Improving host resistance to late blight (Phytophthora infestans) has been a major concern of potato breeders since the Irish famine of 1840s. Since then, a number of late blight resistant potato (Solanum tuberosum L.) cultivars have been developed using both conventional and molecular techniques. However, resistance to late blight did not last long and broke down due to the emergence of more virulent races of Phytophthora infestans. This perspective paper presents the status of sources of resistance to late blight, defence mechanism of host against the pathogen and late blight resistance genes mapped, cloned, and transferred to cultivated potato. Considerable progress has been made in all aspects of breeding potato for resistance to late blight. However, a critical appraisal of the status of potato breeding for resistance to late blight suggests the continued need to identify new sources of resistance, transfer of resistance genes from diverse sources and stacking them in maximum number into individual plants. Other breeding strategies to combat this dreaded disease are also discussed.

Improving host resistance to late blight (Phytophthora infestans) has been a major concern of potato breeders since the Irish famine of 1840s. Since then, a number of late blight resistant potato (Solanum tuberosum L.) cultivars have been developed using both conventional and molecular techniques. However, resistance to late blight did not last long and broke down due to the emergence of more virulent races of Phytophthora infestans. This perspective paper presents the status of sources of resistance to late blight, defence mechanism of host against the pathogen and late blight resistance genes mapped, cloned, and transferred to cultivated potato. Considerable progress has been made in all aspects of breeding potato for resistance to late blight. However, a critical appraisal of the status of potato breeding for resistance to late blight suggests the continued need to identify new sources of resistance, transfer of resistance genes from diverse sources and stacking them in maximum number into individual plants. Other breeding strategies to combat this dreaded disease are also discussed.

Ralstonia solanacearum, the causal agent of bacterial wilt, is one of the most devastating bacterial diseases worldwide. In potatoes and many other commercial species such as tomato, banana, plantain, and eggplant, among others, there is a lack of efficient strategies to control this pathogen. Therefore, using resistant cultivars might be the best strategy to prevent this disease. However, breeding for bacterial wilt resistance is challenging since latent infections pose a significant limitation when evaluating resistance to this disease in plant germplasm. Part of the diversity of potato genetic resources is maintained in the Colombian Central Collection (CCC) of potatoes, Corporación Colombiana de Investigación Agropecuaria (Agrosavia). With its 2069 accessions, the CCC is a good source for plant breeding programs. As a first attempt to identify bacterial wilt resistant/tolerant potato sources, 11 commercially available potato varieties were evaluated, representing Andigena and Phureja materials from the CCC. To this end, plants were drench-inoculated with R. solanacearum. This strain was able to cause severe disease in six of the 11 accessions tested. Thus, five highly R. solanacearum-resistant accessions were identified. These results represent a preliminary assessment for identifying bacterial wilt resistance sources that will contribute to establishing a potato breeding program to face this devasting pathogen before it arrives to Colombia. | Papa-Solanum tuberosum

Ralstonia solanacearum, the causal agent of bacterial wilt, is one of the most devastating bacterial diseases worldwide. In potatoes and many other commercial species such as tomato, banana, plantain, and eggplant, among others, there is a lack of efficient strategies to control this pathogen. Therefore, using resistant cultivars might be the best strategy to prevent this disease. However, breeding for bacterial wilt resistance is challenging since latent infections pose a significant limitation when evaluating resistance to this disease in plant germplasm. Part of the diversity of potato genetic resources is maintained in the Colombian Central Collection (CCC) of potatoes, Corporación Colombiana de Investigación Agropecuaria (Agrosavia). With its 2069 accessions, the CCC is a good source for plant breeding programs. As a first attempt to identify bacterial wilt resistant/tolerant potato sources, 11 commercially available potato varieties were evaluated, representing Andigena and Phureja materials from the CCC. To this end, plants were drench-inoculated with R. solanacearum. This strain was able to cause severe disease in six of the 11 accessions tested. Thus, five highly R. solanacearum-resistant accessions were identified. These results represent a preliminary assessment for identifying bacterial wilt resistance sources that will contribute to establishing a potato breeding program to face this devasting pathogen before it arrives 70 Colombia.

Abstract Ralstonia solanacearum, the causal agent of bacterial wilt, is one of the most devastating bacterial diseases worldwide. In potatoes and many other commercial species such as tomato, banana, plantain, and eggplant, among others, there is a lack of efficient strategies to control this pathogen. Therefore, using resistant cultivars might be the best strategy to prevent this disease. However, breeding for bacterial wilt resistance is challenging since latent infections pose a significant limitation when evaluating resistance to this disease in plant germplasm. Part of the diversity of potato genetic resources is maintained in the Colombian Central Collection (CCC) of potatoes, Corporación Colombiana de Investigación Agropecuaria (Agrosavia). With its 2069 accessions, the CCC is a good source for plant breeding programs. As a first attempt to identify bacterial wilt resistant/tolerant potato sources, 11 commercially available potato varieties were evaluated, representing Andigena and Phureja materials from the CCC. To this end, plants were drench-inoculated with R. solanacearum. This strain was able to cause severe disease in six of the 11 accessions tested. Thus, five highly R. solanacearum-resistant accessions were identified. These results represent a preliminary assessment for identifying bacterial wilt resistance sources that will contribute to establishing a potato breeding program to face this devasting pathogen before it arrives to Colombia. | Resumen Ralstonia solanacearum es el agente causal de la marchitez bacteriana de la papa, una de las enfermedades bacterianas más devastadoras a nivel mundial. En la actualidad no hay una buena estrategia de control para esta enfermedad en la papa y en muchas otras especies comerciales tales como tomate, banano, plátano, berenjena, entre otros. Por este motivo, el uso de genotipos resistentes puede ser la mejor estrategia de control contra esta enfermedad. Sin embargo, el mejoramiento genético para la resistencia a la marchitez bacteriana representa un reto muy grande, ya que las infecciones latentes pueden ser una limitante al evaluar los genotipos resistentes a esta enfermedad. Una parte de la diversidad de los recursos genéticos de papa se conserva en la colección central de Colombia (CCC) de la Corporación Colombiana de Investigación Agropecuaria (Agrosavia). La CCC con sus 2069 accesiones es una fuente importante para programas de mejoramiento genético. Como una primera aproximación para la caracterización e identificación de materiales de papa resistentes o tolerantes a la marchitez bacteriana, se evaluaron 11 variedades comerciales de papa, representantes de los grupos Andigena y Phureja de la CCC. Para esto, las plantas se inocularon por empapamiento y se encontró que la cepa de R. solanacearumque se utilizó fue capaz de causar la enfermedad en seis de las once accesiones evaluadas. Por lo tanto, se identificaron cinco genotipos altamente resistentes. Estos resultados son una evaluación preliminar para la identificación de fuentes de resistencia contra R. solanacearum, lo cual contribuirá al establecimiento de un programa de mejoramiento genético de la papa para enfrentar esta devastadora enfermedad antes de que llegue a Colombia.

Plants with innate disease and pest resistance can contribute to more sustainable agriculture. Natural defence compounds produced by plants have the potential to provide a general protective effect against pathogens and pests, but they are not a primary target in resistance breeding. Here, we identified a wild relative of potato, Solanum commersonii, that provides us with unique insight in the role of glycoalkaloids in plant immunity. We cloned two atypical resistance genes that provide resistance to Alternaria solani and Colorado potato beetle through the production of tetraose steroidal glycoalkaloids (SGA). Moreover, we provide in vitro evidence to show that these compounds have potential against a range of different (potato pathogenic) fungi. This research links structural variation in SGAs to resistance against potato diseases and pests. Further research on the biosynthesis of plant defence compounds in different tissues, their toxicity, and the mechanisms for detoxification, can aid the effective use of such compounds to improve sustainability of our food production.