Evaluation of pre-breeding resources for Pyrus spp.

Danielle Marie Guzman

doi:10.7273/000004015

In the U.S. there is an urgent need for dwarfing, precocious, cold tolerant, and disease resistant rootstocks for efficient production of pear (Pyrus communis L.). A key challenge is finding locally acclimated and genetically diverse parental material for breeding desirable rootstocks suitable for pear production in the U.S. To address this genetic resource gap, Pyrus communis L.cultivars, acclimated to the U.S environment, were utilized to develop two types of populations. A traditional population was developed in 2012 and consisted of 132 individuals derived from reciprocal crosses between 'Bartlett', 'D'Anjou', and 'Comice'. A putative mutant population was developed in 2013, utilizing gamma-irradiated pollen, comprising of 49 individuals recovered from crosses between 'Abbé Fetel', 'D'Anjou', 'Bartlett', and 'Comice'. In addition, a genetically diverse set of Pyrus germplasm was sourced from the USDA-ARS Corvallis Germplasm Repository as a pre-breeding resource for Pyrus rootstock development. Progeny from both types of populations were phenotyped for segregation of traits including, branch density, caliper, height, bark type, branch angle, and blind wood. Within the traditional population, ten of the individuals were potentially dwarfing and two individuals exhibited precocity as they flowered within four years after germination. Within the putative mutant population, four individuals were found to be potentially dwarfing. Target Region Amplification Polymorphism (TRAP) molecular markers were used to evaluate the extent of genetic interrelatedness, and diversity, within both types of populations and the germplasm collection. This analysis revealed that individuals in the traditional population formed two distinct groups. The individuals in the putative mutant population exhibited unpredictable grouping, perhaps as a consequence of gamma-irradiation of the pollen or to their true paternal lineage in case of any outcrossing, which is common during hybridization. The USDA germplasm collection separated into two groups, with no clear subgroups, most likely due to the inclusion of a genetically diverse set of individuals. Phenotypic and genetic diversity information generated for these pre-breeding resources is expected to enable appropriate selection of individuals for use as parental material for breeding experiments aimed at developing pear rootstocks for efficient pear production in the United States.

Evaluation of pre-breeding resources for Pyrus spp.

Files and links (1)

Abstract

Metrics

Details