John Lydon

Isolation and partial characterization of Bacillus subtilis ME488 for suppression of soilborne pathogens of cucumber and pepper

Environmentally friendly control measures are needed for suppression of soilborne pathogens of vegetable crops in the Republic of Korea. In vitro challenge assays were used to screen approximately 500 bacterial isolates from 20 Korean greenhouse soils for inhibition of diverse plant pathogens. One isolate, Bacillus subtilis ME488, suppressed the growth of 39 of 42 plant pathogens tested. Isolate ME488 also suppressed the disease caused by Fusarium oxysporum f. sp. cucumerinum on cucumber and Phytophthora capsici on pepper in pot assays. Polymerase chain reaction was used to screen isolate ME488 for genes involved in biosynthesis of 11 antibiotics produced by various isolates of B. subtilis. Amplicons of the expected sizes were detected for bacD and bacAB, ituC and ituD, and mrsA and mrsM involved in the biosynthesis of bacilysin, iturin, and mersacidin, respectively. The identity of these genes was confirmed by DNA sequence analysis of the amplicons. Bacilysin and iturin were detected in culture filtrates from isolate ME488 by gas chromatography coupled with mass spectroscopy and by thin layer chromatography, respectively. Detection of mersacidin in ME488 culture filtrates was not attempted. Experiments reported here indicate that B. subtilis ME488 has potential for biological control of pathogens of cucumber and pepper possibly due to the production of antibiotics.

Glyphosate effects on shikimate pathway products in leaves and flowers of velvetleaf

Abstract The effects of sublethal treatments of the herbicide glyphosate [ N -(phosphonomethyl)glycine] on the accumulation of shikimate, hydroxybenzoic acids, and hydroxycinnamic acids in Abutilon theophrasti (velvetleaf) were measured. In newly developing tissues (both leaf and flower), the concentrations of shikimate and protocatechuate were greatly increased by the herbicide, whereas hydroxybenzaldehyde and p -coumarate levels were decreased. During recovery from glyphosate treatment there was a rapid loss of protocatechuate and the levels of other phenolic acids rapidly returned to normal. These indicate that phenolic acid pools in higher plants are regulated and that simple phenolic acids do not accumulate as end products.

UV‐B RADIATION EFFECTS ON PHOTOSYNTHESIS, GROWTH and CANNABINOID PRODUCTION OF TWO Cannabis sativa CHEMOTYPES

The effects of UV‐B radiation on photosynthesis, growth and cannabinoid production of two greenhouse‐grown C. sativa chemotypes (drug and fiber) were assessed. Terminal meristems of vegetative and reproductive tissues were irradiated for 40 days at a daily dose of 0, 6.7 or 13.4 kJ m‐2 biologically effective UV‐B radiation. Infrared gas analysis was used to measure the physiological response of mature leaves, whereas gas‐liquid chromatography was used to determine the concentration of cannabinoids in leaf and floral tissue.

Pseudomonas cannabina pv. cannabina pv. nov., and Pseudomonas cannabina pv. alisalensis (Cintas Koike and Bull, 2000) comb. nov., are members of the emended species Pseudomonas cannabina (ex Šutič & Dowson 1959) Gardan, Shafik, Belouin, Brosch, Grimont & Grimont 1999

Sequence similarity in the 16S rDNA gene confirmed that crucifer pathogen Pseudomonas syringae pv. alisalensis belongs to P. syringae sensu lato. In reciprocal DNA/DNA hybridization experiments, DNA relatedness was high (69-100%) between P. syringae pv. alisalensis strains and the type strain of P. cannabina (genomospecies 9). In contrast, DNA relatedness was low (below 48%) between P. syringae pv. alisalensis and reference strains from the remaining genomospecies of P. syringae including the type strain of P. syringae and reference strain of genomospecies 3 (P. syringae pv. tomato) although the well-known crucifer pathogen, P. syringae pv. maculicola, also belongs to genomospecies 3. Additional evidence that P. syringae pv. alisalensis belongs to P. cannabina was sequence similarity in five gene fragments used in multilocus sequence typing, as well as similar rep-PCR patterns when using the BOX-A1R primers. The description of P. cannabina has been emended to include P. syringae pv. alisalensis. Host range testing demonstrated that P. syringae pv. alisalensis strains, originally isolated from broccoli, broccoli raab or arugula, were not pathogenic on Cannabis sativa (family Cannabinaceae). Additionally, P. cannabina strains, originally isolated from the C. sativa were not pathogenic on broccoli raab or oat while P. syringae pv. alisalensis strains were pathogenic on these hosts. Distinct host ranges for these two groups indicate that P. cannabina emend. consists of at least two distinct pathovars, P. cannabina pv. cannabina pv. nov., and P. cannabina pv. alisalensis comb. nov. Pseudomonas syringae pv. maculicola strain CFBP 1637 is a member of P. cannabina.

Foliar Disease in Fresh-Market Tomato Grown in Differing Bed Strategies and Fungicide Spray Programs

A 3-year field study in central Maryland evaluated foliar disease in fresh-market tomato grown using combinations of four bed strategies and three fungicide programs. Bed strategies included uncovered beds with or without a composted dairy manure amendment or beds covered with black polyethylene or hairy vetch mulch. Fungicide programs included no fungicide, weekly fungicide, or fungicide applications scheduled according to the TOMCAST disease predictor. In plots with hairy vetch-covered beds, early blight caused by Alternaria solani, Septoria leaf spot caused by Septoria lycopersici, and defoliation were lower versus uncovered beds each year. Early blight and defoliation were lower in beds covered with vetch versus polyethylene mulch in 2 of 3 years. Disease severity, defoliation, and marketable yield were similar for the weekly and TOMCAST fungicide programs, with 40 to 50% fewer sprays using TOMCAST. Marketable yield was similar among bed strategies except for higher yields in covered versus uncovered and unamended beds in a relatively wet year and lower yields in vetch versus polyethylene beds in a dry year.