Cold Acclimation Attributes of Two Asparagus Cultivars with Varying Patterns of Fern Senescence

Abstract

<jats:p>Adequate winterhardiness is crucial for yield stability of asparagus (<jats:italic>Asparagus officinalis</jats:italic>) cultivars in southern Ontario, Canada, and could be influenced by pattern of the fall fern senescence. Fern of cultivar Guelph Millennium (GM) turns yellow or senesces by mid-October, before that of cultivar Jersey Giant (JG), which often remains green until a killing frost. Early fern senescence could be a signal for cold acclimation competency and consequently winterhardiness, explaining the superior stand longevity and yield observed for GM compared with JG. A field experiment was conducted from mid-August to November to measure physiological parameters related to cold acclimation in fern, rhizome, and storage roots. During fall, fern chlorophyll concentration, rhizome nitrogen concentration, percent water of the crown, and storage root LT<jats:sub>50</jats:sub> (temperature at which 50% cell death occurs) decreased. Cultivars did not differ for storage root percent water; however, values were smaller (greater dehydration) for GM than JG in the rhizome. At the end of the sampling period, GM had higher and lower concentrations of rhizome low-molecular-weight, non-structural carbohydrates and sucrose, respectively, than JG, which could support a hypothesis of greater winterhardiness in GM. Storage root LT<jats:sub>50</jats:sub> values of –19 °C and the lack of cultivar differences for this trait, in conjunction with differences between GM and JG for rhizome traits thought to be important for freezing tolerance, suggest characteristics of the rhizome in conjunction with timing of fern senescence may be important in cold acclimation of asparagus.</jats:p>

Genetic Variation and Heritability Estimates for Indirect Measures of Freezing Tolerance during Fall Acclimation in Asparagus

“…1) and germplasm did not differ for all measures. These results are consistent with observations for GM and JG in a previous experiment (Landry and Wolyn, 2011) except for storage root percent water and both rhizome and storage root glucose, which did not differ between the two genotypes in the prior study but did differ among the germplasm studied here.…”

“…Concentrations of chlorophyll in the fern and proline and high-and low-molecular-weight fructans in storage roots and rhizomes were determined as previously described (Landry and Wolyn, 2011). Glucose and sucrose concentrations were estimated with a Megazyme raffinose/ sucrose/glucose kit (product K-RAFGL; Megazyme International Ireland, Bray, Ireland) (McCleary et al, 2006); methods of Landry and Wolyn (2011) were followed with one modification. The rhizome and storage root samples were incubated with 5 mL of 95% (v/v) ethanol to inactivate endogenous enzymes at the start of the assay.…”

“…Asparagus cultivars Guelph Millennium (GM) and Jersey Giant (JG) show different patterns of fall senescence and longevity in southern Ontario (Landry and Wolyn, 2011).…”

Freezing Tolerance Attributes during Spring Deacclimation for Three Asparagus Cultivars with Varying Adaptation to Southern Ontario

“…METABOLITE ANALYSIS. Carbohydrate concentrations were determined using commercial analysis kits (K-FRUC and K-RAFGL; Megazyme International Ireland, Bray, Ireland) according to Landry and Wolyn (2011) with one modification for simple carbohydrate estimates: at the start of the analysis, the rhizome and storage root samples were incubated with 5 mL of 95% (v/v) ethanol at room temperature to inactivate endogenous enzymes. Proline was quantified with ninhydrin (Landry and Wolyn, 2011).…”

“…Analysis of fall acclimation suggested GM asparagus had greater freezing tolerance than JG due to its early senescence and decreased percentage water, increased low-molecularweight nonstructural carbohydrate concentration, and decreased sucrose concentration in the rhizome (Landry and Wolyn, 2011). For a seedling experiment in controlled environments, where cold acclimation induced early senescence of GM as observed in the field, this cultivar had lower LT 50 values (increased freezing tolerance) compared with JG after subfreezing acclimation, which was associated with high proline levels in crowns (Landry and Wolyn, 2012).…”