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Cold hardiness increases with age in juvenile Rhododendron populations.

Lim CC, Krebs SL, Arora R - Front Plant Sci (2014)

Bottom Line: In contrast, CH of the mature parent plants (>10 years old) did not change significantly over the same evaluation period.In leaf samples from a natural population of R. maximum, CH evaluations over 2 years resulted in an average T max value for juvenile 2- to 3-year-old plants that was 9.2°C lower than the average for mature (~30 years old) plants.The feasibility of identifying hardy phenotypes at juvenile period and research implications of age-dependent changes in CH are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Horticulture, Iowa State University , Ames, IA, USA.

ABSTRACT
Winter survival in woody plants is controlled by environmental and genetic factors that affect the plant's ability to cold acclimate. Because woody perennials are long-lived and often have a prolonged juvenile (pre-flowering) phase, it is conceivable that both chronological and physiological age factors influence adaptive traits such as stress tolerance. This study investigated annual cold hardiness (CH) changes in several hybrid Rhododendron populations based on T max, an estimate of the maximum rate of freezing injury (ion leakage) in cold-acclimated leaves from juvenile progeny. Data from F2 and backcross populations derived from R. catawbiense and R. fortunei parents indicated significant annual increases in T max ranging from 3.7 to 6.4°C as the seedlings aged from 3 to 5 years old. A similar yearly increase (6.7°C) was observed in comparisons of 1- and 2-year-old F1 progenies from a R. catawbiense × R. dichroanthum cross. In contrast, CH of the mature parent plants (>10 years old) did not change significantly over the same evaluation period. In leaf samples from a natural population of R. maximum, CH evaluations over 2 years resulted in an average T max value for juvenile 2- to 3-year-old plants that was 9.2°C lower than the average for mature (~30 years old) plants. A reduction in CH was also observed in three hybrid rhododendron cultivars clonally propagated by rooted cuttings (ramets)-T max of 4-year-old ramets was significantly lower than the T max estimates for the 30- to 40-year-old source plants (ortets). In both the wild R. maximum population and the hybrid cultivar group, higher accumulation of a cold-acclimation responsive 25 kDa leaf dehydrin was associated with older plants and higher CH. The feasibility of identifying hardy phenotypes at juvenile period and research implications of age-dependent changes in CH are discussed.

No MeSH data available.


Related in: MedlinePlus

Cold hardiness (Tmax) distribution of a BC population over three consecutive years (A-C).
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Figure 2: Cold hardiness (Tmax) distribution of a BC population over three consecutive years (A-C).

Mentions: Tmax from 10 progeny in two reciprocal BC populations— R. fortunei × R. “Ceylon” and R. “Ceylon” × R. fortunei— were annually determined between 1 and 3 years of age. Because the difference between the variances in mean Tmax was nonsignificant in the reciprocal crosses (F-test not shown), the Tmax data were pooled as a single BC population (n = 20). Similar progeny scores from the reciprocal crosses suggest that there is no maternal inheritance determining CH. Average Tmax values in the BC population were 8.5 and 11.2°C less hardy than F2 populations of the same age—3 and 4 years old, respectively. Although both groups are derived from R. catawbiense and R. fortunei, the BC population has 25% more contribution from R. fortunei, the less cold-hardy parent, than the F2. Like the F2 population, progeny at 3, 4, and 5 years of age varied continuously for Tmax (Figure 2), becoming progressively more cold-hardy. The increases in CH were significant—3.7°C (from 3- to 4-year-old) and 5.6°C (from 4- to 5-year-old). By the fifth year, some of the BC seedlings had set flower buds, an indication of physiological maturity (phase change). However, average CH in the 5-year-old progeny (–28.2°C) was still lower than mature CH of the more cold-sensitive parent, R. “Ceylon” (–32.0°C).


Cold hardiness increases with age in juvenile Rhododendron populations.

Lim CC, Krebs SL, Arora R - Front Plant Sci (2014)

Cold hardiness (Tmax) distribution of a BC population over three consecutive years (A-C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4199316&req=5

Figure 2: Cold hardiness (Tmax) distribution of a BC population over three consecutive years (A-C).
Mentions: Tmax from 10 progeny in two reciprocal BC populations— R. fortunei × R. “Ceylon” and R. “Ceylon” × R. fortunei— were annually determined between 1 and 3 years of age. Because the difference between the variances in mean Tmax was nonsignificant in the reciprocal crosses (F-test not shown), the Tmax data were pooled as a single BC population (n = 20). Similar progeny scores from the reciprocal crosses suggest that there is no maternal inheritance determining CH. Average Tmax values in the BC population were 8.5 and 11.2°C less hardy than F2 populations of the same age—3 and 4 years old, respectively. Although both groups are derived from R. catawbiense and R. fortunei, the BC population has 25% more contribution from R. fortunei, the less cold-hardy parent, than the F2. Like the F2 population, progeny at 3, 4, and 5 years of age varied continuously for Tmax (Figure 2), becoming progressively more cold-hardy. The increases in CH were significant—3.7°C (from 3- to 4-year-old) and 5.6°C (from 4- to 5-year-old). By the fifth year, some of the BC seedlings had set flower buds, an indication of physiological maturity (phase change). However, average CH in the 5-year-old progeny (–28.2°C) was still lower than mature CH of the more cold-sensitive parent, R. “Ceylon” (–32.0°C).

Bottom Line: In contrast, CH of the mature parent plants (>10 years old) did not change significantly over the same evaluation period.In leaf samples from a natural population of R. maximum, CH evaluations over 2 years resulted in an average T max value for juvenile 2- to 3-year-old plants that was 9.2°C lower than the average for mature (~30 years old) plants.The feasibility of identifying hardy phenotypes at juvenile period and research implications of age-dependent changes in CH are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Horticulture, Iowa State University , Ames, IA, USA.

ABSTRACT
Winter survival in woody plants is controlled by environmental and genetic factors that affect the plant's ability to cold acclimate. Because woody perennials are long-lived and often have a prolonged juvenile (pre-flowering) phase, it is conceivable that both chronological and physiological age factors influence adaptive traits such as stress tolerance. This study investigated annual cold hardiness (CH) changes in several hybrid Rhododendron populations based on T max, an estimate of the maximum rate of freezing injury (ion leakage) in cold-acclimated leaves from juvenile progeny. Data from F2 and backcross populations derived from R. catawbiense and R. fortunei parents indicated significant annual increases in T max ranging from 3.7 to 6.4°C as the seedlings aged from 3 to 5 years old. A similar yearly increase (6.7°C) was observed in comparisons of 1- and 2-year-old F1 progenies from a R. catawbiense × R. dichroanthum cross. In contrast, CH of the mature parent plants (>10 years old) did not change significantly over the same evaluation period. In leaf samples from a natural population of R. maximum, CH evaluations over 2 years resulted in an average T max value for juvenile 2- to 3-year-old plants that was 9.2°C lower than the average for mature (~30 years old) plants. A reduction in CH was also observed in three hybrid rhododendron cultivars clonally propagated by rooted cuttings (ramets)-T max of 4-year-old ramets was significantly lower than the T max estimates for the 30- to 40-year-old source plants (ortets). In both the wild R. maximum population and the hybrid cultivar group, higher accumulation of a cold-acclimation responsive 25 kDa leaf dehydrin was associated with older plants and higher CH. The feasibility of identifying hardy phenotypes at juvenile period and research implications of age-dependent changes in CH are discussed.

No MeSH data available.


Related in: MedlinePlus