Genetic aspects of potato resistance to phytophthorosis

Phytophthora infestans Mont. de Bary is the main oomycete pathogen of cultivated crops in the family Solanaceae, especially potato (Solanum tuberosum). Because potato is the fourth most cultivated crop worldwide, its annual losses from late blight are tremendous. Studies of the basic mechanisms of interaction between potato and the late blight pathogen not only expand the fundamental knowledge in this area, but also open up new possibilities for regulating these interactions in order to increase resistance to the pathogen. The interaction of potato and the late blight pathogen can be considered from a genetic point of view, and it is interesting to consider both the response of the potato to the colonization process by P. infestans and the change in gene activity in late blight during plant infection. We can also investigate this process by changing the profile of secondary metabolites of the host and the pathogen. In addition to fundamental work in this area, applied work in the form of the development of new preparations for protecting potatoes is of no less importance. This review briefly describes the main stages of studies of potato resistance to late blight, starting almost from the first works. Much attention is paid to key works on changing the profile of secondary metabolites phytoalexins. A separate section is devoted to the description of both qualitative and quantitative characteristics of potato resistance to the late blight pathogen: their contribution to overall resistance, gene mapping, and regulation capabilities. Both types of traits are important for potato breeding: quantitative resistance due to R-genes is quickly overcome by the pathogen, while quantitative trait loci make it possible to create varieties with almost absolute resistance due to the pyramid of effective genes. The latest approaches in molecular biology make it possible to study translatomic profiles, which makes it possible to look at the interaction of potatoes and the late blight pathogen at a different angle. It has been shown that the process of potato colonization affects not only the activity of various genes and the profile of secondary metabolites: proteins­markers of the response to infection from potatoes have also been identified: they are pathogen-bound proteins and plastid carbonic anhydrase. On the part of P. infestans, fungal cellulose synthase proteins and haustorium-specific membrane protein were markers of infection. Thus, the review contains information on the most relevant complex studies of the genetic mechanisms of potato resistance to late blight.

Identification of a Second Asian Soybean Rust Resistance Gene in Hyuuga Soybean

Asian soybean rust (ASR) is an economically significant disease caused by the fungus Phakopsora pachyrhizi. The soybean genes Rpp3 and Rpp?(Hyuuga) confer resistance to specific isolates of the pathogen. Both genes map to chromosome 6 (Gm06) (linkage group [LG] C2). We recently identified 12 additional soybean accessions that harbor ASR resistance mapping to Gm06, within 5 centimorgans of Rpp3 and Rpp?(Hyuuga). To further characterize genotypes with resistance on Gm06, we used a set of eight P. pachyrhizi isolates collected from geographically diverse areas to inoculate plants and evaluate them for differential phenotypic responses. Three isolates elicited different responses from soybean accessions PI 462312 (Ankur) (Rpp3) and PI 506764 (Hyuuga) (Rpp?[Hyuuga]). In all, 11 of the new accessions yielded responses identical to either PI 462312 or Hyuuga and 1 of the new accessions, PI 417089B (Kuro daizu), differed from all others. Additional screening of Hyuuga-derived recombinant inbred lines indicated that Hyuuga carries two resistance genes, one at the Rpp3 locus on Gm06 and a second, unlinked ASR resistance gene mapping to Gm03 (LG-N) near Rpp5. These findings reveal a natural case of gene pyramiding for ASR resistance in Hyuuga and underscore the importance of utilizing multiple isolates of P. pachyrhizi when screening for ASR resistance.