|FORSLINE, PHILIP - Former ARS Employee|
Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2014
Publication Date: 12/11/2014
Citation: Fazio, G., Chao, C.T., Forsline, P., Richards, C.M., Volk, G.M. 2014. Tree and root architecture of Malus sieversii seedlings for rootstock breeding. Acta Horticulturae. 1058:585-594.
Interpretive Summary: The research described in this manuscript involves the description of tree architectures of wild apple trees and how they might be utilized to develop improved apple rootstocks. For instance, the presence of spines is undesirable during the propagation phases of apple trees and crossing current spiny rootstocks with wild spine-free parents might result in improved spine-free material. Another example of a desirable trait is the induction of flat branching, which is associated with higher productivity of an apple tree. Trees with flat branched, open canopies were found in this germplasm. The information is being used to select new parents for apple rootstock breeding.
Technical Abstract: The foundation of a successful apple orchard is in large part the rootstock used to establish the trees in that orchard. Apple rootstocks can impart several important architectural tree characters to the scion, among which are reduction in tree size and early production of flowers/fruit. It is probable that similar root-mediated characteristics exist in natural ancestral apple populations such as Malus sieversii, a species known to have traits associated with tolerance to several biotic and abiotic stresses. We sought to understand the genetic determinism of tree architecture of M. sieversii seedlings by measuring several scion and root architecture characters on a total of 1180 high resolution images of dormant 1 year old trees. These images were analyzed to ascertain number of growing points (tips), tree volume and total length of branch canopy, flat branching, presence of spines, root mass, number of primary roots, and number of thick roots. Analysis of means revealed significant inherited differences for several traits related to tree and root architecture, especially for flat branching, presence of spines, number of primary roots and root mass. Such differences were also detected between sites of origin of the mother trees. This information is being used to select parents for a new generation of rootstocks that will be evaluated in years to come.