Breeding for resistance to Heterodera in white clover

Summary White clover resistant to cyst nematodes was selected as a contribution to the study of the importance of cyst nematodes in the disappearance of white clover from grassland. Resistance was obtained from different sources viz from clones of the Foundation for Agricultural Plant Breeding selected for persistence, from New Zealand white clover, from the Swedish variety Kiwi and from the Italian variety Lodigiano. Inheritance was found to be most likely determined by more than one gene.The results of tests with three clover populations and seven Dutch sources of nematodes did not show clear differences in biotypes among the eelworms. Biotypes will not so easily appear as with organisms reproducing sexually because reproduction is practically only mitotic parthenogenetic.Resistance to cyst nematodes was not correlated with high glucoside contents.     

Partially carboxymethylated feather keratins. 1. Properties in aqueous systems

Feather keratins were extracted from chicken feathers with an aqueous solution of urea and 2-mercaptoethanol. The keratin solution obtained was dialyzed to remove the reagents. Upon dialysis, extensive protein aggregation occurred. To obtain stable solutions or dispersions in water, cysteine residues were modified prior to dialysis with iodoacetamide, iodoacetic acid, or bromosuccinic acid, thereby blocking free thiol groups and introducing hydrophilic groups. For the development of biodegradable materials with good mechanical properties from these biopolymers, disulfide bonds between the keratin molecules are needed. Therefore, cysteine residues were only partially modified by using different reagent/cysteine molar ratios. The reaction rate constants of iodoacetate with glutathione and 2-mercaptoethanol were successfully used to predict the degree of modification of keratin cysteine. It was shown that, for carboxymethylated keratin, fewer aggregates were formed for higher degrees of cysteine modification, while more protein was present as oligomers. Aggregates and oligomers were stabilized through intermolecular disulfide bonds.     

Production of tobacco mosaic virus in and its infectivity from leaves of two Nicotiana species treated with 6-azauracil

A correlation between the amount of virus as determined by infectivity test and that determined by a serological-spectrophotometric method was established in leaf discs ofNicotiana tabacum White Burley which had floated on a solution of 6-azauracil (AzU) before and after inoculation with tobacco mosaic virus. More virus, determined in the two different ways, was present in the AzU-than in the water-treated leaf discs at 24 and 48 h after inoculation. Thereafter, the amount of virus was less than that in the control. The inhibitory effect of the pyrimidine analogue on the amount of infectivity in sap from AzU-treated discs proved to be dependent on the dilution of sap used. The higher the dilution the more inhibition occurred.In inoculated leaf discs ofNicotiana glutinosa the formation of local lesions in the AzU-treated series was strongly inhibited at 48 h after inoculation whereas at that time the amount of virus determined by the serological-spectrophotometric method was higher than that in the water-treated control ones. The latter mentioned stimulating effect disappeared later than 48 h after inoculation and gave way to inhibition.The infectivity of tobacco mosaic virus from AzU-treated leaf discs of White Burley tobacco was 23% of that from water-treated controls when undiluted clarified sap was used.     

Serological and electron microscopical investigations of the relationship betweenSorgum red stripe virus and sugar cane mosaic virus

Summary Sorghum red stripe virus (S.R.S.V.) from Italy and sugar cane mosaic virus (S.C.M.V.) from Puerto Rico were investigated at Wageningen serologically and with the electron microscope.By means of the microprecipitation test (van Slogteren, 1955) a qualitative relationship was established between the two viruses (Table 1). Electron microscopical investigations showed that with regard to their length there was no difference between the two viruses (Fig. 1 and 2).Samenvatting Sorghum red stripe virus (S.R.S.V.), afkomstig uit Italië, en suikerrietmozaïekvirus (S.C.M.V.) uit Portorico zijn te Wageningen serologisch en elektronenmicroscopisch onderzocht. Met behulp van de microprecipitatietoets (van Slogteren, 1955) kon een kwalitatieve verwantschap tussen de beide virussen aangetoond worden (tabel 1). Elektronenmicroscopisch onderzoek wees uit, dat er wat betreft de lengte der virusdeeltjes geen verschil bestaat tussen de twee genoemde virussen (fig. 1 en 2).     

The occurrence of inclusion bodies in leaf epidermis cells of sandal affected with spike disease

Round or slightly oval inclusion bodies were found in low numbers in epidermal cells of spiked (expressing spike disease symptoms) leaves. They could not be demonstrated in epidermal tissue of apparently healthy leaves. The intracellular inclusions stained with phloxine and rose bengal. Their relationship to sandal spike virus is discussed.