Studies towards late blight control in potato

Abstract The oomycete Phytophthora infestans, which causes the devastating late blight disease of potato, is notorious for developing resistance to conventional control strategies (fungicide application and resistance breeding by introgression of R gene). To increase our tool box of disease management strategies available to combat P. infestans, there is a need to explore several new approaches that can lead to more durable solutions to control late blight disease. Using the potato-P. infestans pathosystem, different approaches were used in this thesis with an aim to enhance potato defence and find new resistance sources to P. infestans. In the first approach, exogenous application of a new natural agent, sugar beet extract (SBE), resulted in significant reduction of the size of the infection lesions. The pattern was similar to that seen with application of a known defence-inducing compound, β- aminobutyric acid (BABA). SBE triggered pathogenesis-related protein production with no toxic effect on pathogen growth from SBE was noted, which suggests that the protection conferred by SBE is via induced resistance. BABA is a non-protein amino acid that was shown to induce resistance in different plant species and against various pathogens. However, its mechanism of induced resistance (IR) activation in potato to P.infestans is unclear. Thus, in the second approach, a proteomic and transcriptomic study was conducted in an attempt to unravel the mechanism of BABA-IR in potato. It became clear from our study that BABA results in direct activation of several hormonerelated pathways and defence-related proteins. In the third approach, a constitutively activated defence was discovered in one Phytophthora-resistant potato clone (out of two investigated), which could be an interesting starting material in resistance breeding. In the fourth approach, engineering potato plants by in planta expression of pathogen-associated molecular patterns (Pep13 and flg22) resulted in significant reduction of late blight severity, which could be a suitable strategy to alleviate the severity of plant diseases. An integrated pest management approach, including reduction of the use of the fungicides, is one of the recommendations of the recent EU directive. Thus, it is anticipated that combining induced resistance principle and/or a properly designed transgenic approach with conventional control strategies can reduce fungicide inputs and provide a more efficient and sustainable solution for late blight problem

Molecular and immunological methods to confirm toxiginicity (microcystin production) of westiellopsis prolifica isolated from Tigris River - Iraq

Several toxigenic cyanobacteria produce the cyanotoxin (microcystin). Being a health and environmental hazard, screening of water sources for the presence of microcystin is increasingly becoming a recommended environmental procedure in many countries of the world. This study was conducted to assess the ability of freshwater cyanobacterial species Westiellopsis prolifica to produce microcystins in Iraqi freshwaters via using molecular and immunological tools. The toxigenicity of W. prolifica was compared via laboratory experiments with other dominant bloom-forming cyanobacteria isolated from the Tigris River: Microcystis aeruginosa, Chroococcus turigidus, Nostoc carneum, and Lyngbya sp. significant expression of mcyE gene and microcystin production was most evident in W. prolifica. Contrary to the prevailing concept that M. aeruginosa is a main microcystin producer in freshwaters around the world, no significant microcystin production was observed with this species throughout the time points studied in our laboratory methods. As for C. turigidus, N. carneum and Lyngbya sp., neither mcyE expression nor microcystin production was significant. Data from mcyE expression by RT-qPCR were generally in agreement with those obtained from microcystin quantification by ELISA. Interestingly, W. prolifica, which showed clear microcystin-producing ability in this study and which was not reported before in the literature to produce microcystin, can be added as a new microcystin producer to the list of toxigenic cyanobacteria

Paranoid potato : phytophthora-resistant genotype shows constitutively activated defense

Phytophthora is the most devastating pathogen of dicot plants. There is a need for resistance sources with different modes of action to counteract the fast evolution of this pathogen. In order to better understand mechanisms of defense against P. infestans, we analyzed several clones of potato. Two of the genotypes tested, Sarpo Mira and SW93-1015, exhibited strong resistance against P. infestans in field trials, whole plant assays and detached leaf assays. The resistant genotypes developed different sizes of hypersensitive response (HR)-related lesions. HR lesions in SW93-1015 were restricted to very small areas, whereas those in Sarpo Mira were similar to those in Solanum demissum, the main source of classical resistance genes. SW93-1015 can be characterized as a cpr (constitutive expressor of PR genes) genotype without spontaneous microscopic or macroscopic HR lesions. This is indicated by constitutive hydrogen peroxide (H₂O₂) production and PR1 (pathogenesis-related protein 1) secretion. SW93-1015 is one of the first plants identified as having classical protein-based induced defense expressed constitutively without any obvious metabolic costs or spontaneous cell death lesions

Proteomics and transcriptomics of the BABA-induced resistance response in potato using a novel functional annotation approach

Please site as follows:Bengtsson, T. et al. 2014. Proteomics and transcriptomics of the BABA-induced resistance response in potato using a novel functional annotation approach. BMC Genomics, 15(1):315, doi:10.1186/1471-2164-15-315.The original publication is available at http://www.biomedcentral.com/1471-2164/15/315Abstract Background Induced resistance (IR) can be part of a sustainable plant protection strategy against important plant diseases. β-aminobutyric acid (BABA) can induce resistance in a wide range of plants against several types of pathogens, including potato infected with Phytophthora infestans. However, the molecular mechanisms behind this are unclear and seem to be dependent on the system studied. To elucidate the defence responses activated by BABA in potato, a genome-wide transcript microarray analysis in combination with label-free quantitative proteomics analysis of the apoplast secretome were performed two days after treatment of the leaf canopy with BABA at two concentrations, 1 and 10 mM. Results Over 5000 transcripts were differentially expressed and over 90 secretome proteins changed in abundance indicating a massive activation of defence mechanisms with 10 mM BABA, the concentration effective against late blight disease. To aid analysis, we present a more comprehensive functional annotation of the microarray probes and gene models by retrieving information from orthologous gene families across 26 sequenced plant genomes. The new annotation provided GO terms to 8616 previously un-annotated probes. Conclusions BABA at 10 mM affected several processes related to plant hormones and amino acid metabolism. A major accumulation of PR proteins was also evident, and in the mevalonate pathway, genes involved in sterol biosynthesis were down-regulated, whereas several enzymes involved in the sesquiterpene phytoalexin biosynthesis were up-regulated. Interestingly, abscisic acid (ABA) responsive genes were not as clearly regulated by BABA in potato as previously reported in Arabidopsis. Together these findings provide candidates and markers for improved resistance in potato, one of the most important crops in the world.Publishers' Versio