf>.
ZhouY.LambridesC.J.FukaiS.2014Drought resistance and soil water extraction of a perennial C4 grass: Contributions of root and rhizome traitsFunct. Plant Biol.41505519