Abstract
The influence of short and long day length on the expression of qualitative and quantitative resistance to Phytophthora infestans in potato was studied. The incompatible interaction was tested for available set of isolates avirulent in greenhouse conditions to potato Black’s differentials possessing the genes: R2, R5, R6, R8, R9, R10, and standard potato cultivar Tarpan (no known R gene). The avirulent isolates either were completely avirulent regardless of plant growing conditions, or they infected leaflets of these differentials more frequently when plants were exposed previously to short day conditions than to long day conditions. This study highlights the importance of day length, among many other factors which are controlled, in testing the expression of the virulence of P. infestans isolates. In compatible interactions, when quantitative resistance was evaluated in differentials with gene R1, R3, R4, R7, R11, and potato cultivar Craigs Royal (no known R gene), stronger infection expressed by lesion growth rate, as well as stronger sporulation, were observed on potato leaflets of plants exposed to short day for 6–7 weeks before inoculation. The analysis of variance revealed a significant contribution to variation in lesion growth rate of day length, genotype, as well as day length by genotype interaction. Significant influence of isolate, and genotype, but not day length, on the expression of the incubation period was found. The results indicate the necessity of evaluating components of partial resistance present in potato lines used in breeding potato resistant to P. infestans in destined day length growing conditions.
Highlights
The most economically important potato disease is late blight, caused by Phytophthora infestans, which results in 16 % of global yield losses and annual costs of global control and damage in more than €109 (Haverkort et al 2008, 2009), as well as in environmental and economical losses due to chemical control
In compatible interactions, when quantitative resistance was evaluated in differentials with gene R1, R3, R4, R7, R11, and potato cultivar Craigs Royal, stronger infection expressed by lesion growth rate, as well as stronger sporulation, were observed on potato leaflets of plants exposed to short day for 6–7 weeks before inoculation
The R5 plants grown in short day (SD), long day (LD), and GH conditions did not show any symptoms of infection after inoculation with 6 P. infestans isolates
Summary
The most economically important potato disease is late blight, caused by Phytophthora infestans, which results in 16 % of global yield losses and annual costs of global control and damage in more than €109 (Haverkort et al 2008, 2009), as well as in environmental and economical losses due to chemical control. Qualitative resistance, conferred by R-gene(s), according to the gene-for-gene model (Flor 1971), when effector-triggered immunity is activated, resulting in the hypersensitive response (HR) (Kamoun et al 1999; Jones and Dangl 2006). This kind of interaction is called incompatible, and the isolate avirulent, when P. infestans pathogen secreted RXLR effectors that include. The virulence of P. infestans isolates assessed on differential plants grown in late autumn was more complex than virulence assessed on plants in summer It is evaluated in qualitative manner, plants can be either infected or not infected, and the isolate virulent or avirulent, respectively
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