Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

Formation of tobacco mosaic virus in an animal cell culture

When a culture of diploid monkey kidney cells (B-SC-1 cells) was supplied with infectious RNA extracted from tobacco mosaic virus, the cells degenerated over a period of 23 days and particles similar to TMV in infectivity, sedimentation, morphology and serological properties, appeared in the supernatant fluid

Myooplasma-like bodies in french bean, dodder, and the leafhopper vector of the legume little leaf agent

Mycoplasma.like bodies were observed in the phloem sieve tube elements of French bean (Phaseolus vulgaris L.) and dodder (Guscuta australis R.Br.) carrying the legume little leaf disease agent. In dodder they occurred in small groups of approximately 5–30, in contrast to the very large numbers in bean. In bean, some of the bodies were located within the sieve plate pores

Observations on the relationship between mcoplasma-like bodies and host cells of legume little leaf-diseased plants

When seotions of the abnormal green petals and ovary of flowers from oowpea [Vigna BinenBiB (L.) Savi ex Haask] affeoted by legume little leaf disease, were examinedbyeleotron miorosoopy, numerous Mycoplasma-like bodies were observed in oertain sieve tube elements. Beoause of the looation of some of the bodies in sieve plate pores, it issuggested that they pass between sieve tube elements of the phloem via the sieve pores.Presumably this movement is involved in the systemio infeotion of the plant. Other observations indioated that at least at some stage of the infeotion, the bodies are present in intact oytoplasm, along with apparently normal organelles of the host cell. This observation contrasts with previously published eleotron miorographs of Mycoplama-like bodies in plants affeoted by yellows diseases. These miorographs have shown the bodies only in cells apparently undergoing cytoplasmio degeneration, or in cells oompletely devoid of oytoplasm. If the bodies are the aetiologioal agents of legume little leaf, the occurrenoe of them in intaot oytoplasm suggests a more highly speoialized host-parasite relationship than previous results have indioated

Measles virus

COOPER1 placed measles virus in the deoxyvirus group. There is now considerable evidence which is contrary to this view. The appearance of acridine-orange stained inclusions in measles virus infected cells under ultraviolet illumination suggests the presence of a ribovirus2. This is in agreement with the observations of Atherton3. Waterson et al.4 reported similarity of measles virus to myxoviruses, under the electron microscope. Waterson5 further showed that the three serologically related viruses, measles, canine distemper and rinderpest, are structurally identical with Newcastle disease virus (NDV), representative of a myxovirus sub-group. Further support for the similarity of measles virus and NDV is that these viruses undergo identical morphological changes during ether treatment, and the ability of measles virus to cause hæmagglutination

Adsorption of viruses on magnetic particles-II. Degradation of MS2 bacteriophage by adsorption to magnetite

The adsorption by magnetite of MS2 bacteriophage from 100 mg 1-1 NaCl solutions was studied using MS2 bacteriophage labelled with 32P in the RNA and 3H in the protein. After agitation for 20 min, the supernatant from suspensions of finely-divided magnetite and MS2 phage in 100 mg 1-1 NaCl, was assayed for remaining infective particles. Phage adsorption to magnetite was shown to occur over the range pH 4-7.5. At phH 6, 99.99% of the MS2 particles were removed from the supernatant and 32P and 3H were associated with the magnetite. When this magnetite was resuspended in 100 mg 1-1 NaCl at pH 10. 32P and 3H was released into the supernatant, although infectious MS2 particles could not be detected. Extracted, purified MS2 RNA labelled with 32P and MS2 protein labelled with 3H were used to study the adsorption and release of the virus components. Both the RNA and protein were bound at pH 6. When the pH was raised to 10, all 32P and 96% of the 3H was released into the supernatant. It is concluded that virus adsorbed to magnetite is disrupted at pH 10, and its components released into the medium. The free virus retains its infectivity at pH 10

The effect of ascorbic acid on infection of chick-embryo ciliated tracheal organ cultures by coronavirus

Chick embryo tracheal organ cultures showed increased resistance to infection by a coronavirus after exposure to ascorbate, while chick respiratory epithelium and allantois-on-shell preparations showed no increase in resistance to infection by an influenza virus or a paramyxovirus