Evaluation of Spinach Germplasm for Resistance to a New Race (Race 4) of Peronospora farinosa f. sp. spinaciae

Abstract

Spinach germplasm (707 accessions) from collections from six countries were screened for resistance to race 4 of the downy mildew pathogen Peronospora farinosa f. sp. spinaciae; these collections contained germplasm that originated from 41 countries. The predominant species examined was Spinacia oleracea L., however, eight accessions of S. turkestanica Iljin and two accessions of S. tetrandra Stev. were also tested. About 40 seedlings of each accession were inoculated. The cultivar St. Helens was included as a susceptible control in each test. The majority of accessions tested (>98%) were susceptible to race 4. Nine accessions exhibited some resistance to race 4 (9% to 38% of the seedlings within an accession were resistant), and two accessions, CGNO 9546 and SPI 82/87, exhibited a high level of resistance (60% and 80% resistant, respectively). Resistance identified in several of the accessions in this study may be useful for breeding for race 4 resistance.