Genetic breeding of prosopis species from the "Great American Chaco"

Abstract

"Algarrobos" are a set of multipurpose tree species of the Prosopis genus, which consequently can have several breeding aims, including timber production, non-timber forest products and environmental services such as recovery of saline soils. The low-intensity breeding strategy for this group is presented here, detailing the identification of seed production areas in the natural forest for P. alba, P. chilensis, and P. flexuosa. Hybrid swarms are quite common, so the analysis of specific purity of natural stands is a basic step to manage the genetic resources of these species. Such analyses are conducted by means of morphological characters of leaves and isozyme patterns of seeds and can lead to the prescription of thinning in order to create seed production areas. Those basic materials are evaluated through provenance trials. The interest on using P. alba for afforestation has promoted the initiation of a high-intensity breeding program, including multi-site progeny testing with BLUP estimation, and backward, forward, family, and individual selection. The initial strategy of a unique base population dispersed in the entire Argentine Chaco was recently changed for the delineation of breeding zones. Vegetative propagation was adjusted as a useful tool for genetic improvement. Selection and breeding of beneficial soil microorganisms (rhizobia and mycorrhizae) accompany the breeding of the tree species: specific molecular markers were used for taxonomic identification and genetic characterization, and their symbiotic ability was evaluated.