Stability of Nonflowering Orchardgrass

Abstract

Orchardgrass (Dactylis glomerata L.) is a valuable pasture species in much of temperate humid North America. However, profuse and early flowering in spring creates management problems for graziers and reduces intake of livestock in a management‐intensive rotational grazing system. The objectives of this study were to estimate environmental stability, genotypic variability, and frequency of nonflowering and sparse‐flowering plants in two sparse‐flowering orchardgrass populations. Seven cultivars and 299 half‐sib families were evaluated for 2 yr at five locations between 42° and 47°N latitude. Sparse‐flowering populations WO‐SF‐B and WO‐SF‐C were later in maturity, produced fewer panicles per plant, and had higher frequencies of sparse‐flowering and nonflowering plants than the cultivars. Plants had varying levels of expression of the nonflowering trait, ranging from slightly sensitive (sparse flowering in one year) to highly sensitive (stable nonflowering across years), with highly sensitive plants found only within populations WO‐SF‐B and WO‐SF‐C. The nonflowering trait of orchardgrass appears to be controlled by floral‐regulation genes that are turned off by short‐day temperatures below a critical threshold. Such a threshold appears to exist for all orchardgrass plants, but is increased in those plants expressing the nonflowering trait.

Nitrogen Recycling and Flowering Time in Perennial Bioenergy Crops

“…Environmental factors to be considered include temperature and precipitation, which are variable from year to year, and photoperiod. Common garden experiments show that ecotypes of switchgrass are locally adapted, and the timing of reproductive development is correlated to the length of the local growing season (Cornelius and Johnston, 1941; Eberhart and Newell, 1959; McMillan, 1959, 1965; Hopkins et al, 1995; Sanderson and Wolf, 1995; Casler et al, 2004, 2007b; Berdahl et al, 2005; Casler, 2005). Variation also exists for leaf appearance rate, and end-of-season dormancy (Figure 1), all of which influences the length of active growth and biomass accumulation (McMillan, 1959; Van Esbroeck et al, 1997, 2004).…”

“…Development and flowering time in switchgrass has been recorded in a number of studies, which reveal latitudinal adaptation reflected by higher survival rates among local populations in reciprocal transplant experiments (Sanderson et al, 1999; Casler et al, 2004). Thus, flowering time or maturity is highly variable among switchgrass varieties, with photoperiodic differences along a north–south gradient (McMillan, 1959; Casler et al, 2004, 2007b; Casler, 2005).…”

“…Thus, flowering time or maturity is highly variable among switchgrass varieties, with photoperiodic differences along a north–south gradient (McMillan, 1959; Casler et al, 2004, 2007b; Casler, 2005). There also appears to be variability in the length of the flowering period with northern clones having 1 week between inflorescence exsertion and initial anthesis, while southern clones took 4–6 weeks (McMillan, 1959).…”

“…For example, CIR, an upland northern cultivar, showed the largest response to an artificially extended photoperiod (18 h) in a greenhouse with an increased yield of 129 and 98% in two trials, while Alamo showed no change (Van Esbroeck et al, 2003). In general in common garden experiments, lowland ecotypes have a heading date 2–4 weeks later than upland types (Casler et al, 2004; Cortese et al, 2010). In work from Taliaferro (2002), heading date was recorded for 113 switchgrass germplasms with variable flowering time [167–257 Days Of Year (DOY) (Taliaferro, 2002)].…”

“…The strong adaptation gradient results in some lowland varieties never flowering at northern locations and lacking cold tolerance, and upland varieties being heat intolerant and flowering too early for maximal biomass in southern locations (Sanderson et al, 1999; Casler et al, 2004, 2007a). In fact most switchgrass varieties are well adapted to their local environment and cannot be moved more than one hardiness zone without adverse affects on productivity and survival (Casler et al, 2004). The genetic parameters that control flowering are unknown and investigation into the endogenous and exogenous factors influencing flowering time will be valuable for developing region-specific cultivars.…”