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United States Department of Agriculture

Agricultural Research Service

Research Project: Breeding Apple Rootstocks Tolerant to Abiotic Stresses and Resistant to Pests and Diseases

Location: Plant Genetic Resources

Title: Relationship of apple rootstock dwarfing loci (Dw1, Dw2) with scion leaf and fruit nutrient status

Authors
item Fazio, Gennaro
item Robinson, Terence -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 24, 2014
Publication Date: March 24, 2014
Citation: Fazio, G., Robinson, T. 2014. Relationship of apple rootstock dwarfing loci (Dw1, Dw2) with scion leaf and fruit nutrient status. [Abstract]. Horticultural Science, Fruit Crop Physiology Symposium. Oral Presentation.

Technical Abstract: Rootstock mediated apple tree dwarfing is influenced by the combination of two genetic factors Dw1 and Dw2 located respectively on Chromosome 5 and 11 of apple. The effect of these factors have been described with regards to tree architecture and productivity, however, little is known about their effect on mineral nutrient status of the scion. A replicated field experiment of Gala scion grafted onto a population of 186 rootstocks (progeny of Ottawa 3) segregating for dwarfing was used to monitor the dry matter concentration of nitrogen (N), potassium (K), phosphorous (P), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), copper (cu) manganese (Mn) and aluminum (Al) in leaf and fruit tissue. Molecular markers linked to the dwarfing loci were used to ascertain their effect on mineral nutrient concentrations by comparing means of contrasting alleles that were inherited by each rootstock in the population. Tree size was negatively correlated with fruit concentration of S, N, Cu, Mg in order of decreasing effect and significance. Tree size was positively correlated with leaf concentration of K, P and Ca in order of decreasing effect and significance. Markers associated with Dw1 showed that plants heterozygous for the dwarfing allele had significantly less leaf S than homozygous non-dwarfing plants, whereas Dw2 alleles had no significant effect. This is in contrast with fruit S which displayed significantly higher concentration in dwarfing plants where either Dw1 and Dw2 dwarfing alleles had displayed higher concentrations. Fruit N concentration was higher in fruit grown on rootstocks that possessed either of the dwarfing alleles following a similar pattern with S, the correlation between fruit S and N concentration was 0.79 (P<0.0001). More significant effects of Dw1 and Dw2 were observed on fruit concentration of Ca, P, K, Mg and Zn, and on leaf concentration of P, K, Ca, S and B. While Dw1 and Dw2 do not seem to be related directly in mode of action to mineral nutrition, segregation of these loci shows that they can have a significant effect on the nutrient status of leaves and fruit, each locus uniquely in size and direction of the effect. Further studies are needed to evaluate the implication of these data on tree physiology and fruit quality.

Last Modified: 10/25/2014
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