PATHOGENICITY OF PRATYLENCHUS PENETRANS ON ONION

Pathogenicity of Pratylenchus penetrans on onion was tested both under greenhouse and microplot conditions. For the greenhouse study, seedlings of onion (Allium cepa) cultivar Tioga were inoculated with P. penetrans at 0, 3000, 6000, 9000, or 1200 females + juveniles/pot. In field microplots, onions were inoculated 0, 26500, 53000, 106000, or 212000 females + juveniles of P. penetrans/microplot. Cultural practices recommended by onion production in Idaho were carried out and data on fresh and dry weight of the plant top and roots, bulb diameter and weight, and nematode population in roots and soil were collected at harvest. Increasing inoculum levels led to significant reductions in onion growth and increased nematode population at harvest. Significant reduction in plant growth began at 3000 P. penetrans/pot or 26500/microplot. Bulb weight reduction ranged from 31.5% to 64.2% at the inoculum level of 26500 and 212000 P. penetrans/microplot, respectively, in field microplots. Maximum reduction in plant total dry weight was 84.2% at 12000 P. penetrans/pot under greenhouse conditions. This study will help onion growers in Idaho make decisions on whether or not to grow onions in a field with a specific population density of P. penetrans in the soil.