Effect of physio-chemical seed treatments on opium poppy downy mildews caused by Peronospora meconopsidis and P. somniferi

A Quantitative Real-Time PCR Method to Detect the Quinoa Downy Mildew Pathogen, Peronospora variabilis

Quinoa downy mildew, caused by Peronospora variabilis, is the most devastating disease of quinoa globally. Rapid, sensitive diagnostic methods are needed to detect and quantify this pathogen in seeds and plant tissue. A hydrolysis probe-based quantitative real-time PCR (qPCR) assay including a competitive internal control was developed for P. variabilis detection. This assay could detect as low as 20 ag of DNA or approximately 25 internal transcribed spacer (ITS) copies per reaction with efficiencies ranging from 93.9 to 98.2%. No nontarget amplification was observed when tested against DNA from other downy mildew pathogens and related oomycetes. P. variabilis strains from multiple countries were detected using this assay. The assay was successfully applied to quantify the pathogen in quinoa seeds from a field trial conducted in the state of Washington. Downy mildew disease was recorded on all 14 genotypes, with the genotypes 104.88 and 106.49 recording the highest area under the disease progress curve values (mean ± SE; 3,236 ± 303 and 2,851 ± 198, respectively) and J6 and Dutchess recording the lowest (441 ± 107 and 409 ± 129, respectively). Seed washes obtained from field samples were subjected to the qPCR assay, and the pathogen was detected in all samples. The highest pathogen ITS copy number was recorded with 106.49 (194,934 ± 38,171), and the lowest was observed in Pasto (5,971 ± 1,435) and Riobamba (9,954 ± 4,243). This qPCR assay could lead to improved detection and quantification of P. variabilis as well as increased understanding of quinoa-P. variabilis interactions and epidemiology.

Cellulose-Based Photothermal Coating: A Sustainable Solution for Seed Protection and Long-Term Grain Storage

High-output modern agriculture based on synthetic chemicals (biocides, pesticides, and fertilizers) feeds the growing global population. To completely abandon the use of pesticides and fertilizers will undoubtedly cause a severe food crisis worldwide, and sustainable alternative solutions are urgently demanded to stop biocides and fertilizers overuse. Herein, a versatile and green strategy is proposed for seed protection and long-term storage of grains using a cellulose-based photothermal coating (PDA NPs@Cell-N+) that consists of photothermal polydopamine nanoparticles (PDA NPs) and a positive-charged cellulose derivative (Cell-N+) to eradicate seed-borne bacteria and fungi simply under infrared irradiation. In vitro and in vivo assays and the seedling-stage phenotypes of mung bean (Vigna radiata) suggest that pathogenic microbes, including the tough Aspergillus flavus (inhibition ratio >99%), can be efficiently eliminated by photothermal therapy. Thus, the seed-borne diseases of mung beans can finally be prevented. Owing to excellent solubility and biocompatibility, the PDA NPs@Cell-N+ coating can be washed off and recycled without food safety concerns. PDA NPs@Cell-N+ can be a nature-based solution for seed protection and long-term grain storage.