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Title: Studies in root crops
Author: Davey, V. E. McM.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1930
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I. In the first season of growth the stem, or "neck" of the swede had undeveloped inter - nodes, but the intervals between leaf scars varied in different strains. II . Under certain environmental conditions, e.g. late frosts, the majority of plants in a variety developed longer stems. The response in some varieties was a general lengthening to 10 or 15 inches, in others it was hardly appreciable. III. In long- necked varieties, fully bolted and very short -necked plants were found in small proportions. These types when bred, were found to have had different hereditary tendencies. IV. Great modification in stem length was found in plants of a true -breeding swede 'bolter' strain. V. The "bulbless bolter" is a rogue found in swede crops. It was similar in appearance to winter swede -like rape, but was sometimes completely annual in life term. VI. Progenies of bulbless bolters were found to be very uniform and true breeding. VII. Hybrids obtained from swede x bulbless bolter were strongly developed annuals having partly developed ligneous bulbs, white flesh and lemon flowers. A purple - neck, white -fleshed hybrid, segregated 8.6 white to 1 yellow and 3 purple -neck to 1 bronze. The white flesh of the bulbless bolter was probably due to two pairs of dominant factors. VIII. Swede and bulbless bolter hybridised reciprocally when grown together. IX. The main anthocyanin colour difference on the superficial layers of the swede was found to be determined by either of two allelmorphs N₁ and N₂, the dominant character being detected by the uniform colouring of the internodes of the neck. X. Production of anthocyanin in the region of the shaw was found to depend mainly on the presence of two factors - (i) a purple-neck factor, and (2) a factor extending the area of pigmentation. XI. A number of modifications and minor variations in anthocyanin pigmentation were noted. XII. The two factors governing flesh colour were found to be unlinked. F₂ segregations of 15 white to 1 yellow-flesh were obtained. XIII. There was absence of linkage between flesh and neck colours. XIV. Variability in individual bulb weight was very great. It was subject to modification, but the influence of "total potential variability" of the strain was not proved. XV. Variability in individual dry-matter percentage was comparatively small. It was positively correlated with variability in bulb weight. The influence of "total potential variability" of the strain could not be proved. XVI. The inverse correlation between bulb weight and dry- matter percentage was found to be subject to considerable modification. It was not affected by the "total potential variability" of the strain. XVII. Increase in total solids percentages of bulbs were due to independant increments of both soluble and insoluble substances, the former being more strongly correlated with total solids percentage. XVIII. Hereditary variations were isolated by selection from commercial strains, but not from twice or thrice-selfed lines. XIX. Individual plants high in bulb weight and dry -matter percentage were found to have been modified in one or other of these characters. XX. When bulbs were sampled by boring cores, deflections from the true alignment caused certain excerimental errors which were estimated. The variability of horizontal and diagonal core results was similar. XXI. In the middle region of the bulb the bark was 32% richer in dry-matter than the flesh. The peripheral shell of flesh 1 cm. deep was 6% above average. There were no great differences between portions nearer the centre in the equatorial plane, though those from the South side were slightly richer than those from corresponding positions on the North. XXII. Cores containing the vascular tissues feeding side roots were not significantly different in dry- matter percentage from other cores in the same transverse plane. XXIII. Diagonal cores were slightly higher in dry- matter percentage than horizontal cores. Both types of core gave lower values than the whole bulb.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available