Can Pl Resistance Gene in Sunflower Line D4 be Used to Differentiate the Pathogenicity in Four Plasmopara halstedii (Sunflower Downy Mildew) Races 304, 314, 704 and 714?

Abstract

In order to clarify the role of PlPMI3 resistance gene in sunflower differential lines D4 for differentiation the pathogenicity in Plasmopara halstedii (sunflower downy mildew), analyses were carried out in two groups including four pathotypes which overcome and do not overcome PlPMI3 (Pl gene has still not been mapped) resistance gene. Based on the reaction for the P. halstedii isolates to sunflower hybrids varying only in Pl resistance genes, there were no virulence differences for the two groups. Index of aggressiveness was calculated for pathogen isolates and revealed the presence of significant differences between isolates of races 304 and 314; however, there were no aggressiveness differences for 7xx races. Regarding the life-history trait and the genetic architecture of the pathogen: there were morphological and genetic variations for the four P. halstedii isolates without a correlation with pathogenic diversity. The importance of the PlPMI3 resistance gene to differentiate the pathogenicity in sunflower downy mildew was discussed.