Gary D. Franc

Sea spray aerosol as a unique source of ice nucleating particles

Ice nucleating particles (INPs) are vital for ice initiation in, and precipitation from, mixed-phase clouds. A source of INPs from oceans within sea spray aerosol (SSA) emissions has been suggested in previous studies but remained unconfirmed. Here, we show that INPs are emitted using real wave breaking in a laboratory flume to produce SSA. The number concentrations of INPs from laboratory-generated SSA, when normalized to typical total aerosol number concentrations in the marine boundary layer, agree well with measurements from diverse regions over the oceans. Data in the present study are also in accord with previously published INP measurements made over remote ocean regions. INP number concentrations active within liquid water droplets increase exponentially in number with a decrease in temperature below 0 °C, averaging an order of magnitude increase per 5 °C interval. The plausibility of a strong increase in SSA INP emissions in association with phytoplankton blooms is also shown in laboratory simulations. Nevertheless, INP number concentrations, or active site densities approximated using “dry” geometric SSA surface areas, are a few orders of magnitude lower than corresponding concentrations or site densities in the surface boundary layer over continental regions. These findings have important implications for cloud radiative forcing and precipitation within low-level and midlevel marine clouds unaffected by continental INP sources, such as may occur over the Southern Ocean.

Measurement of Ice Nucleation-Active Bacteria on Plants and in Precipitation by Quantitative PCR

ABSTRACT Ice nucleation-active (INA) bacteria may function as high-temperature ice-nucleating particles (INP) in clouds, but their effective contribution to atmospheric processes, i.e., their potential to trigger glaciation and precipitation, remains uncertain. We know little about their abundance on natural vegetation, factors that trigger their release, or persistence of their ice nucleation activity once airborne. To facilitate these investigations, we developed two quantitative PCR (qPCR) tests of the ina gene to directly count INA bacteria in environmental samples. Each of two primer pairs amplified most alleles of the ina gene and, taken together, they should amplify all known alleles. To aid primer design, we collected many new INA isolates. Alignment of their partial ina sequences revealed new and deeply branching clades, including sequences from Pseudomonas syringae pv. atropurpurea, Ps. viridiflava, Pantoea agglomerans, Xanthomonas campestris, and possibly Ps. putida, Ps. auricularis, and Ps. poae. qPCR of leaf washings recorded ∼108 ina genes g−1 fresh weight of foliage on cereals and 105 to 107 g−1 on broadleaf crops. Much lower populations were found on most naturally occurring vegetation. In fresh snow, ina genes from various INA bacteria were detected in about half the samples but at abundances that could have accounted for only a minor proportion of INP at −10°C (assuming one ina gene per INA bacterium). Despite this, an apparent biological source contributed an average of ∼85% of INP active at −10°C in snow samples. In contrast, a thunderstorm hail sample contained 0.3 INA bacteria per INP active at −10°C, suggesting a significant contribution to this sample.

Cloud activation characteristics of airborne Erwinia carotovora cells

Abstract Several strains of plant pathogenic bacteria, Erwinia carotovora carotovora and E. carotovora atroseptica, were observed to be active as cloud condensation nuclei (CCN). The CCN supersaturation spectra of bacterial aerosols were measured in the laboratory and compared to the activity of ammonium sulfate. Approximately 25%–30% of the aerosolized bacterial cells activated droplets at 1% water supersaturation compared to 80% activation of the ammonium sulfate aerosol. Physical and numerical simulations of cloud droplet activation and growth on bacteria were also performed. Both simulations predict that aerosolized bacteria will be incorporated into cloud droplets during cloud formation. Results strongly support the hypothesis that significant numbers of the tested bacterial strains are actively involved in atmospheric cloud formation and precipitation processes following natural aerosolization and vertical transport to cloud levels.

Seed Certification as a Virus Management Tool

Vegetative or clonal propagation of the potato plant enables tuber borne pathogens to persist from one growing season to the next. Systemic pathogens such as viruses are especially likely to be present in tubers held back for seed. The so-called “running out” or declining productivity of seed tubers that was described over one hundred years ago was eventually found to result from the presence of one or several viruses. Potato seed improvement programs reversed the trend of declining seed productivity and are examples of our earliest attempts at virus management in the seed tuber crop, even before the nature of infectious viruses was known or understood.

Mechanically Transmissable Viruses of Potato

In the early 1900’s farmers, potato breeders, and plant pathologists described problems in potatoes now believed to have been caused by viruses. Terms such as “running out” and “degeneration” were coined to describe the general “loss of vigor,” “loss of stamina,” and “loss of yielding power” associated with tubers harvested from potato cultivars affected by viruses (Krantz and Bisby, 1921; Whipple, 1919). Schulz et al. (1919) and Schulz and Folsom (1920) were able to mechanically transmit a “mosaic dwarf agent,” probably Potato virus Y genus Potyvirus (PVY), but perhaps including Potato virus X genus Potexvirus (PVX), to potato that caused running out. The discovery that several North-American potato cultivars that appeared to be healthy, but were infected with one or more mechanically transmitted viruses, was made by Johnson (1925). He transmitted a virus or viruses latent in potato plants, to several other Solanaceous spp. including tobacco, tomato, and eggplant, which subsequently developed various symptoms including mild mottle, spot-necrosis or ringspot. The virus or one of the viruses he transmitted mechanically eventually came to be known as PVX. Since then, numerous viruses mechanically transmissible to potato have been characterized. Some also have vectors that serve as the principal means of transmission (Table 8.1).

Erratum to: Molecular analysis of Cercospora beticola isolates for strobilurin resistance from the central High Plains, USA

On line 14, the word “developed” is replaced with “used”. The new sentence reads: “We used a PCR-RFLP assay that involved an in vitro digestion using Fnu4HI restriction enzyme for the rapid molecular detection of G143A mutation in the C. beticola population.” Introduction Paragraph 5 On line 2, “develop” is replaced with “use”. The new sentence reads: “The objective was to analyze the C. beticola population for mutations associated with reduced sensitivity to QoI fungicides, and use amolecular diagnostic assay for the rapid detection of strobilurin resistance.” Results Sub-section: “Rapid molecular detection of QoI resistance from C. beticola isolates”. On line 2, the word “led” is replaced with “leading”. The new sentence reads: “PCR products obtained from C. beticola QoI-resistant isolates with a SNP at codon 143 were digested using Fnu4HI restriction enzyme leading to at least three fragments that included 144, 112, and 56 base pairs (bp), whereas QoI-sensitive isolates were digested into at least two fragments that included 264 and 56 bp (Fig. 2).” Discussion (i) Paragraph 4 On line 15, the word “developed” is deleted from the sentence. The new sentence reads: “The PCR-RFLP assay will contribute to the rapid detection of C. beticola QoI resistance, because use of cultural techniques such as “poisonmedia” test can be labor intensive, and require a high expertise as well as several months to obtain results.” (ii) Paragraph 5 On line 5, the word “develop” is replaced with “used”. The new sentence reads: “Herewe used a diagnostic assay that included in vitro digestion with a Fnu4HI restriction enzyme for the rapid molecular detection of G143A mutation associated with C. beticola QoI resistance.” Eur J Plant Pathol (2016) 146:999 DOI 10.1007/s10658-016-1015-6 The online version of the original article can be found at http://dx. doi.org/10.1007/s10658-016-0959-x J. O. Obuya (*) Center for Viticulture and Small Fruit Research, College of Agriculture and Food Sciences, Florida A&M University, 6505 Mahan Drive, Tallahassee, FL 32317, USA e-mail: jamesobuya@yahoo.com W. L. Stump :G. D. Franc Plant Sciences Department-3354, College of Agriculture and Natural Sciences, University of Wyoming, 1000 E. University Ave, Laramie, WY 82071, USA

Mating type idiomorphs distribution and their correlation to benzimidazole-resistance in Cercospora beticola from the Central High Plains region, USA.

Fi 2 P t f ti t idi h di t ib t d b t t i R lt I t d ti g. ercen age o ma ng ype omorp s s r u e y s a e n esu s n ro uc on Central High Plains region Cercospora leaf spot (CLS) caused by Cercospora beticola is . Table-1 Mating type idiomorphs distribution in the Central High Plains region the most important foliar disease of sugar beet worldwide. An . . 100% integrated pest management (IPM) strateg is effecti e for y v 80% CLS suppression Fungicides are widely used for disease Na MAT1 1 MAT1 2 R ti b 2c Pd . i d i l d b i id l Si a o χ suppress on, an nc u e enz m azo es. nce by Year g 60% benzimidazoles are single mode of action systemic fungicides MAT1 2 , 40% resistance can develop quickly in the C. beticola population. 2004 22 17(0 77) 5(0 23)e 3 4 6 55 0 011 Benzimidazole resistance was first reported in C beticola in . . . . . MAT1-1 . 20% 1973 from Greece and later in other regions worldwide 2005 20 17(0.85) 3(0.15) 5.6 9.8 0.002 , . D it d d b i id l i t t i ll t d 0% esp e re uce use, enz m azo e res s ance yp ca y en s 2006 19 14(0 74) 5(0 26) 2 8 4 26 0 039 to persist in the C beticola population Genetic variability and . . . . . CO MT NE WY . . population structure has been reported in C. beticola despite 2007 8 3(0 38) 5(0 62) 0 6 0 5 0 48 th l k d ti b i l Th f Fi 3 P f i idi h di ib d b . . . . . e on y nown repro uc on e ng asexua . ere ore, we g. ercentage o mat ng type omorp s str ute y investigated the correlation between benzimidazole resistance benzimidazole sensitivity in theCentral High Plains region 2008 23 19(0 83) 4(0 17) 4 8 9 8 0 002 . . . . . . and mating type idiomorphs distribution in C. beticola 2009 81 4(0 91) (0 09) 10 6 42 0 population 7 . 7 . . 55. 100% . by State 80%

Hunting the Snark: Identifying the Organic Ice Nuclei in Soils

The contribution of soil organic matter as a potential source of atmospheric ice nuclei (IN) has long been postulated. Rather surprisingly, considering the abundance of IN active at warm temperatures in many soils, it remains unresolved. This research aimed to identify sources of high-temperature, organic IN in a range of Wyoming and Colorado soils. Methods used included physical, chemical and enzymatic tests combined with quantitative PCR to estimate the number of ice nucleation active bacteria. All soils contained 106 to >107 IN active at −10°C. Reductions in IN after heating or digestion with hydrogen peroxide suggested that IN active >−15°C were effectively all organic. Ice nuclei active >−7°C appear to be primarily a mixture of biological macromolecules. At colder temperatures there was a large pool of organic IN that were quite resistant to most physico-chemical challenges.

Laboratory measurements of ice nuclei concentrations from ocean water spray

Preliminary studies of sea spray-produced particles as ice nuclei (IN) are presented. Ice nuclei were found within aerosols produced by realistic wave generation and sea spray production. These IN were less efficient than those typically found in the free troposphere, with number concentrations more or less in accord with previous measurements over remote ocean regions. Nevertheless, sea spray IN could play a role in affecting cloud properties in remote marine regions, and differences in ocean biology could also influence IN efficiency from sea spray generation.

Biological ice nuclei and the impact of rain on ice nuclei populations

With 18% of total US landmass devoted to croplands, farmland is a potentially major source of biogenic particles to the atmosphere. We investigated two farms as potential sources of biological ice nuclei (IN). We found that each of these farms contained abundant INA bacteria on the vegetation; however, airborne ina gene concentrations were typically below detectable limits, demonstrating a disconnect between local vegetative sources and the air above them. The question remains, then, as to how biological IN are released into the atmosphere. In a second study, we investigated how precipitation impacted the concentration and composition of IN. Results from these measurements show that ground level IN concentrations were enhanced during rain events, and that some portion of these IN were biological. In this paper, we present results from both of these studies, and discuss modified measurement techniques aimed at characterizing the often very low number concentrations of biological IN.