Managing Downy Mildew of Spinach: A Genomics-based Approach

Spinach is an economically important vegetable crop in the United States that has undergone dramatic industry changes in recent years and is valued at over $250 million annually. Spinach downy mildew disease, caused by the oomycete pathogen Peronospora farinosa f. sp. spinaciae (Pfs), continues to be a major production constraint for commercial spinach (Spinacia oleracea) worldwide. A total of 14 races of Pfs have been reported and a number of deviating isolates also have been described. Recently, an NIFA/SCRI grant was funded to develop: 1) a better understanding of the genetic and molecular basis of downy mildew resistance; 2) a more comprehensive understanding of the genetic diversity and global movement of races of the pathogen; 3) a real-time PCR based test to detect Pfs on seed; and 4) establish a comprehensive deployment of effective management strategies. Several isolates of Pfs have been partially sequences, as have several parents being used in the development of mapping populations. In addition, PCR based real-time primers have been developed which are both highly specific for Pfs as well as highly sensitive in detecting the pathogen on seed. Genotyping of a worldwide collection of Pfs is currently underway. In addition, efforts continue to develop markers linked to the six Pfs resistance loci, RPF1-RPF6.