W. F. Kwolek

Interactions of a fungal thioglucoside glucohydrolase and cruciferous plant epithiospecifier protein to form 1-cyanoepithioalkanes: implications of an allosteric mechanism

Abstract Allylglucosinolate is converted to 1-cyano-2,3-epithiopropane by interaction of the thioglucoside glucohydrolase from the fungus Aspergillus sydowi QM 31c and the epithiospecifier protein from Crambe abyssinica . The kinetic evidence presented supports the hypothesis that the epithiospecifier protein interacts with thioglucoside glucohydrolase in an allosteric manner.

A Readability Survey of Technical and Popular Literature.

Study indicates Fog Index of 11 is normal for popular literature. Data suggest Fog Index has increased by 2 during the past 20 years.

Aflatoxin contamination of maize kernels before harvest

Two maize (Zea mays L.) hybrids with varying degrees of resistance to damage by corn earworm (CEW) (Heliothis zea Boddie) were grown in Iowa, Georgia, and Missouri. Treatments included: introduction of Aspergillus flavus Link ex. Fr. spores onto newly-emerged silks, application of a fungicide as an aqueous spray onto test ears during the first three weeks after flowering, infestation of ears with CEW eggs, and combinations of these variables. CEW larvae were collected from developing ears and examined for the presence of internal A. flavus group propagules. Aflatoxin levels were determined in mature kernels. Toxin concentrations exhibited a distinct regional variation with relatively high levels in Georgia samples, intermediate concentrations in Missouri kernels and low levels in Iowa samples. No treatment effects were noted in Georgia samples but introduction of A. flavus and CEW increased toxin accumulation in Missouri kernels. Although the CEW-susceptible hybrid exhibited a trend towards increased damage by the insect, no treatment-related differences were observed in the presence of the fungus in larvae or in aflatoxin contamination. Fungicide applications did not significantly reduce aflatoxin levels in mature kernels.

Aflatoxin accumulation in preharvest maize kernels: Interaction of three fungal species, european corn borer and two hybrids

SummaryThe interaction was studied among: 1) developing maize kernels (Zea mays L.); 2) European Corn Borer (ECB) (Ostrinia nubilalis Hubner); 3) and three fungal species,Aspergillus flavus Lk. ex Fr.,Penicillium oxalcium Currie and Thom, andFusarium moniliforme Sheld. Two hybrids with varying degrees of resistance to ECB stalk damage were grown in Iowa, Georgia, and Missouri in 1980. One-half of the plots were hand-infested with ECB egg masses. Fungal spores of individual isolates or combinations of the three species were introduced into the silk channels of developing ears in designated plots. ECB larvae were subsequently collected from developing ears. A higher incidence ofA. flavus group isolates was observed in ECB larvae collected from ears that had been inoculated withA. flavus than from insects collected from control ears. Although the resistant hybrid exhibited reduced ECB stalk damage compared with the susceptible variety, no consistent pattern of hybrid effect on the association betweenA. flavus and ECB was observed at all three locations. Differences in aflatoxin B1 levels in mature kernels from the three locations ranged from 8 ppb in Iowa samples to 419 ppb in Missouri kernels. Conditions during crop development at the Missouri location were particularly conducive to elevated presence ofA. flavus propagules in ECB larvae, increased ECB-mediated stalk damage, and greater toxin concentration in mature kernels.

Oxygen concentration in larval hemolymph of the Japanese beetle, Popillia japonica, infected with Bacillus popilliae

Abstract A polarographic method for measuring dissolved oxygen was used to follow changes during development of “milky disease” in larvae of the Japanese beetle, Popillia japonica . The dissolved oxygen of hemolymph of apparently healthy third-instar larvae in one group analyzed was equivalent to 33.4% to 42.0% saturation of 0.25 M KCl (0.078 to 0.100 μmoles/ml of hemolymph, 95% confidence limits). The concentration of oxygen was significantly lower early in the infection when only vegetative cells of Bacillus popilliae were present in the hemolymph. When both vegetative and spore forms were present, the oxygen level approached that of the uninfected group. Infection was initiated by feeding spores at the rate of 1–10 million spores/g of soil. At this level, 20% of the larvae became infected.

The effect of European red mite, Panonychus ulmi, on chlorophyll content and chlorophyll a/b ratios of apple, malus domestica borkh., leaves in a growth chamber study (acarina: tetranychidae)

Abstract The effect of European red mite feeding on the total chlorophyll content and the chlorophyll a/b ratios on 5 selections of apple were determined using potted grafts. The study was conducted in a growth chamber with initial infestation levels of 0, 30, 60 or 120 mites/graft, respectively. Significant differences (P< .05) were found among selections in the number of mites following infestation. Selection 2175-7 supported the fewest and selection 1769-3 had the most mites. In the presence of mites leaf chlorophyll content decreased with time and total chlorophyl content was inversely related to the chlorophyll a/b ratios. Pre-infestation chlorophyll values were not significantly different among selections, but they were lower (P< .05) after the 28th day of infestation and thereafter when mites were present. A recovery of leaf chlorophyll content after the removal of mites was not evident. The results suggested that chlorophyll changes due to European red mite feeding were different between resistant...

Rate of oxygen uptake of healthy and diseased larvae of the Japanese beetle

Abstract Conventional Warburg vessels were used to obtain oxygen uptake data on healthy and milky diseased larvae of the Japanese beetle ( Popillia japonica ). The mean Q O 2 O 2 live larvae (LL) and 95% confidence limits were as follows: healthy third-instar larvae, 0.392 ± 0.047; milky third-instar larvae, 0.312 ± 0.050; refrigerated third-instar larvae, 0.156 ± 0.048; and early pupae, 0.332 ± 0.058. Repeated determination of Q O 2 O 2 LL on single larvae over a 6-hr period resulted in steadily decreasing values. No significant correlation existed between oxygen uptake and the dissolved oxygen content of the hemolymph. Injury to larvae caused by insertion of a polarograph needle for dissolved oxygen determination decreased Q O 2 O 2 LL values. After 1 day the rate of oxygen uptake was seen to return to the initial level. Regression analysis failed to establish a correlation between the concentration of microorganisms in diseased thirdinstar larvae and Q O 2 O 2 .

A greenhouse study of the response of a scab, Venturia inaequalis (Cke) wint., resistant apple, Malus domestica (Borkh), selection to european red mite, Panonychus ulmi (Koch), infestation

Abstract An apple scab, resistant selection, 1569-100 with field resistance to powdery mildew and fireblight, growing on EMXXVI rootstock of Malus domestica (Borkh) in the greenhouse, was artifically infested with European red mite (ERM), Panonychus ulmi (Koch) and evaluated for damage. In the first study (1984–1985) one side of the tree was treated with acaricides and the other side untreated, and 17 randomly selected branches were sampled from each side. In the second study (1986–87), the tree was divided into quadrants and 10 randomly selected branches within each quadrant were used for application of the treatments. We induced ERM infestations in the first year of each study using dormant eggs in 1983 and live ERM in 1986. Significant differences (P < 0.05) in total numbers of ERM that developed from dormant eggs were found in 1984, between the untreated and acaricide treated sides of the tree. The branches on the untreated side were significantly shorter (P < 0.05) than those of the treated on two of...