Elizabeth L. Ogden

Inheritance of Cold Hardiness and Dehydrin Genes in Diploid Mapping Populations of Blueberry

Summary Studies of herbaceous plants suggest that cold hardiness is a complex, quantitatively inherited trait. Although development of cold hardiness is an integral part of the life cycle of woody perennial plants, studies on the genetic control of cold hardiness in woody perennials are scarce. A better understanding of the genetic control of cold hardiness would be valuable for developing more effective strategies to increase cold hardiness and, hence, climatic adaptation of woody perennial crops. In blueberry, three major dehydrins of 65, 60, and 14 kDa have been found to increase with cold acclimation and decrease with deac-climation. A comparison of these dehydrin levels among various blueberry cultivars and selections has revealed their level of accumulation to be closely associated with cold hardiness level. Efforts are underway to isolate and map the dehydrin genes of blueberry utilizing blueberry populations that segregate for cold hardiness in order to determine if the dehydrin genes map to or co-segregate with QTLs controlling cold hardiness. Progress has been made toward this goal. Cold hardiness levels were determined for a portion of the blueberry mapping populations (derived from testcrosses of Vaccinium darrowi Camp X V. caesariense Mackenz. F1s to another V. darrowi and another V. caesariense) using a laboratory controlled freeze-thaw regime, followed by visual assessment of injury to floral buds. As expected, the V. darrowi and V. caesariense parents were found to differ significantly in terms of cold hardiness levels (LT50s of -13°C and -20°C, respectively). Mean cold hardiness level of F1s (LT50 of -14.7°C) was skewed toward the V. darrowi parents suggesting that cold hardiness is a partially recessive trait. The sequence of a 2.0 kb cDNA clone, which encodes the 60 kDa blueberry dehydrin, was used to map a dehydrin-related gene to current linkage group 12 of the V. caesariense testcross population. A preliminary comparison of the segregation pattern of the dehydrin-related gene to that of the cold hardiness trait suggests that the marker does not segregate with cold hardiness.

High Levels of Heterozygosity Found for 15 SSR Loci in Solanum chacoense

Wild species-related germplasm is widely used to introduce new alleles and/or increase heterozygosity in cultivated species. Twenty-four SSR markers, specifically designed for cultivated potatoes, were evaluated to determine the extent of genetic variation within and among ten accessions of Solanum chacoense (chc). Fifteen of these markers were informative: there was no polymorphism in one of the markers, four of the markers showed evidence that more than one locus was being amplified, and the other four markers failed to consistently amplify products. Heterozygosity in these 10 accessions ranged from 33% to 87%. Variation among accessions was the largest proportion of variance for three markers, variation among genotypes within accessions was the largest proportion for three markers, and for the other nine markers variation within genotypes (chromosome to chromosome) was the largest proportion. Genetic similarity averaged 29.5% across markers. Where accessions have already been screened and found to possess the trait of interest, multiple genotypes from those accessions should be evaluated to identify genotypes with the greatest expression of the trait.ResumenEl germoplasma relacionado a especies silvestres se usa ampliamente para introducir nuevos alelos y/o aumentar la heterozigocidad en especies cultivadas. Se evaluaron 24 marcadores SSR específicamente diseñados para papas cultivadas, para determinar la amplitud de la variación genética dentro y entre diez introducciones de Solanum chacoense (chc). Quince de estos marcadores fueron informativos: no hubo polimorfismo en uno de los marcadores, cuatro de ellos mostraron evidencia de que más de un locus estaba siendo amplificado, y los otros cuatro marcadores fallaron para amplificar consistentemente los productos. La eterozigocidad en estas diez introducciones varió de 33% a 87%. La variación entre las accesiones fue la proporción mas grande de varianza para tres marcadores, la variación entre genotipos dentro de las introducciones fue la de mayor proporción para tres marcadores, y para los otros nueve la variación dentro de genotipos (cromosoma a cromosoma) fue la proporción más grande. La similitud genética promedió 29.5% entre los marcadores. En donde las accesiones ya han sido analizadas y que se encontró que poseen el carácter de interés, múltiples genotipos de estas introducciones deberían evaluarse para identificar genotipos con la mayor expansión del carácter.

LT25, LT50, and LT75 floral bud cold hardiness determinations for a diverse selection of Vaccinium genotypes

Ehlenfeldt, M. K., Rowland, L. J., Ogden, E. L. and Vinyard, B. T. 2015. LT25, LT50, and LT75 floral bud cold hardiness determinations for a diverse selection of Vaccinium genotypes. Can. J. Plant Sci. 95: 491-494. Freeze-bath cold hardiness results were used to calculate LT25 and LT75 values (temperatures causing 25% and 75% lethality, respectively) for a diverse selection of Vaccinium genotypes which had been previously analyzed for LT50 values. Overall, LT25 and LT75 values paralleled the LT50 values. Across genotypes, the LT25 was approximately 1.7°C (3.1°F) higher than the LT50, and the LT75 approximately 1.6°C (2.9°F) lower than the LT50 for any given date.