The oomycete pathogen Phytophthora infestans causes late blight disease that severely reduces potato production worldwide. Monitoring the genotypic and virulence dynamics of P. infestans populations is vital for management of late blight. Phytophthora infestans populations in southwestern China diversify in genotypes and virulence, but the most recent status of these populations remains elusive. In this study, 218 isolates collected from six locations in southwestern China from 2019 to 2022 were analyzed for genotypic and virulence dynamics as well as effective management strategies. Phylogenetic analysis of simple sequence repeats-classified multi-locus genotypes (MLGs) revealed that these populations comprise three lineages, of which the EU lineage is dominant. These populations had overcome the resistance mediated by R3a, R3b and Rpi-blb3 and had an increased trend in overcoming the resistance mediated by Rpi-blb2, R8, Rpi-blb1 and Rpi-vnt1.1. The EU lineage consisted of 19 MLGs and the predominant genotype MLG24 significantly contributed to the pathotypic diversity of the EU lineage. In addition, two independent MLG24 isolates, CQ-22-16-1 and CQ-22-20-1, overcame the resistance mediated by all seven resistance genes and were virulent on 30 potato cultivars. Notably, two Solanum candolleanum relatives were highly resistant to these two highly virulent isolates. Furthermore, these two isolates could be controlled by three fungicides. In summary, this study elucidates the genotypic and virulence dynamics of P. infestans populations in southwestern China and provides valuable insights into effective control measures.

Late blight, caused by the oomycete plant pathogen Phytophthora infestans, is a destructive disease that leads to significant yield loss in potatoes and tomatoes. The introgression of disease resistance (R) genes, which encode nucleotide-binding domain leucine-rich repeat-containing receptors (NLRs), into cultivated potatoes, is highly effective in controlling late blight. Here, we generated transgenic 2R and 3R potato lines by stacking R genes Rpi-blb2/Rpi-vnt1.1 and Rpi-vnt1.1/RB/R8, respectively, in the susceptible cv. Desiree background. The resulting 2R and 3R transgenic potato plants showed resistance to highly virulent P. infestans field isolates. We hypothesized that stacking R genes either resulted in up-regulation of a broader range of immune-related genes, or, more importantly, increase in the fold change of gene expression. To test our hypotheses, we performed transcriptome analysis and identified a subset of core immune-related genes that are induced in response to P. infestans in transgenic lines carrying single R genes versus lines carrying stacks of multiple R genes. In our analysis, stacking R genes resulted not only in the induction of a broader range of defense-associated genes but also a global increase in gene expression fold change, caused by the pathogen. We further demonstrated that the calcium-dependent protein kinase 16 (StCDPK16) gene significantly contributed to resistance to a virulent P. infestans strain, in the R gene background, in a kinase activity-dependent manner. Thus, our data suggest that stacking the R genes enhances late blight resistance through modulating the expression of a broader range of defense-related genes and highlights StCDPK16 as a novel player in potato R gene-mediated resistance.

Summary Leucine‐rich repeat receptor‐like kinases (LRR‐RLKs) comprise the largest class of membrane‐localized receptor‐like kinases in plants. Leucine‐rich repeat receptor‐like kinases are key immune sectors contributing to pattern‐triggered immunity (PTI), but whether LRR‐RLK mediates effector‐triggered immunity (ETI) in plants remains unclear. In this study, we evaluated the function of LRR‐RLKs in regulating ETI by using a virus‐induced gene silencing (VIGS)‐based reverse genetic screening assay, and identified a LRR‐RLK named ETI‐dependent receptor‐like kinase 1 (EDK1) required for ETI triggered by the avirulence effector AVRblb2 secreted by Phytophthora infestans and its cognate receptor Rpi‐blb2. Silencing or knockout of EDK1 compromised immunity mediated by Rpi‐blb2 and the cell death triggered by recognition of AVRblb2. NLR‐required for cell death 4 (NRC4), a signaling component acts downstream of Rpi‐blb2, was identified that interacts with EDK1 using the LC–MS analysis and the interaction was further evaluated by co‐immunoprecipitation. EDK1 promotes protein accumulation of NRC4 in a kinase‐dependent manner and positively regulates resistance to P. infestans in Nicotiana benthamiana. Our study revealed that EDK1 positively regulates plant ETI through modulating accumulation of the NLR signaling component NRC4, representing a new regulatory role of the membrane‐localized LRR‐RLKs in plant immunity.

AbstractVarious pathogens from oomycete, fungi, and bacteria kingdoms can infect potato and significantly reduce potato yield. The early diagnosis of potato pathogens is important for tracing disease epidemics and the subsequent disease management. Loop-mediated isothermal amplification (LAMP) is a critical technique for pathogen detection, but available LAMP assays do not effectively meet the requirement of field diagnoses due to complexities including co-infection of different pathogens. Hence, this study aims to develop integrated-LAMP assays (iLAMPs) for simultaneous detection of eight common potato pathogens and apply iLAMPs to pathogen detection in field samples from the four main potato-growing regions of China in 2023. Therefore, eight sets of primers showing gene- and genus-specificity were designed and used for iLAMPs to determine their specificity, sensitivity, and visualization. Subsequently, iLAMPs-mediated pathogen detection revealed that 72.82% of 206 diseased leaves and 84.94% of 239 diseased tubers carry more than one pathogen. The detection rate for each pathogen significantly varies from 1.94 to 65.53% in diseased leaves, and ranges from 26.78 to 52.72% in diseased tubers, respectively. In addition, the detection rate of Phytophthora infestans and Alternaria solani positively correlates in both leaves and tubers, especially for those samples from the southwestern and southern regions. Taken together, iLAMPs developed in this study enables simultaneous detection of eight common potato pathogens from field samples and may have broad applications in early management of potato diseases.

马铃薯晚疫病是由致病疫霉引发的重大毁灭性病害,长期在我国各马铃薯主产区暴发流行,是马铃薯产业发展的重要瓶颈因素.目前大田防控马铃薯晚疫病仍主要依赖化学防控.本文梳理了近年来我国市场防治晚疫病的杀菌剂产品发展趋势,对马铃薯晚疫病化学防控策略与应用现状进行了归纳.结合本课题组近年来的田间调研结果,探讨了我国马铃薯晚疫病防控中的新情况,并对未来化学精准防控的前景进行了展望,提出加快发展病菌致病型和抗药性监测技术,注重新型农药与精准施用技术的源头创新,以期为未来开展马铃薯晚疫病的可持续防控提供新思路.

Phytophthora infestans, the causal agent of the fish Potato Famine in the 1840s, is one of the most destructive crop pathogens that threaten global food security. Host resistance (R) genes may help to control the disease, but recognition by through the gene products can be evaded by newly emerging isolates. Such isolates are dangerous as they may cause disease outbreaks under favorable conditions. However, our lack of knowledge about adaptation in these isolates jeopardizes an apt response to resistance breakdown. Here we performed genome and transcriptome sequencing of HB1501 and HN1602, two field isolates from distinct Chinese geographic regions. We found extensive polymorphisms in these isolates, including gene copy number variations, nucleotide polymorphisms, and gene expression changes. Effector encoding genes, which contribute to virulence, show distinct expression landscapes in P. infestans isolates HB1501 and HN1602. In particular, polymorphisms at multiple effectors required for recognition (Avr loci) enabled these isolates to overcome corresponding R gene based resistance. Although the isolates evolved multiple strategies to evade recognition, we experimentally verified that several R genes such as R8, RB, and Rpi-vra1.1 remain effective against these isolates and are valuable to potato breeding in the future. In summary, rapid characterization of the adaptation in emerging field isolates through genomic tools inform rational agricultural management to prevent potential future epidemics.