Relative fitness and competitive ability of the crop-wild hybrid (Raphanus raphanistrum x R. sativus) versus the wild radish (R. raphanistrum).

Abstract

Crop-wild hybrid (Raphanus sativus x R. raphanistrum) and wild radishes (R. raphanistrum) were grown under three sets of experimental conditions: limited nutrient availability, shared resources, and with interspecific competition with Lolium perenne, a perennial ryegrass. Under the former two conditions, the hybrid radishes flowered significantly later and were significantly larger at bolting than the wild radishes. Ovule number was not significantly different between the two radish genotypes in either treatment. In contrast, in the presence of the ryegrass, the wilds were significantly larger at day 24 than the hybrids. It was also found that the crop-wild hybrids have significantly reduced male fitness in terms of pollen viability. These results demonstrate that under natural competitive conditions, the wilds, at least in terms of vegetation, have an advantage over the hybrids, which may decrease hybrid fitness and thus the persistence of crop genes in wild populations of radish.