PARENT SESSION
Contributed Oral Session 63: Plant Genetics: Population Level Implications
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 519 A, Level 5, Palais des congrès de Montréal
The consequences of crop-wild relative hybridization in Lactuca: hybrid performance and long-term modeling.
Hooftman, Danny*,1, de Jong, Maaike1, Oostermeijer, Gerard1, van Tienderen, Peter1, den Nijs, Hans1, 1 Institute for Biodiversity and Ecosystem Dynamics, Amsterdam, The Netherlands
ABSTRACT- Hybridization between crops and wild relatives in the surrounding vegetation seems possible for many crop species. Subsequent introgression of crop-specific traits into wild relatives may occur and might lead to invasive introgressant populations. The probability for this process depends on (i) the level of gene flow and (ii) the fitness of the consecutive hybrid generations. However, few studies have used demographic monitoring of full life-cycles in comparing the performance of hybrids with their wild relatives. We created four hybrid generations between Lactuca sativa (Lettuce) and its entirely cross-fertile wild relative L. serriola; both are mainly autogamous annuals. Generations succeeding the F1 were derived via both the selfing- and the backcrossing pathway. Seeds of parental lines and all hybrid generations were individually sown in field plots and plants were monitored up to and including seed-set. All four-hybrid generations in the backcross pathway equaled L. serriola in individual phenotypes, including total seed production. Individual plants within the selfing pathway showed significantly lower seed production in advanced (3rd and 4th) generations. In contrast, survival rates of hybrids in both pathways were significantly higher in early hybrid generations due to additive heterosis, which resulted in a higher finite rate of population growth relative to L. serriola. This heterosis decreased in advanced hybrid generations. These data were entered in our matrix based stochastic model. In general, the likelihood of a rapid full displacement of L. serriola by single intermediate hybrid classes at realistic (low) outcrossing estimates is limited. More likely is the formation of a hybrid swarm in which backcrossing and autogamy intersperse. Such population thus contains a wide variety of genotypes and individual proportions of crop alleles next to pure wild type L. serriola. Facilitation of introgression of performance enhancing traits might be more likely in such dynamic hybrid swarms. This is due to continuous recombination and thus advanced transgression potential, compared to only segregating single hybrid classes.
Key words: hybridization, species displacement, plants with new traits, demographic modeling