Collecting horticulturally useful traits in the wild: Methodology to maximize genetic gain and minimize risk

Many ornamental crops have extremely narrow germplasm bases, e.g., Lilium longiflorum and Pelargonium ? domesticum. Thus, there is an imperative need for germplasm collection of wild species both of the crop and its relatives. The downy mildew (Plasmopara obducens) outbreak in Impatiens walleriana is a modern example of narrow germplasm risks with economic consequences. The perils of not collecting novel germplasm in species relatives include specific crop production requirements, which could have been eliminated if wild species had been collected at the commencement of ornamental breeding programs. The potential value to be found in collecting wild species of ornamental crop relatives is immensely proportional to the careful planning of collection trips, integration of local experts, serendipity in finding mutant genotypes, and risk management both during collection and thereafter in the breeding, domestication, and selection process. The objectives of this paper are to demonstrate the value of well-planned collecting trips to maximize genetic gain in future breeding and minimize risks in collected plant materials. More than 30 years of plant collecting experience throughout the world (S. Africa, Europe, N. America) and testing these findings with undergraduate students in a plant production course for new crop development are the basis for these recommendations and guidelines. Essential collection procedures include creating a crop ideotype to identify which traits are of importance in the new germplasm. These traits will direct the timing of when to collect, the best location of populations to maximize trait expression in wild populations, and the existence of natural hybrids, rather than collecting only when seeds are produced and implementing targeted (centers of origin, diversity) vs. random collections. Methods of population sampling to maximize genetic diversity, the numbers of genotypes to collect, and minimizing invasion risk also influence potential genetic gain.