Location: Plant Genetic Resources
Title: Phenotypic diversity and QTL mapping of absorption and translocation of nutrients by apple rootstocks Authors
Submitted to: Aspects of Applied Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 24, 2013
Publication Date: N/A
Interpretive Summary: Root systems perform the essential function of absorbing nutrients from the soil. All commercial apple trees are grafted onto a variety of different rootstocks. Apple rootstocks are the foundation of a productive apple orchard by providing anchorage, access to water and nutrients, precocity, dwarfing and disease protection to grafted scion varieties like ‘Golden Delicious’ or ‘Honeycrisp’. In these experiments we found that different apple rootstocks have specific abilities to forage for essential mineral nutrients and transmit them to the scion variety. These specific abilities are associated with genetic factors which may be used to breed new apple rootstocks that increase the human nutrition potential of apples, and decrease fertilizer inputs and runoff in orchard operations.
Technical Abstract: Apple rootstocks perform the essential function of foraging for mineral nutrients contained in soil substrates. These nutrients are transported through rootstock vascular tissues to scion tissues and used in various essential plant functions including photosynthesis. In these experiments we measured the leaf mineral concentration for potassium (K), sodium (Na), phosphorous (P), calcium (Ca), copper (Cu), sulfur (S), zinc (Zn), magnesium (Mg), nickel (Ni) and molybdenum (Mo) in ‘Golden Delicious’ scion grafted on several commercial apple rootstocks and Gala scion grafted onto a segregating population of apple rootstocks. In the commercial rootstock experiment, significant rootstock genotype effects were detected for nutrients Ca, Cu, K, Mg, Mn, Na, P, S, Zn, and Mo. Rootstock G.935 stood out as conferring higher concentrations of Cu, K, P and Na. Several significant correlations were detected among nutrient concentrations, the highest being between Ca and Mg (0.778), P and Cu (0.787), P and S (0.703) and P and Ca (0.657). Several significant correlations were also detected among nutrient concentrations in the segregating population experiment, where between Mg and Ca (0.654) and between P and K (0.568). Quantitative trait locus analysis of the ‘Gala’ scion experiment reveled significant quantitative trait loci (QTLs) for leaf mineral concentrations for potassium (K), sodium (Na), phosphorous (P), calcium (Ca), copper (Cu), zinc (Zn), magnesium (Mg) and molybdenum (Mo). Segregation of marker alleles linked to the K1 QTL modulating potassium concentration in leaves had repercussions on several other nutrient concentrations in leaves. These experiments are setting the stage for breeding improved apple rootstocks on the basis of their genetic potential to absorb and translocate nutrients to grafted scions.