Genetic variation in Zantedeschia spp. (Araceae) for resisance to soft rot caused by Erwina carotovora subsp. carotovora

Bacterial soft rot caused by Erwinia carotovora subsp. carotovora is a major disease in Zantedeschia spp., particularly in cultivars from the section Aestivae. The disease can partially be controlled by cultivation measures, so a combination with resistant cultivars could effectively protect the crop. However, resistant commercial Aestivae cultivars are not available yet. By means of a recently developed non-destructive resistance test, variation in aggressiveness was observed among five isolates of Erwinia carotovora subsp. carotovora without interactions between the isolates and three Zantedeschia accessions. Within eleven accessions of Z. aethiopica, variation was observed from almost complete to moderate resistance, while the Z. odorata accession was susceptible. All 21 Aestivae cultivars were susceptible. Within the Aestivae species, Z. elliotiana and Z. pentlandii were also susceptible, but within twelve accessions of Z. albomaculata, as well as in six accessions of Z. rehmannii, variation was found from susceptible to moderately resistant. Hence, new sources of resistance were identified that show good potentials for resistance breeding.