Characterization of resistance to Alternaria spp. in wild relatives of carrot (Daucus carota L. ssp. carota)

A set of thirty wild relatives of carrot (CWR) (Daucus carota ssp. carota) was evaluated using bioassays for their resistance response to Alternaria dauci, A. radicina and A. alternata. The study included: i) pre-cultivation of carrot plants under optimized glasshouse conditions, ii) inoculation of detached leaf segments (A. dauci, A. alternata) and root slices (A. radicina) with defined fungi suspensions, iii) incubation within a climatic chamber and iv) quantification of the response to Alternaria infection using a digital image analysis system (DIAS). Statistically significant differences were observed between the CWRs with regard to their susceptibility to the different Alternaria species. Compared to the standards (Daucus carota ssp. sativus), twelve wild accessions were more resistant to A. dauci and nine to A. alternata. Significant differences between the CWRs in their response to A. radicina were also observed but the maximum level of resistance was similar to that found in the standards. In summary, eight CWRs appeared to possess a higher level of resistance to both A. dauci and A. alternata and, additionally, two of them almost achieved the level of resistance to A. radicina shown by the standards.