Breeding for resistance in Zantedeschia spp. (Araceae) against soft rot caused by Erwinia carotovora ssp carotovora

A huge problem in growing Zantedeschia (calla or arum lily) is the occurrence of soft rot caused by Erwinia carotovora ssp. carotovora. At Plant Research International, a research programme was started for finding and developing Erwinia-resistant genotypes of Zantedeschia. Hereto, a disease test was developed with which the level of resistance of clones, and therefore the variation in resistance within the genus, can be screened. The results show clearly, what is already known from practice, that Z. aethiopica is more resistant to the soft rot than species of section Aestivae. Interspecific hybrids between genotypes of the Aethiopica and the Aestivae section obtained using embryo rescue techniques deliver up till now only albino plants. An in vitro disease test was developed for screening these heterotrophic albino hybrids. There is variation for susceptibility/resistance within section Aestivae. Finding the genetics behind the resistance within this section is the next step in the programme.