CROP QUALITY & UTILIZATION Seed Production of White Clover Cultivars and Naturalized Populations when Grown in a Pasture

tion, pest or disease resistance, or reseeding ability (Harris, 1987; Brink et al., 1999). Widdup et al. (1996) found Small-type white clover, Trifolium repens L., plants predominate that only 10 of 98 ecotype collections from throughout in most closely grazed pastures in the southeastern USA. The role of relative seed production in stand persistence of white clover types the eastern USA were ladino-type plants. Bouton et al. in pastures has not been quantified. This study compared the relative (1998) reported that ecotype collections in Georgia were seed production of seven small-type naturalized populations with that all intermediate types, even in pastures previously of seven large-type white clover cultivars and germplasms in a pasture. planted with large-type cultivars. All white clover plants All entries were space-planted into plots in a common bermudagrass collected from 27 closely grazed pastures in Alabama, [Cynodon dactylon (L.) Pers.] pasture at Mississippi State, MS, on Georgia, Louisiana, and Mississippi were small or intera Savannah fine sandy loam (fine-loamy, siliceous, semiactive, thermic mediate in plant type (Brink et al., 1999). Typic Fragiudult) in fall 1995 and 1996, and grazed with cattle prior to Persistence of white clover is not determined solely flowering and seed production. All naturalized populations averaged by survival of individual plants, but by persistence of about three times as many flowers and seed-bearing flowers as all the stand. White clover stands may persist under cool, cultivars other than ‘Louisiana S-1’ each year. Flower production differences were consistent throughout the study, though maximum moist conditions or climates by stolon survival. In cliflower production for naturalized populations was earlier in the season mates with periods unfavorable (i.e., hot, dry) for white than cultivars. Seed production differences were similar to flower clover growth, stands are maintained by hard seed proproduction, as cultivars averaged only 27 to 43% as much seed as duction and germination when conditions are favorable naturalized populations. The low growth stature and excessive seed for white clover growth (Harris, 1987). Both of these production of naturalized populations enable them to tolerate close survival strategies only succeed under appropriate mancontinuous grazing and have a greater opportunity to reseed in pasagement and environmental conditions. Promotion of tures than common large-type cultivars. This reseeding potential probone survival strategy is often at the expense of the other. ably contributes to the domination of small-type white clover in closely Each stolon node can form either a lateral stolon (prograzed pastures of the southeastern USA. moting vegetative persistence) or a flower (promoting seed production) but not both (Thomas, 1987; Pederson, 1995). Stolon density is closely related to vegetative M U.S. white clover breeding efforts during the persistence, while profuse flowering and seed produclast 50 yr have resulted in the release of largetion are inversely related to plant persistence (Gibson, type or ladino white clovers (Pederson, 1995). In the 1957; Piano and Annicchiarico, 1995). southeastern USA, these releases have included cultiSeed production differs among cultivars and among vars such as ‘Regal’, ‘Osceola’, ‘Tillman’, and ‘Will’ and types of white clover. Generally, small-type white clogermplasms SRVR and Brown Loam Syn. 2 (Caradus vers produce more flowers than large types, but large and Woodfield, 1997). Advantages of large-type over types have more seeds per flower than small types in intermediate or small-type white clover include greater temperate climates (Hollington et al., 1989; Marshall plant size, greater initial productivity, and improved et al., 1989; Williams et al., 1998). Differences among summer persistence due to larger, thicker stolons. Since cultivars have been noted not only for seed yield, but large-type cultivars have been the predominant type also for most seed yield components (Connolly, 1990; planted in southeastern USA grazing systems, it might Williams et al., 1998). Usually, studies of white clover be expected that most volunteer plants found in pastures seed production have taken place in areas of commercial would be large-type white clover. However, this is not seed production (Connolly, 1990; Oliva et al., 1994) the case. In most closely grazed pastures, small-type rather than in areas of pasture use. Seed production white clover predominates. This could be due to a numpotential of white clover for reseeding under pasture ber of factors, including grazing avoidance or tolerance, conditions has not been sufficiently evaluated. superior stolon branching and rooting, flower producIn a four-state trial, Brink et al. (1999) reported that under continuous stocking naturalized populations had G.A. Pederson and G.E. Brink, USDA-ARS, Crop Sci. Res. Lab., greater stolon length, stolon branching, and nodal rootWaste Mgmt. & Forage Res. Unit, 810 Hwy 12 E, Mississippi State, ing than cultivars. They also observed that flower and MS 39762-5367. Contribution of the USDA-ARS in cooperation with the Mississippi Agric. and Forestry Exp. Stn. Journal Article no. J9571 volunteer seedling production was greater for naturalof the Mississippi Agric. and For. Exp. Stn. Received 13 Sept. 1999. ized populations than cultivars. The objective of this *Corresponding author ([email protected]). study was to quantify and compare the relative seed yield and seed yield components of white clover cultiPublished in Crop Sci. 40:1109–1114 (2000).