Genetic variation in needle traits of whitebark pine (Pinus albicaulis) seedling families: Within-population variation at Crater Lake National Park

Abstract

Genetic variation in needle traits (number of rows of stomata, areal density of stomata, and density of stomata in a row, as well as needle length and needle width), seedling height growth, and early measures of blister rust (causal agent: Cronartium ribicola) resistance were examined among 22 openpollinated families of whitebark pine (Pinus albicaulis) from Crater Lake National Park (CLNP) in Oregon. Needle traits were examined for both the adaxial and abaxial sides. Needle traits were also assessed for 19 of 22 parent trees from CLNP. The adaxial side of the needle on average had more rows of stomata (3.3 versus 2.0 rows), a greater density of stomata within a row (12.3 versus 11.2 stomata per mm of row), and a much higher areal density of stomata (45.60 versus 22.00 stomata per mm2) than the abaxial side for the seedling families. Statistically significant variation among families was noted for many traits, particularly needle traits from the adaxial side of the needles as well as for height and rust infection (number of needle spots and number of stem symptoms, approximately 8 and 15 months post-inoculation). Individual tree heritabilities were low to moderate for needle traits (adaxial side), moderate for height, and very high for number of stem infections. Family mean correlations between stomate variables were generally statistically significant and moderate to high, with somewhat lower correlations between traits across the two surfaces. Needle length was uncorrelated with any of the other traits examined. The density of stomata (adaxial side) within a row showed a moderate correlation (0.47) to the number of needle spots; however, neither of these measures was correlated with the percentage of seedlings in a family with stem infections. The number of needle spots was only moderately correlated with the number of stem infections. Correlations between progeny and parental traits were generally significant and moderate to high. The parent–progeny mean correlations were highest for some of the traits on the abaxial side. There was evidence of significant differences in some traits between the 4 families from the east side (drier) and the 18 families from the west side of Crater Lake National Park, with families from the east side tending to have more stomata, shorter needles, shorter height, more stem infections, and a much higher percentage of infection 1 year after inoculation. The level of within-population variation was similar to that observed among populations from much of the range (seedlings grown in the same common garden study). This genetic variation may help buffer the Crater Lake population of whitebark pine against some biotic and abiotic factors in the future. Recently established genetic field trials at CLNP will provide a means of determining whether the characterized genetic variation contributes to maintenance of this population.

Parent Publication

• Proceedings of the IUFRO joint conference: Genetics of five-needle pines, rusts of forest trees, and Strobusphere; 2014 June 15–20; Fort Collins, CO

Citation

Sniezko, Richard A.; Hill, Jerry; Savin, Douglas P.; Mutch, Rob; Sticha, Julianne; Kegley, Angelia; Beck, Jen. 2018. Genetic variation in needle traits of whitebark pine (Pinus albicaulis) seedling families: Within-population variation at Crater Lake National Park. In: Schoettle, Anna W.; Sniezko, Richard A.; Kliejunas, John T., eds. Proceedings of the IUFRO joint conference: Genetics of five-needle pines, rusts of forest trees, and Strobusphere; 2014 June 15-20; Fort Collins, CO. Proc. RMRS-P-76. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 41-53.