Ja. Meyer

Identification of 3(methylthio) propionic acid as a blight-inducing toxin produced by Xanthomonas campestris pv. manihotis in vitro☆

Abstract A toxic substance was extracted by ethyl acetate from a broth culture of Xanthomonas campestris pv. manihotis acidified at pH 4 with 1 n HCl. When infiltrated into cassava leaves the crude extract produced blight symptoms similar to those induced by the bacteria during patho- The toxic substance was purified by gel filtration on a Sephadex G10 column (Pharmacia) and by thin layer chromatography on silica gel 60 (Merck), where it showed a RF of 0·6 using as migration system methanol : chloroform : n-hexane (3 : 2 : 1, v/v). By mass spectrometry, infrared spectroscopy, and C, H, N analyses the purified toxin was identified as 3(methylthio) propionic acid. This identification was confirmed by chemical synthesis. On detached cassava leaves, 3(methylthio) propionic acid gave a toxic effect up to a concentration of 9·9 m m corresponding to 24 μg of pure substance in a 20 μl drop of water.

Detection of 3(methylthio) Propionic-acid in Cassava Leaves Infected By Xanthomonas-campestris Pv Manihotis

The blight inducing toxin 3(methylthio)propionic acid (MTP acid) was detected by gas liquid chromatography in extracts of cassava leaves, naturally or artificially infected by Xanthomonas campestris pv. manihotis . The highest toxin concentration (6 μg g −1 fresh weight) was associated with the appearance and extension of the blight symptoms in artificially infected leaves. Sulphur containing compounds, more volatile than MTP acid, were also observed in necrotic tissues. One of them was identified by peak amplification as thiopropionic acid.

Effects of Selected Insecticides and Herbicides On the Carotene Content of Summer Carrots

Abstract The soil of plots of summer carrot cultures was treated before sowing with one of the insecticides Nexion, Birlane or Dyfonate, or with one of the herbicides Afalon Spezial or Dosanex; the control plots remained untreated. The carrots were harvested at weekly intervals, and their concentration of total carotene was determined. For the carrots grown in soil treated with Nexion, Birlane, Dyfonate or Afalon S, the concentrations of total carotene were always higher than in the controls, the largest difference being about 21%. For carrots grown in the soil treated with Dosanex, the concentration of total carotene was lower than in the control, the largest difference being about 19%.

Cultivar Differences in the Influence of Harvest Date and Cold-storage On the Free Sugars and Acids Contents, and On the Eating Quality of Apples

SummaryDuring the 15-day period around the commercial harvest date of Jonagold apples the total free sugars content did not change, but with later harvest the percentage of sucrose increased from 27 to 30% and that of sorbitol from 7 to 10% but glucose content decreased from 29 to 24%. In Cox’s Orange Pippin apples both the total free sugars content and their distribution did not change with the change of harvest date. Delaying the harvest date did not cause a decrease of free acidity in either cultivar. During cold storage at 1°C (not CA) of Jonagold apples the total free sugars content did not change, but the percentage of sucrose decreased from 27 to 19%, fructose increased from 37 to 41% and glucose from 29 to 32%. During storage at 3.5°C (not CA) of Cox’s Orange Pippin apples the total free sugars content increased but the proportions of the sugars did not change. During cold storage the rate of decrease of free acidity was much less in Jonagold than in Cox’s Orange Pippin, and the eating quality dec...

Effects of Selected Fungicide Treatments On the Sugar Content of Golden Delicious and Jonagold Apples

Abstract Several fungicide treatment schemes were assayed on ‘Golden Delicious’ and ‘Jonagold’ apples. The free sugars (fructose, glucose, sorbitol, sucrose and their total) of freshly harvested apples were measured and compared to those obtained with the corresponding untreated apples (control). With ‘Golden Delicious’, the fungicide treatments generally increased the content of fructose, sucrose and total sugars, but had no effect on the glucose content. With ‘Jonagold’, similar effects were observed, but their intensities generally were lower than in ‘Golden Delicious’; in some cases, the treatments even decreased the sugar content.

Quality of Potatoes Treated With Selected Insecticides and Potato-haulm Killers

SummaryTreatment with aldicarb and demeton-S-methyl had no influence on the dry weight or on the starch or protein contents, but increased the content of ascorbic acid by up to 25%. Diquat, dinoseb and metoxuron had no effect on dry weight or starch content; dinoseb and metoxuron increased the protein and ascorbic acid contents by up to 20%. The effects of the pesticide treatments on the chemical composition of freshly harvested potatoes were maintained during their cold storage.

Effects of Soil Fertilization and of Covering of the Culture With Plastic Film On the Provitamin-a Content of Early Lettuces

SummaryDifferent growing conditions of early lettuces were assayed. Some plots of lettuces were grown covered with a perforated plastic sheet, and other plots were not covered. The soil of some plots was fertilized with a usual N+P+K+S fertilizer used at a normal rate, and the soil of other plots with a fertilizer containing only nitrogen at a rate about 40 times lower than the normal one for N. The total carotenes (provitamin A) contents of the ripe lettuces were measured. Covering with a plastic sheet always decreased the total carotenes contents. The N+P+K+S fertilizer used at normal rate increased, relatively to the nitrogen fertilizer lacking of P+K+S and used at low rate, the total carotenes contents of the non-covered lettuces, but had no or low effect on the total carotenes contents of the covered lettuces.

The Effects of Selected Herbicide and Fungicide Treatments On the Carotenes and Xanthophylls in Lettuce

SummaryEarly and summer lettuces were grown in soils treated with one or both of the herbicides Kerb and C1PC; other lettuces were treated with one of the fungicides Benlate, Rovral or Ronilan, only one pesticide being applied per plot. In both the early and the summer lettuces the concentrations of the mixture of β-carotenes (provitamin A) were increased (relative to the untreated standard) by both the herbicides Kerb and CIPC applied either alone or together. Treatment with the fungicide Rovral caused the lettuces to contain higher concentrations of the mixture of β-carotenes; neither Benlate nor Ronilan changed the concentrations of the mixture of β-carotenes. Each of the pesticides had a similar effect on the concentration of the sum of the mixture of β-carotenes and the monohydroxy xanthophylls (the only xanthophylls which have a provitamin A activity) as it had on the concentration of the mixture of β-carotenes. The total xanthopohyll contents of the lettuces and the distribution of the monohydroxy-...

Unexpected Effects of Selected Fungicide Treatments On the Acid Content of Golden Delicious and Jonagold Apples

Abstract Several fungicide treatment schemes were assayed on ‘Golden Delicious’ and ‘Jonagold’ apples. The total content of free acids (measured by titration) and the contents of each of the main free acids (malic, citric, fumaric, syringic) plus their salts (measured by gas liquid chromatography of the silylated samples) in the freshly harvested apples were measured and compared to those obtained with the corresponding untreated apples (control). The fungicide treatments generally decreased the content of each of the free acids plus their salts, and of the total of free acids in the ‘Golden Delicious’ apples; the same fungicide treatments had no effect, or slightly increased the concentration of each of the free acids plus their salts and of the total of free acids, in the ‘Jonagold’ apples. However, the contents of citric acid plus its salts were generally increased by the fungicide treatments in both ‘Golden Delicious’ and ‘Jonagold’ apples.