Apium Wild Species: Novel Sources for Resistance to Late Blight in Celery

Screening of 144 varieties of celery A. graveolens L. for late blight (Septoria apiicola Speg.) resistance resulted in the detection of significant differences for disease reaction. However, each accession displayed greater than 25 % leaf necrosis area due to the disease pathogen. Hence the magnitude of infection in the least susceptible plants was still too great to use them as a valuable source for resistance. The wild species A. chilense and A. panul exhibited a few discrete yellow spots with very little, if any, pycnidial development. This type of resistance was not observed in any accession of celery screened. The degree of resistance was intermediate in the F₁ hybrids between A. graveolens × A. chilense and A. graveolens×A. panul, indicating incomplete dominance. The resistance to late blight found in these wild species and their ability to cross with celery provides a novel germplasm source for breeding celery lines with improved resistance to late blight.