Search

To study the influence of thiamethoxam exposure on colony strength and pathogen prevalence, an apiary (5 colonies) was placed in front of a plot sown with winter oilseed rape (wOSR), just before the flowering phase. Before sowing, the seeds were treated with an equivalent application of 18 g thiamethoxam/ha. For comparison, a second apiary (5 colonies) was located in front of a separate 750 m plot sown with untreated wOSR. Dead foragers at the entrance of hives were assessed every 2-3 days throughout the exposure period, while the colony strength (number of combs covered with adult honey bees and brood) and pathogens were monitored each month until the following spring. Foraging on the wOSR crop was confirmed by melissopalynology determination of the corbicular pollen collected periodically, while the chemical analysis showed that exposure to thiamethoxam was mainly through nectar. There was an increase in the accumulation of dead bees in the apiary exposed to thiamethoxam relating with the control, which was coped with an increment of bee brood surface and adult bee population. However, we did not find statistically significant differences between apiaries (α = 0.05) in terms of the evolution of pathogens. We discuss these results under hormesis perspective.

Seed longevity (storability) is an important seed quality trait. High seed quality is important in agriculture, for the industry, and for safeguarding biodiversity as many species are stored as seeds in genebanks. To ensure ex-situ seed survival, seeds are mostly stored at low relative humidity and low temperature. Oxidation is the main cause of seed deterioration in these dry storage conditions. The molecular mechanisms underlying dry seed survival remain poorly understood. Research on seed longevity is hampered by the lack of an experimental ageing method that mimics dry ageing well. Here, we propose the Elevated Partial Pressure of Oxygen (EPPO) method as the best available method to mimic and accelerate dry seed ageing. We have tested seed germination in Arabidopsis thaliana after EPPO storage at two different relative humidity (RH) conditions and confirm the large effect of oxygen and the seed moisture content on ageing during dry storage. Comparative Quantitative trait locus (QTL) analysis shows that EPPO at 55 % RH mimics dry ageing better than the commonly used Artificial Ageing and Controlled Deterioration tests at higher moisture levels., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

Potato cyst nematodes (PCN), such as Globodera rostochiensis and Globodera pallida , are quarantine restricted pests of potato causing major yield and financial losses to farmers. G. rostochiensis was first reported from Kenya's key potato growing area in 2015. We sought to determine the diversity, prevalence and distribution of PCN species across the country by conducting a country-wide survey between 2016 and 2018, which included a more focused, follow-up assessment in three key potato growing counties. A total of 1,348 soil samples were collected from 20 potato growing counties. Information regarding local potato farming practices, potato cultivar use, their diversity and availability was also recorded. PCN cysts were obtained from 968 samples (71.8%) in all the counties surveyed, with Nyandarua County recording the highest PCN field-incidence at 47.6%. The majority of PCN populations, 99.9%, were identified as G. rostochiensis , while G. pallida was recovered from just one field, in a mixed population with G. rostochiensis. Inconsistencies in PCR amplification efficiency was observed for G. rostochiensis using the recommended EPPO primers, compared with ITS primers AB28/TW81, indicating that this protocol cannot be entirely relied upon to effectively detect PCN. Egg density in Nyandarua County varied between 30.6 and 158.5 viable eggs/g soil, with an average egg viability of 78.9 ± 2.8% (min = 11.6%, max = 99.9%). The PCN-susceptible potato cultivar named Shangi was the most preferred and used by 65% of farmers due to its shorter dormancy and cooking time, while imported cultivars (Destiny, Jelly, Manitou, and Markies) with resistance to G. rostochiensis were used by 7.5% of farmers due to unavailability and/or limited access to seeds. Thus, most farmers preferred using their own farm-saved seeds as opposed to purchasing certified seeds. Establishing the distribution and prevalence of PCN and elucidating the local farming practices that could promote the spread of PCN is a necessary precursor to the implementation of any containment or management strategy in the country and ultimately across the region., (Copyright © 2020 Mburu, Cortada, Haukeland, Ronno, Nyongesa, Kinyua, Bargul and Coyne.)

The EU 7th Framework Program provided funds for Quarantine Barcoding of Life (QBOL) to develop a quick, reliable and accurate DNA barcode-based diagnostic tool for selected species on the European and Mediterranean Plant Protection Organization (EPPO) A1/A2 quarantine lists. Seven nuclear genomic loci were evaluated to determine those best suited for identifying species of Mycosphaerella and/or its associated anamorphs. These genes included β-tubulin (Btub), internal transcribed spacer regions of the nrDNA operon (ITS), 28S nrDNA (LSU), Actin (Act), Calmodulin (Cal), Translation elongation factor 1-alpha (EF-1α) and RNA polymerase II second largest subunit (RPB2). Loci were tested on their Kimura-2-parameter-based inter- and intraspecific variation, PCR amplification success rate and ability to distinguish between quarantine species and closely related taxa. Results showed that none of these loci was solely suited as a reliable barcoding locus for the tested fungi. A combination of a primary and secondary barcoding locus was found to compensate for individual weaknesses and provide reliable identification. A combination of ITS with either EF-1α or Btub was reliable as barcoding loci for EPPO A1/A2-listed Mycosphaerella species. Furthermore, Lecanosticta acicola was shown to represent a species complex, revealing two novel species described here, namely L. brevispora sp. nov. on Pinus sp. from Mexico and L. guatemalensis sp. nov. on Pinus oocarpa from Guatemala. Epitypes were also designated for L. acicola and L. longispora to resolve the genetic application of these names.