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1

Can we enhance durable resistance against Plasmopara halstedii [sunflower downy mildew]?

100%
Sakr N.
Journal of Plant Protection Research
|
2010
|
tom 50
|
nr 1
15-21
Sunflower downy mildew caused by Plasmopara halstedii is one of the most potentially important diseases. So far, a complete, major gene resistance (Pl) has been used successfully, but with the appearance of eight races in France since 2000, research on more durable resistance was undertaken. In this study, we present new results concerning the evolution of pathogenicity of P. halstedii under conditions of re-enforced infection and different Pl gene selection pressures. Moreover, we imagine the evolution of virulence and aggressiveness of P. halstedii under a mixture model of sunflower inbred lines carrying the two types of resistance which may enhance durable resistance against it. Examples of host-parasite interactions including the influence of plant mixture models against pathogens are equally presented to understand how the pathogen develops its pathogenicicity.
2

Components of quantitative resistance to downy mildew [Plasmopara halstedii] in sunflower [Helianthus annuus]

100%
Sakr N.
Journal of Plant Protection Research
|
2009
|
tom 49
|
nr 3
297-301
Components of quantitative resistance in sunflower (Helianthus annuus) to Plasmopara halstedii, the pathogen causing downy mildew, were investigated. Percentage infection, latent period, sporulation density and reduction of hypocotyl length were compared on two sunflower lines showing different levels of quantitative resistance in the field infected with different P. halstedii strains of races 100, 300, 710 and 714 in controlled conditions. The inbred line BT, rather susceptible in the field, showed a higher percentage infection, a higher sporulation density, a shorter latent period and less reduced hypocotyl length than inbred line FU, which showed a greater resistance in the field. The very good resistance of inbred line FU observed in the field was confirmed by the measurements of quantitative resistance criteria described in this study. Percentage infection of FU was 1.4% less than BT, latent period of BT was 12.4% less than FU, sporulation density of FU was 22.3% less than BT and reduced hypocotyl length of BT was 15.3% less than FU. It seems that the criteria such as latent period, sporulation density and reduction of hypocotyl length may be used to measure quantitative resistance in sunflower to P. halstedii.
3
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Silicon control of bacterial and viral diseases in plants

100%
Sakr N.
Journal of Plant Protection Research
|
2016
|
tom 56
|
nr 4
Silicon plays an important role in providing tolerance to various abiotic stresses and augmenting plant resistance against diseases. However, there is a paucity of reports about the effect of silicon on bacterial and viral pathogens of plants. In general, the effect of silicon on plant resistance against bacterial diseases is considered to be due to either physical defense or increased biochemical defense. In this study, the interaction between silicon foliar or soil-treatments and reduced bacterial and viral severity was reviewed. The current review explains the agricultural importance of silicon in plants, refers to the control of bacterial pathogens in different crop plants by silicon application, and underlines the different mechanisms of silicon-enhanced resistance. A section about the effect of silicon in decreasing viral disease intensity was highlighted. By combining the data presented in this study, a better comprehension of the complex interaction between silicon foliar- or soil-applications and bacterial and viral plant diseases could be achieved.
4

A plant mixture model against Plasmopara halstedii [sunflower downy mildew]

100%
Sakr N.
Journal of Plant Protection Research
|
2010
|
tom 50
|
nr 2
125-129
Sunflower downy mildew caused by Plasmopara halstedii is one of the most potentially important diseases. So far, a complete, major gene resistance (Pl) has been used successfully. But, with the appearance of eight races in France since 2000, research on more durable resistance was undertaken. In this study, we presented new results concerning the evolution of pathogenicity in P. halstedii under conditions of re-enforced infection and different Pl gene selection pressure. Moreover, we studied the evolution of virulence and aggressiveness of P. halstedii under a mixture model of sunflower inbred lines carrying the two types of resistance (qualitative and quantitative). This sunflower model may enhance durable resistance against P. halstedii.
5
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Pathogenicity and quantitative resistance in Mediterranean durum and bread wheat cultivars of Syrian origin towards Fusarium head blight agents under controlled conditions

100%
Sakr N.
Journal of Plant Protection Research
|
2019
|
tom 59
|
nr 4
6
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Components of quantitative resistance in barley plants to Fusarium head blight infection determined using three in vitro assays

100%
Sakr N.
Journal of Plant Protection Research
|
2018
|
tom 58
|
nr 2
Quantitative resistance in barley to four Fusarium head blight (FHB) species was investigated in vitro. Nine components involved in three assays (detached leaf, modified Petridish and seedling tests) were compared on two widely grown Syrian barley cultivars: Arabi Aswad (AS) and Arabi Abiad (AB). On AB, inoculation with FHB species resulted in a significantly shorter latent period and larger lesion length of detached leaf inoculation, more standardized area under disease progress curve (AUDPCstandard) of modified Petridish inoculation and a higher percentage of infected seedlings of pin-point inoculation than on AS. The latent period of AB was 14.89% less than AS, lesion length of AS was 6.01% less than AB, AUDPCstandard of AS was 17.07% less than AB and the percentage of infected seedlings of AS was 4.87% less than AB. Inoculation with FHB species resulted in no significant differences in the other five components measured: incubation period of detached leaf inoculation, germination rate reduction and coleoptile length reduction of modified Petridish inoculation, percentage of infected seedlings of foliar-spraying inoculation and lesion length of clip-dipping inoculation. AS was more resistant to in vitro FHB infection than AB. The latent period and AUDPCstandard recorded the highest values compared with the lowest values for lesion length and percentage of infected seedlings. It seems that measurement of the latent period and AUDPCstandard may be useful in identifying barley cultivars which are highly susceptible or resistant to FHB at early stages.
7

Analyzing the influence of qualitative resistance selection pressure on variation of aggressiveness in Plasmopara halstedii

39%
Sakr N., Labrouhe D., Walser P., Ducher M., Delmotte F., Tourvieille J., Vear F.
Journal of Plant Protection Research
|
2011
|
tom 51
|
nr 2
Variation of aggressiveness in populations of race 710 of Plasmopara halstedii [(Farl.) Berl. et Toni] (sunflower downy mildew) was measured under different strategies of qualitative resistance selection pressure: mixture, alternation and monoculture of major resistance genes in comparison with a population under no selection pressure. Two sunflower lines showing different levels of quantitative resistance were used to measure four aggressiveness criteria: percentage infection, latent period, sporulation density and reduction of hypocotyl length. P. halstedii strains multiplied under varietal mixtures presented the greatest sporulation densities and shortest hypocotyl lengths, those multiplied under alternation presented a reduced latent period and shorter hypocotyl lengths compared with those not influenced by selection pressure. There were no significant differences between populations multiplied under monoculture of resistance genes and those under no selection pressure. These changes appear as being linked to the number of infected plants present. The results suggested that the method of Pl gene management affects aggressiveness because it determines the number of susceptible plants harbored by the parasite.
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