We have known for around 4 decades that soil, decaying vegetation, and plant surfaces harbor organic ice-nucleating particles (INP) and that their abundance and high temperature of activity suggest they are significant sources of atmospheric ice nuclei (1-8). The focus of more recent research has been to elucidate their identities, reservoirs, and emissions to and role, if any (9), in the troposphere (10-22).DeMott and Prenni (23) identified key outstanding questions regarding the role of biogenic INP in cloud and precipitation processes. These included whether they are the sole source of natural atmospheric ice nucleators warmer than about Ϫ15°C, whether they are sufficiently abundant to trigger precipitation directly and/or via secondary ice multiplication, which operates principally in the range of Ϫ3 to Ϫ8°C (24,25,26), whether there are large seasonal and regional variations in their emissions, and whether their numbers can be defined and their sources identified. This work reports progress toward answering the first and last priorities through the development and application of a quantitative PCR (qPCR) test for the ice nucleation-active (INA) bacteria, the abundant and highly active source of biological INP (12).To date, around a dozen species of INA bacteria have been identified, isolated mainly from plant surfaces. They are spread among three orders of the Gammaproteobacteria and include Pseudomonas syringae, Ps. fluorescens, Pantoea agglomerans, and

Buried feral rye seeds were rapidly depleted in soil in the first year due to in situ germination. Less than 1% of the viable seeds persisted after 45 mo of burial. Although after 5 yr, a small number of seedlings still emerged, soil seedbank decline was rapid when seed production was prevented. A low level of induced dormancy was detected and may explain the small populations of feral rye that persisted. Seed and seedling population shifts were large over a 5-yr period and were related to environmental conditions. Tillage or chemical control of feral rye in the fallow period reduced populations compared to the untreated weedy check. Moldboard plowing provided the greatest feral rye control compared to shallow tillage and chemical fallow. Feral rye seedbank populations rebounded following a wet final year of the study. These results help explain feral rye persistence in a wheat–fallow agroecosystem by the persistence of a small portion of the seedbank and by large seed inputs into the system during environmentally favorable years. Feral rye reduced wheat yield as much as 92% and represented up to 73% contamination in harvested wheat.

was less effective than the strobilurins for season-long RRCR management (P ::; 0.05).

No abstract

Genetic resistance to Quinone outside inhibitor (QoI) and benzimidazole fungicides may be responsible for a recent decline in efficacy of chemical control management strategies for Cercospora leaf spot (CLS) caused by Cercospora beticola in Michigan sugarbeet (Beta vulgaris) fields. The target genes and fungicide resistance mutations are known for these two fungicides. Based on this, two standard polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assays were developed to detect the G143A and E198A point mutations in the fungal mitochondrial cytochrome b and the β-tubulin genes, respectively. These mutations confer a high level of resistance to either QoI or benzimidazole fungicides. The presence of the G143A and E198A mutations was monitored within C. beticola populations recovered from Michigan sugarbeet production fields collected in 2012. Both the QoI-resistant cytochrome b allele and the benzimidazole-resistant β-tubulin allele were detected directly from leaf tissue following a PCR-RFLP assay. Using either detection assay, the G143A and E198A mutations were detected in over 90% of the 118 field samples originating from Michigan sugarbeet production under fungicide management programs for CLS control. Monitoring of the G143A and E198A mutations in fields located in 9 counties and 58 townships indicated that the mutations were widespread in Michigan sugarbeet production areas. The PCR-based assays used and developed in this study were effective in detecting the presence of the G143A and E198A mutations in C. beticola field populations from Michigan.