High-yielding Strains Research Articles

Genetic segregation in a high-yielding streptomycin-producing strain of Streptomyces griseus.

The streptomycin-producing Streptomyces griseus HP spontaneously segregated non-reverting derivatives with altered phenotypes. Clones characterized by increased spore formation and decreased streptomycin production were found. Two other types of derivatives were defective in aerial mycelium and streptomycin formation as well, but differed in the capacity to synthesize a yellow pigment. These derivatives were examined with respect to further properties. The stability of S. griseus HP was investigated in relation to conditions of continuous culture. Both at 26 and 30 degrees C, under glycerol and NH4Cl limitation a rapid segregation and enrichment of streptomycin-non-producing derivatives occurred. At 34 degrees C and glycerol limitation segregation began only after about 35 generations of continuous culture. In NH4Cl-limited chemostats the original strain was stable during 80 generations. In the course of the continuous culture experiments it was shown that the onset of genetic segregation within mycelia can be detected before it becomes obvious in colonies grown from the mycelia. This was achieved by fractionation of the mycelia by protoplast formation and subsequent plating on regeneration medium allowing colony growth and differentiation.

Fresh approaches to antibiotic production.

New antibiotics are needed, (a) to control diseases that are refractory to existing ones either because of intrinsic or acquired drug resistance of the pathogen or because inhibition of the disease is difficult, at present, without damaging the host (fungal and viral diseases, and tumours), (b) for the control of plant pathogens and of invertebrates such as helminths, insects, etc., and (c) for growth promotion in intensive farming. Numerous new antibiotics are still being obtained from wild microbes, especially actinomycetes. Chemical modification of existing compounds has also had notable success. Here we explore the uses, actual and potential, of genetics to generate new antibiotics and to satisfy the ever-present need to increase yield. Yield improvement has depended in the past on mutation and selection, combined with optimization of fermentation conditions. Progress would be greatly accelerated by screening random recombinants between divergent high-yielding strains. Strain improvement may also be possible by the introduction of extra copies of genes of which the products are rate-limiting, or of genes conferring beneficial growth characteristics. Although new antibiotics can be generated by mutation, either through disturbing known biosyntheses or by activating 'silent' genes, we see more promise in interspecific recombination between strains producing different secondary metabolities, generating producers of 'hybrid' antibiotics. As with proposals for yield improvement, there are two major strategies for obtaining interesting recombinants of this kind: random recombination between appropriate strains, or the deliberate movement of particular biosynthetic abilities between strains. The development of protoplast technology in actinomycetes, fungi and bacilli has been instrumental in bringing these idealized strategies to the horizon. Protoplasts of the same or different species can be induced to fuse by polyethylene glycol. At least in intraspecific fusion of streptomyces, random and high frequency recombination follows. Protoplasts can also be used as recipients for isolated DNA, again in the presence of polyethylene glycol, so that the deliberate introduction of particular genes into production strains can be realistically envisaged. Various kinds of DNA cloning vectors are being developed to this end. Gene cloning techniques also offer rich possibilities for the analysis of the genetic control of antibiotic biosynthesis, knowledge of which is, at present, minimal. The information that should soon accrue can be expected to have profound effects on the application of genetics to industrial microbiology.

Gene composition of high-yielding influenza vaccine strains obtained by recombination.

The genetic composition of 11 high-yielding recombinants of influenza virus was determined by polyacrylamide gel electrophoresis of the 32P-labeled RNAs obtained from the recombinants and their parental viruses. The high-yield recombinants that were selected for potential use as vaccine strains contained the surface hemagglutinin and neuraminidase antigens of the low-yielding parental viruses. The increased growth capacity of the recombinants is associated with the presence of genes derived from the high-yielding laboratory strain A/Puerto Rico/8/34. Although increased growth capacity in these recombinants could not be attributed to specific genes or gene combinations, all of the high-yielding recombinants examined derived the M gene from the A/Puerto Rico/8/34 parent.

Maize protection in Zambia

A major preoccupation of agricultural policy makers in the 1970s has been how to obtain maximum benefit from new high-yielding seeds. ‘Tailored packages’ have been developed to suit conditions in different countries, specialized training has been arranged for farmers to help them cope with the techniques needed for the new seeds, and banks, at least in some countries, have extended their activities deeper into the rural areas. Some attempts have also been made to avoid the ‘freezing out’ of small farmers for whom the new seeds, with their demands for precise applications of water and fertilizers, were likely to be a risky business. The emphasis has been on increased output. Less effort has gone into programmes designed to deal with a problem that the high-yielding strains create once they have been grown and harvested — an increase in post-harvest losses. Estimates suggest that between 20% and 40% of the grain produced in developing countries each year ends up nourishing insects, rodents and birds or is otherwise spoiled by fungi. The food lost in Africa alone each year could feed 55 million people. India loses sufficient grain to feed 50 million people a year. The high-yielding varieties of seeds are even more susceptible to loss than traditional seeds because they cannot be kept securely in traditional storage facilities. A good example of this problem — as well as an innovation which is attracting attention from many other countries — is in Zambia where maize is the staple crop.

Regeneration von intakten Pflanzen aus diploiden und haploiden Kalluszellen von Catharanthus roseus

Summary Intact plants of Catharanthus roseus have been differentiated from haploid and diploid calluses. These regenerations have been initiated by cultivating the tissues 13 months (diploid cells), respectively 5 months (haploid cells) with different combinations concerning the concentrations of phytohormones (kinetin and β-indolyl-acetic acid). Since four years we have grown the induced plants in the greenhouse and have propagated them by shoots and seeds. Phytochemical investigations have shown that the regenerated plants may contain twice as much serpentine/raubasine as the stock plants and several times as much of these alkaloids as the calluses the regenerates came from. The importance of tissue cultures for production of high-yielding strains of medicinal plants has been stressed especially.

Ragi Co 11 An Early Maturing High Yielding Strain

Ragi EC. 4849. a brown grained selection from an Andhra Pradesh variety developed by pureline breeding was evaluated for yield and other economic attributes over several locations in the State of Tamil Nadu from 1971 to 1977. The selection matured in 90-95 days and found to be superior in grain yield to the high yielding ruling strain Co. 10 by 10 per cent in the rosearch centres and 15 per cent in the cultivators fields. In All India trials also the selection proved its superiority. It possessed saline tolerance and contained a higher percentage of protein (10,86). The Oragi selection has thus, been released as a new high yielding strain Co 11 for general cultivation in the Tamil Nadu State.

Co. 1 Brinjal A High Yielding Strain.

Intensive selection work carried out at the vegetable unit of the Faculty of Horti- culture, Tamil Nadu Agricultural University, Coimbatore resulted in the release of a new strain. CO. 1 brinjal suited to Tamil Nadu. It yields on an average 24 t/ha of fruits with 41.5 per cent increase over local. It offers good scope for cultivation in Tamil Nadu due to its high yield, resistance to nematodes. low seed content and good keep- ing quality.

Improvement in amyloglucosidase production following genetic recombination of Aspergillus niger strains

Recombination has been demonstrated in amyloglucosidase-producing strains of Aspergillus niger. A high-yielding strain has been crossed, parasexually, with a low-yielding strain from the same genealogy. Recombinants have been produced, having the efficient broth filtration characteristics of the low-yielding strain. One such segregant was superior, for the industrial production of amyloglucosidase, to the best parent strain previously used for that purpose.

Morphophysiological determinants of yield in rapeseed (Brassica campestris and Brassica napus). I. Growth and morphological characters

Variation in sowing date was found to have a marked effect on the seed yield and different morphological and growth characteristics of spring cultivars of the oilseed rape species Brassica campestris and Brassica napus. The two species differed appreciably, however, in their responses to successive delays in sowing date. In B. napus, there was a significant and continuous decline in seed yield with later sowings. This decline in seed yield was associated primarily with a reduction in the total dry weight of the plant at the final harvest which, in turn, was most closely correlated with the duration of the vegetative phase of growth. The total dry weight of the plant and the seed yield were greatest in the first sowing where flowering was substantially later than in either of the later sowings. Since earlier-flowering cultivars of B. napus would be better adapted to Western Australian conditions, where there is a rapid decline in soil moisture reserves during the spring, significant improvements in seed yield could depend largely on increasing the rate of pre-anthesis growth. In this experiment, however, no significant variation in the relative rate of growth prior to flowering was observed because of the marked negative association between net assimilation rate and leaf area ratio. Further studies of the variation in growth amongst a far wider range of genotypes will, nevertheless, be necessary to properly assess the feasibility of increasing relative growth rates by selection. The seed yield of B. campestris was substantially greater in the second sowing than in either the first or third sowings. Although seed yield was significantly correlated with both total dry weight of the plant at final harvest and the harvest index, the latter appeared to be the most important determinant of seed yield in this species. By contrast with B. napus, most of the dry weight of the plant at the final harvest was accumulated during the post-anthesis phase of growth. Accordingly, the character leaf area duration between anthesis and final harvest was found to be the most significant determinant of the total dry weight of the plant in B. campestris. The leaf weight ratio of the plant at anthesis also contributed significantly to total dry weight at the final harvest; this indicates that the pattern of dry matter distribution in the plant during the vegetative phase could prove a useful criterion for selecting potentially high-yielding strains of this species.

Biosynthesis of ergotamine by Claviceps purpurea (Fr.) Tul.

High-yielding strains of Claviceps purpurea (Fr.) Tul, grown on a defined medium, have been used for a study of the biosynthesis of the peptide ergot alkaloid, ergotamine. l-[U-(14)C]tryptophan, dl-[2-(14)C]mevalonic acid lactone, sodium [2-(14)C]acetate, sodium [(14)C]formate and the methyl group of l-[methyl-(14)C]methionine were efficiently incorporated into the peptide alkaloids and specifically labelled the ergoline moiety of ergotamine. These results are the same as previously found for the biosynthesis of other ergot alkaloids. Time-course incubation experiments demonstrated that l-[U-(14)C]phenylalanine, l-[U-(14)C]proline and l-[U-(14)C]alanine were incorporated into the peptide ergot alkaloids. Chemical degradation of the radioactive alkaloid derived from additional precursor incubation experiments showed that phenylalanine and proline function as the most efficient precursors, and specifically label the constitutive side-chain phenylalanyl and prolyl moieties of the alkaloid. The evidence obtained from l-[U-(14)C]alanine-incorporation experiments was inconclusive. However, degradation of ergotamine isolated after incubation with dl-[1-(14)C]alanine, showed that the carboxyl group of the labelled amino acid was specifically incorporated into the alpha-hydroxy-alpha-amino acid residue of the alkaloid. This, in conjunction with the l-[U-(14)C]alanine-incorporation results, showed conclusively that all three carbon atoms of alanine were incorporated as a biosynthetic unit into the alpha-hydroxy-alpha-amino acid moiety of ergotamine.

Genetic Variability in the Mungbean, Vigna radiata (L.) Wilczek

Three hundred and twenty‐one strains of mungbeans, [Vignu radiata (L.) Wilczek] originating from 18 American, Asian, African, and Middle Eastern countries were grown at Columbia, Mo. and evaluated for yield, days to first ripe pod, plant height, length of first branch, pods per plant, number seeds per pod, 1000 seed weight, virus resistance, mildew resistance, percent protein, percent lysine, and percent methionine. A wide range in genetic variability was identified for each character examined. Performance of the 32 (10%,) highest‐yielding strains is compared with the performance of the total population of 321 strains. Relative to the total population, the high‐yielding strains tended to be moderately early, to have moderately large‐size plants as measured by height and length of the first branch, to have a large number of seeds per pod and moderately high seed weight, and to be resistant to virus. Protein, lysine, and methionine content varied widely among the high‐yielding strains. No single strain excelled in the three yield components — pod number, seeds per pod, and seed weight — or in the three nutritional components — protein, lysine, and methionine.

Related studies of a recombinant influenza-virus vaccine. I. Derivation and characterization of virus and vaccine.

Genetic recombination of low egg-passage, low-yielding, heat-inactivated HK/ Aichi/68 influenza virus and a standard, high-yielding laboratory-adapted strain (A07PR8734) resulted in the isolation of a recombinant (X-31) antigenically indistinguishable from the Aichi virus but with hemagglutinin-yielding capacity in the chick embryo comparable to that of PR8 (i.e., 16to 32-fold greater than Aichi). Other nonantigenic markers inherited by X-31 from PR8 include spherical morphology and virulence for the lungs of mice. A pilot commercial production lot of X-31 inactivated vaccine was administered to 16 human subjects of various ages; 8796 responded significantly as measured by at least one of nine different serologic tests. These results demonstrate the feasibility of using genetic recombination for the deliberate design of vaccine viruses with the desired optimal characteristics.

Influence of Different Levels and Combinations of N, P and K on the Yield of Grain and Straw in Certain High-yielding Paddy Strains

A number of high fertility strains of paddy have been recently introduced and their fertiliser requirements are very high. But the optimum requirements of fertilisers for these varieties are not yet clearly known. Fertiliser recommendations are made at present somewhat empiri- cally, due to lack of knowledge about the optimum dosages for these varieties. A clear idea of the specific fertiliser requirements for these varieties will greatly reduce the possible wastage of applied fertiliser, on one hand, and also bring about the full expression of the genetic potential of these varieties with reference to response to applied fertilisers. Hence the present study was planned and carried out with a view to furnish information on this aspect which is very urgently needed today, especially in the context of economising fertiliser use. With these objectives in mind a pot culture experiment was laid out on the soil from wetlands of Central Farm, Agricultural College, Coimbatore, with the paddy strains I.R. 8, Taichung (Native) 1, and CO. 32.

The power of active individuals

We read that India has harvested 95 million tons of wheat this summer, 6 million tons more than the previous best harvest. Much credit is given to the U.S. foreign-aid program in which farm experts from the U.S. introduced high-yielding strains of wheat, helped build fertilizer plants, and overcame some of the natural suspicion and doubts of the people of the country by getting some of them to take part. This is not the first time that grain production has been increased significantly by the introduction of scientifically based methods and technological improvements. It was done with corn in Mexico under the leadership of the Rockefeller Foundation and that spirit has been carried into some of the rice-growing regions of the Philippines and other areas of the Orient. While such achievements are not a sign we have overcome broad problems of feeding the world's people, they allow certain spare comfort to be taken from what ...

Identification of a compound related to 6-aminopenicillanic acid, isolated from culture media of Penicillium chrysogenum.

IT has previously been reported1 that when a high-yielding strain of Penicillium chrysogenum was grown in shake flasks in a chemically defined arginine–lactose medium2 containing sodium sulphate labelled with sodium-35 in the absence of phenylacetic acid, a radioactive compound extractable with n-butyl-acetate was formed instead of benzylpenicillin. This compound differed in its chromatographic properties from any of the known penicillin degradation products.

Radioactive isotopes in the study of synthesis processes in yeast organisms

A study was conducted to determine the effect of various low cost organic wastes as flavinogenic factors and the various concentrations at which they induced flavinogenecity resulting in higher yields of riboflavin. A high-yielding riboflavin strain; Eremothecium ashbyii NRRL 1363 was chosen to determine the flavinogenicity. Carbon source at 50gl−1 (dextrose equivalents) of molasses and nitrogen source at 50gl−1 (weight/volume) of peanut seed cake were found to be optimal levels to yield higher riboflavin. Among the organic wastes, (beef extract, hog casings, blood meal, fish meal) hog casings in association with fish meal supported the highest yield of riboflavin. Among the different recovery processes studied, a vacuum drying process was the most efficient allowing maximum yield, followed by drying at 90 °C and freeze-drying. It is apparent from this study that inexpensive or waste organic materials could induce E. ashbyii to synthesize and secrete riboflavin at higher levels in the medium and this could be purified using a vacuum drying process. This bioconversion process allows us to recycle the biomaterials and produce a value-added product of economic importance.

Penicillin production by high-yielding strains of Penicillium chrysogenum.

Penicillin production by high-yielding strains of Penicillium chrysogenum.

Penicillin Production by High-yielding Strains of Penicillium chrysogenum1

Penicillin Production by High-yielding Strains of Penicillium chrysogenum1

Vernalization of Rice

IN certain parts of Bengal considerable rice crop of â ausâ paddy* is damaged, due to the incidence of early flood (July and August) submerging the whole crop when it is about to ripen. So it was considered that â ausâ plants might be made to escape the flood by reducing their life-period by the technique of vernalization. It must be mentioned that among the numerous varieties of â ausâ paddy there is no variety the life-period of which is less than ninety days, and these are usually low yielding. Hence an approach to the problem was made by reducing the life-period to less than ninety days of the existing high-yielding strains by vernalization.

THE BIONOMICS OF THREE SHORT-DURATION VARIETIES OF RICE

In the evolution of high-yielding strains of s variety, a study of the latter to find out its response under varied con ditions of farming is of the utmost importance. Unless its behaviour is previously known the selection will have to be based only on the empirical methods of selecting well tillered and long eared plants. Popular requirements may vote for an attractive ear while tillering may carry weight with considered judgment. But this cannot be said to hold true as a general principle in all varieties of the same duration and much less in those of different durations. The nature, number and mode of tillering though partly a genetic manifestation are a function of the life-period. It has always been the experience in cereals that to make a selection for high yield is no easy task, though many useful characters are correlated.