We sequenced and comprehensively analysed the genomic architecture of 98 fluorescent pseudomonads isolated from different symptomatic and asymptomatic tissues of almond and a few other Prunus spp. ...Phylogenomic analyses, genome mining, field pathogenicity tests, and in vitro ice nucleation and antibiotic sensitivity tests were integrated to improve knowledge of the biology and management of bacterial blast and bacterial canker of almond. We identified Pseudomonas syringae pv. syringae, P. cerasi, and P. viridiflava as almond canker pathogens. P. syringae pv. syringae caused both canker and foliar (blast) symptoms. In contrast, P. cerasi and P. viridiflava only caused cankers, and P. viridiflava appeared to be a weak pathogen of almond. Isolates belonging to P. syringae pv. syringae were the most frequently isolated among the pathogenic species/pathovars, composing 75% of all pathogenic isolates. P. cerasi and P. viridiflava isolates composed 8.3 and 16.7% of the pathogenic isolates, respectively. Laboratory leaf infiltration bioassays produced results distinct from experiments in the field with both P. cerasi and P. syringae pv. syringae, causing significant necrosis and browning of detached leaves, whereas P. viridiflava conferred moderate effects. Genome mining revealed the absence of key epiphytic fitness-related genes in P. cerasi and P. viridiflava genomic sequences, which could explain the contrasting field and laboratory bioassay results. P. syringae pv. syringae and P. cerasi isolates harboured the ice nucleation protein, which correlated with the ice nucleation phenotype. Results of sensitivity tests to copper and kasugamycin showed a strong linkage to putative resistance genes. Isolates harbouring the ctpV gene showed resistance to copper up to 600 μg/ml. In contrast, isolates without the ctpV gene could not grow on nutrient agar amended with 200 μg/ml copper, suggesting ctpV can be used to phenotype copper resistance. All isolates were sensitive to kasugamycin at the label-recommended rate of 100μg/ml.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Prevalence of latent infections of the canker-causing fungi
and species of
,
,
,
, and
in young shoots of almond, prune, and walnut trees in California was studied to test the hypotheses that latent ...infections accumulate from current-season shoots to 1-year-old shoots in the orchard and there are distinct associations among pathogen taxa present as latent infections in the same shoot. Samples of newly emerged and 1-year-old shoots were periodically collected in each almond, prune, and walnut orchard for two growing seasons. A real-time quantitative PCR assay was used to quantify latent infection with three parameters: incidence, molecular severity, and latent infection index.
spp. were absent from most samples. For almond,
spp. and
spp. were detected with a maximum incidence >90%, while
and
spp. incidence was <20% in most cases. In prune orchards, the incidence levels of
were >50% in most cases, while those of
spp. and
spp. were 30 to 60% and 30 to 100%, respectively. For walnut, many samplings showed higher incidence in 1-year-old (30 to 80%) than in newly emerged shoots (10 to 50%). Accumulation of latent infection between the two shoot age classes was detected in only a few cases. The percentages of samples showing coexistence of two, three, and four pathogen taxa in the same shoot were 20 to 25, <10, and <5%, respectively. Pairwise associations among pathogen taxa in the same shoot were significant in many cases.
This study was aimed to develop a sequential infrared and hot air (SIRHA) drying method for whole almonds and evaluate its effectiveness on decontamination of almonds. Wet almonds with hull and shell ...were dried using different time-combinations of infrared (IR) radiation and hot air (HA) to determine the optimum drying conditions. Almonds were inoculated with Enterococcus faecium, a surrogate for Salmonella enterica. The SIRHA drying (1h IR at 70 °C and 2h HA) reduced the moisture content of almonds to 7% in 3 h, with a saving of 2 h (40%) of drying time compared with HA drying alone. The population sizes of E. faecium showed the largest size reductions of 4.69 ± 0.71, 1.82 ± 0.39, 1.52 ± 0.31 log CFU/nut on hulls, shells and kernels, respectively, after SIRHA drying combined with tempering (T) (2h IR with 2h T and 1h HA). The peroxide value and free fatty acids content of almond oil samples from all drying treatments were within accepted level for the almond industry.
•SIRHA treatments reduced drying time by 40% compared with hot air drying alone.•SIRHA combined with tempering achieved the significant reduction of E. faecium population sizes on whole almonds.•The quality of SIRHA-dried almond kernels was within the standard range based on oil quality.
Almond canker diseases are destructive and can reduce the yield as well as the lifespan of almond orchards. These diseases may affect the trunk and branches of both young and mature trees and can ...result in tree death soon after orchard establishment in severe cases. Between 2015 and 2018, 70 almond orchards were visited throughout the Central Valley of California upon requests from farm advisors for canker disease diagnosis. Two major canker diseases were identified, including Botryosphaeriaceae cankers and Ceratocystis canker. In addition, five less prevalent canker diseases were identified, including Cytospora, Eutypa, Diaporthe, Collophorina, and Pallidophorina canker. Seventy-four fungal isolates were selected for multilocus phylogenetic analyses of internal transcribed spacer region ITS1-5.8S-ITS2 and part of the translation elongation factor 1-α, β-tubulin, and glyceraldehyde 3-phosphate dehydrogenase gene sequences; 27 species were identified, including 12 Botryosphaeriaceae species,
, five
species,
, four
species, two
species,
, and
. The most frequently isolated species were
,
, and
. Pathogenicity experiments on almond cultivar Nonpareil revealed that
,
, and
were the most virulent. Botryosphaeriaceae cankers were predominantly found in young orchards and symptoms were most prevalent on the trunks of trees. Ceratocystis canker was most commonly found in mature orchards and associated with symptoms found on trunks or large scaffold branches. This study provides a thorough examination of the diversity and pathogenicity of fungal pathogens associated with branch and trunk cankers of almond in California.
The Botryosphaeriaceae family is considered a fungal family that includes pathogens causing latent infection of woody plants, and a number of species were identified as causal pathogens of canker and ...shoot blight diseases. To better understand the process of latent infection of major canker-causing pathogens in woody tissues in different tree crops important in California, shoot and bud samples were randomly collected from four tree crops: almond, dried plum, pistachio, and walnut. The previously developed DNA primers and quantitative real-time PCR (qPCR) assay systems were applied to detect six canker-causing pathogen groups, including
, and species of
,
,
,
, and
The concepts of molecular severity (MS) and latent infection index (LII) were introduced and applied to quantify the latent infection levels for these samples. Variation in incidence of latent infection among pathogen groups was observed, whereas the incidences were relatively low among species of
and
High incidences of
spp. were observed in two dried plum (prune) orchards. Most orchards showed high incidences of
and
spp. and moderate incidences of
spp. Variations in MS were observed among samples of the studied orchards, ranging from 4 to 8. The overall results of LII demonstrated that species of
and
were less important in population development of canker-causing pathogens at the latent phase.
spp. were the most aggressive and had been well developed in populations among the studied tree crops.
spp. became predominant in two of the three dried plum orchards, whereas
and
spp. showed trends of increase in incidence across various tree crops. This study also demonstrated the usefulness of this sensitive qPCR approach in providing evidence of the latent phase of major canker-causing pathogens of stone fruit and nut crops at an early stage of latent infection in woody plant tissues.
BACKGROUND
Insecticide application is essential to control navel orangeworm (Amyelois transitella) in California almond and pistachios. Coverage is difficult because of tree height and applicator ...practices. Studies were conducted to characterize insecticide deposition by both ground and air, and to develop alternatives to the use of water‐sensitive cards to assess spray coverage.
RESULTS
We used almond challenge bioassays to demonstrate that insecticide application failed first in the upper canopy (5.2–6.1 m) when application speed exceeded 2.9 kph. In pistachios, we used filter paper and insecticide extraction from hulls to demonstrate that deposition increased with application volume. Typically, in ground applications, coverage decreased with height, whereas for application by air, coverage was greatest at the top of the canopy (6 m) and decreased as the spray penetrated the canopy. In the best ground applications there was no loss over height. We were able to demonstrate a dose–response relationship for methoxyfenozide using contact toxicity bioassays.
CONCLUSION
Coverage was best at or below the recommended speed of 3.2 kph and improved when water volume increased. There was a 50% loss in insecticide efficacy at the height of 4–4.8 m; we suggest that future monitoring concentrate on this portion of the canopy. The best ground application provided uniform deposition throughout the canopy, whereas the applications by air were most effective in the upper canopy. The use of filter paper can provide information for chemical deposition and enable contact toxicity bioassays, whereas water‐sensitive paper cannot do this. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.
Recovery from pistachio trees of bifenthrin (applied at 864.9 mL/140.3 L) per ha from filter paper placed at 61 cm intervals following aerial application by fixed‐wing aircraft.
Amyelois transitella (Walker) (Lepidoptera: Pyralidae) and Anarsia lineatella Zeller (Lepidoptera: Gelechiidae) are key Lepidoptera pests of almonds in California. Spring insecticide applications ...(early to mid-May) targeting either insect were not usually recommended because of the potential to disrupt natural enemies when broad-spectrum organophosphates and pyrethroids were applied. The registration of reduced risk compounds such as chlorantraniliprole, methoxyfenozide, and spinetoram, which have a higher margin of safety for natural enemies, makes spring (early to mid-May) application an acceptable control approach.We examined the efficacy of methoxyfenozide, spinetoram, and chlorantraniliprole at three spring application timings including the optimum spring timing for both A. lineatella and A. transitella in California almonds. Our study also examined the possibility of reducing larval populations of A. lineatella and A. transitella simultaneously with a single spring insecticide application. There were no significant differences in the field efficacy of insecticides targeting either A. lineatella or A. transitella, depending on application timing for the three spring timings examined in this study. In most years (2009–2011), all three timings for each compound resulted in significantly less A. transitella and A. lineatella damage when compared with an untreated control, though there was some variation in efficacy between the two species. Early to mid-May applications of the reduced-risk insecticides chlorantraniliprole and spinetoram can be used to simultaneously target A. transitella and A. lineatella with similar results across the potential timings.
Unmanaged spray drift from orchard pesticide application contributes to environmental contamination and causes significant danger to farmworkers, nearby residential areas, and neighbors’ crops. Most ...drift control approaches do not guarantee adequate and uniform canopy spray coverage. Our goal was to develop a spray backstop system that could block drifting from the top without any negative impact on spray coverage and on-target deposition. The design included a foldable mast and a shade structure that covered the trees from the top. We used a continuous loop sampling to assess and quantify the effectiveness of spray backstop on drift potential reduction. We also collected leaf samples from different sections of trees to compare on-target deposition and coverage. The results showed that the spray backstop system could significantly (p-Value < 0.01) reduce drift potential from the top (78% on average). While we did not find any statistical difference in overall canopy deposition with and without the backstop system, we observed some improvement in treetops deposition. This experiment’s output suggests that growers may be able to adjust their air-assist sprayers for a more uniform spray coverage without concern about the off-target movement of spray droplets when they employ the spray backstop system.
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