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Late blight caused by Phytophthora infestans is an economically important disease of potato and tomato worldwide. In Canada, an increase in late blight incidence and severity coincided with changes in genetic composition of P. infestans. We monitored late blight incidence on tomato and potato in Pacific western and eastern Canada between 2019 and 2022, identified genotypes of P. infestans, and examined their population genetic diversity. We identified four major existing genotypes US11, US17, US8, and US23 as well as 25 new genotypes. The US11 genotype was dominant in Pacific western Canada, accounting for 59% of the total population. We discovered the US17 genotype for the first time in Canada. We revealed a higher incidence of late blight and quite diverse genotypes of P. infestans in Pacific western Canada than in eastern Canada. We found high genetic diversity of P. infestans population from Pacific western Canada, as evidenced by the high number of multilocus genotypes, high values of genetic diversity indices, and emergence of 25 new genotypes. Considering the number of disease incidence, the detection of diverse known genotypes, the emergence of novel genotypes, and the high number of isolates resistant to metalaxyl-m (95%) from Pacific western Canada, the region could play a role in establishing sexual recombination and diverse populations, which could ultimately pose challenges for late blight management. Therefore, continuous monitoring of P. infestans populations in Pacific western region and across Canada is warranted. Key points: • Genotypes of P. infestans in Pacific western were quite diverse than in eastern Canada. • We discovered US17 genotype for the first time in Canada and identified 26 novel genotypes. • Approximately 95% of P. infestans isolates were resistant to metalaxyl-m. [ABSTRACT FROM AUTHOR]

Proper diagnosis of the causal agents and their characterization are critical steps in the management of bacterial wilt of tomato and other solanaceous vegetable crops. As the species and phylotypes of Ralstonia are different in different geographical regions, it is important to be able to identify the phylotypes present locally quickly and reliably when identifying sources of resistance to bacterial wilt and when deploying host resistance in different regions. Traditional methods for diagnosis and characterization of the causal agents of bacterial wilt require several steps including pathogen isolation from the infected tissues, culturing in a growth media, genomic DNA extraction from the pathogen culture, and few additional steps for molecular identification. In this study, we used a multiplex PCR method to identify the causal species/phylotypes of the pathogen trapped directly from infected plant tissue on FTA (Flinder Technology Associates) cards. Previously characterized R. pseudosolanacearum strain Pss4 (phylotype I) and R. solanacearum strain Pss1632 (phylotype II) separately were inoculated in tomato and eggplant seedlings. Bacterial ooze either directly squeezed from infected plants or streamed in water or 70% ethanol was directly applied on FTA cards and the samples were amplified using a multiplex polymerase chain reaction (PCR) assay. We evaluated four standard methods for processing bacterial wilt samples on FTA cards, which were rapid, sensitive, and reliable for the identification of the species and phylotypes of R. solanacearum complex. These methods will be useful for the characterization/identification of R. solanacearum complex species and phylotypes from diverse locations worldwide since as yet there is no restriction and no import permit is required for the international movement of bacterial wilt sample DNA immobilized and preserved on FTA cards. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) is a devastating disease in wheat throughout the world. FHB resistance consists of two components: resistance to initial infection (type I) and resistance to spread within infected spikes (type II). Current wheat breeding programs for FHB focus on type II resistance, which limits pathogen spread but may not be sufficiently durable. To combine type I with existing type II resistance, 113 F9-derived recombinant inbred lines (RILs) were developed from a cross between three wheat genotypes Frontana, W9207, and Alsen. The RILs were evaluated for resistance to initial infection, FHB spread within spike, kernel damage, and deoxynivalenol (DON) content in two independent greenhouse experiments in 2006 and 2007. Among the 113 RILs, 20% lines showed ≤10% initial disease severity (IDS) and ≤11 to 30% final disease severity (FDS), and 19% had DON content ≤5 μg/g. Approximately 11% of the RILs showed tendency of higher resistance (as exhibited by lower IDS, FDS, and DON content) than the resistant parents. The 42 of the FHB-resistant RILs were analyzed with seven simple sequence repeat (SSR) markers or microsatellites known to be linked to FHB resistance. Approximately half of the RILs had molecular markers linked to both types of FHB resistance indicated the presence of type I and II resistance alleles in the RILs. The resistant RILs identified in this study should be useful for the future improvement of FHB resistance in spring wheat. [ABSTRACT FROM AUTHOR]