Breeding and Genetics of Caragana

Abstract

Research at the Indian Head Tree Nursery from 1947 to 1959 has produced an original breeding program to improve vigor of the Siberian pea-tree (Caragana arborescens, Lam.) for shelterbelt plantings in the Canadian Prairies. The species proved to be naturally cross-pollinated by insects and techniques for artificial self-and cross-pollinations were evolved. Seed viability problems related to maturity and dormancy were resolved to ensure maximum germination for progeny tests. Propagation of selections by softwood cuttings was superior to grafting for the production of clonal material. Two recessive factors, for the pendulant and albino characters, were identified and "tester" trees with these gene markers are utilized in controlled crosses to delete selections carrying these undesirable factors. Self-compatibility of 218 open-pollinated trees, which were selected on the basis of vigor ranged from zero (self-incompatible) to 99%. Cross-compatibility data, from reciprocal crosses of one self-compatible and three self-incompatible selections, segregated the four selections into three compatibility groups due to action of oppositional theory factors. A breeding program for the mass production of hybrid seed, by natural pollination of paired self-incompatible selections in isolated crossing blocks, has been developed. Steps to apply this program to improving the vigor, disease, insect and wood characteristics of caragana or of conifers, are detailed.