Phenotypic groups ofPlasmopara halstedii(downy mildew) based on interactions with sunflower plants

Evolution of Two Components of Pathogenicity in Plasmopara halstedii (Downy Mildew) under Sunflower Qualitative Resistance Selection Pressure

“…These isolates belong to several races and may be found to be an effect of additional avirulence genes in P. halstedii isolates as observed for another oomycete P. infestans (Montarry et al, 2010). Second, isolates belong to 7xx races that accumulate a large number of avirulence genes and show the lowest levels of aggressiveness, compared with isolates belong to 100 and 3xx races that accumulate a small number of avirulence genes and show the highest levels of aggressiveness (Sakr, 2012(Sakr, , 2013(Sakr, , 2014a(Sakr, , 2014b(Sakr, , 2014d(Sakr, , 2014e, 2015b. For progeny isolates, appearance of the highest virulent isolates of 7xx races compared with the least virulent isolates of 3xx races in response to Pl genes resistance selection pressure is costly due to trade-offs with aggressiveness.…”

“…Fourteen different races of this pathogen have now been characterized, nine of which emerged in the last ten years (Delmotte et al, 2008;Sakr, 2014b). High percentage infection, short-latent period, high sporulation density, and significant reduction in the length of the hypocotyl represent high aggressiveness (Sakr, 2012(Sakr, , 2013(Sakr, , 2014a(Sakr, , 2014b(Sakr, , 2014c(Sakr, , 2014d(Sakr, , 2014e, 2015a. Single zoosporangium isolates of parental isolate 100 and progeny isolates of races 300, 304 and 314 were more aggressiveness that single zoosporangium isolates of parental isolate 710 and progeny isolates of races 704 and 714 (Fig.…”

“…To characterize aggressiveness criteria: percentage infection, latent period, sporulation density and reduction of hypocotyl length for 35 P. halstedii single zoosporangium isolates (Sakr, 2012(Sakr, , 2013(Sakr, , 2014a(Sakr, , 2014b(Sakr, , 2014c(Sakr, , 2014d(Sakr, , 2014e, 2015a, one INRA inbred line ʻFUʼ was used. It carried no Pl gene, but is known to a have high level of quantitative resistance (Tourvieille de Labrouhe et al, 2008).…”

“…Characterization of the highest and the least virulent P. halstedii races of could be assessed in response to Pl2 resistance gene in sunflower differential line D3 (Sakr, 2012(Sakr, , 2013(Sakr, , 2014a(Sakr, , 2014b. Based on the virulence reaction for the seven P. halstedii pathotypes to D3, we can divide them into two groups.…”

“…halstedii is characterized by a high level of evolutionary potential expressed by high virulence, aggressiveness and a great potential in developing new races (Delmotte et al, 2008;Tourvieille de Labrouhe et al, 2010;Ahmed et al, 2012;Sakr, 2012Sakr, , 2013Sakr, , 2014aSakr, , 2014bSakr, , 2014cSakr, , 2014dSakr, , 2014e, 2015aSakr, , 2015b. Even thought some studies aimed to analyze the influence of qualitative sunflower selection pressure on virulence in both experimental and filed conditions (Delmotte et al, 2008;Tourvieille de Labrouhe et al, 2010;Ahmed et al, 2012;Sakr, 2014aSakr, , 2014bSakr, , 2014e, 2015b, a number of questions regarding its influence on evolution of aggressiveness (Sakr, 2014b, morphological (Sakr, 2014c), and genetic characteristics (Sakr, 2012(Sakr, , 2013(Sakr, , 2014d(Sakr, , 2014e, 2015a(Sakr, , 2015b have still remained unanswered. In this study, phenotypic analyses (morphological and pathogenic) and genetic characteristics were analysed for seven P. halstedii pathotypes: race 100 present in France since the 1966, race 710 introduced from the USA during the 1980s (Tourvieille de Labrouhe et al, 2000, 2010), and five progeny pathotypes of races 300, 304, 700, 704 and 714 originated from an initial mixture of pathotypes 100 and 710 (Tourvieille de Labrouhe et al, 2010;Sakr, 2014aSakr, , 2014bSakr, , 2014e, 2015b.…”