Persson, A. R.
For some time I have been engaged in a study of induced chlorophyll mutants in tomato. This work has had several aims and aspects. We have especially been interested in using this work in order to get an understanding of the genetical system controlling the chlorophyll apparatus in tomato and to get a model of one type quantitative inheritance. The greater part of this work was done while I was on a National Academy of Sciences grant at the University of California, Davis, California. A special thank I express to Dr. Charles Rick who gave me very valuable help throughout the vork.
Most of this study has been done with an aurea mutant. This particular mutant was probably induced by X-ray treatment (after presoaking for 24 hours, the seed was treated with 10 000 r). The mutant was discovered in X1 due to its appearance. A branch of the plant had variegated foliage withlaurea and white patches although the greater part of the leaves was green. In X2 there also occurred a small chlorine plant which was named extreme miniature, min^ex. This may be the smallest, viable mutant known in tomato. It apparently arose simultaneously with the aurea type but segregates independently. This chlorine mutant may have as many as ten internodes on a 3" high stem. It does not set normal flowers, but by grafting on a normal plant it grows, flowers and sets fruit, but the main growth habit of the mutant is maintained. Apparently the mutant is lacking some fundamental growth principle.
The major part of the study has been in connection with the induced aurea type which here is given the general term A/+, but it is probably identical with the known Xa/+. In contrast to the Xa/+ type described by Butler & Chang (Can. J. Botany, 36,(1958), the 1:2:1 ratio is as a rule realized.
The yielding ability of the A/+ plants is tested under various environmental conditions. In most cases, they have yielded less than +/+ plants. In one experiment, under favorable growing conditions, the yield was about the same for both types. The reason for the apparent discrepancies among the results of different yield tests appears due to be the specific reaction norm of the A/+ plant towards the environment. Noteworthy is the fact that A/+ plants utilize a longer day much better than +/+ plants. On the other hand, high light intensities seem to be detrimental to the A/+ types. Its chlorophyll suffers a photodestruction. This was also shown by the work of Butler & Chang.
In growth experiments the dry matter ratio of +/+ to A/+ is compared at certain stages of growth, but changes with the age and the size of the plants, The chemical composition of the leaves and the fruits of the A/+ type is compared with the +/+ type. Both the foliage and the fruits of the A/+ type contain somewhat more proteins and minerals than the +/+ type.
The dosage effect of the A gene is studied in diploid and tetraploid material and also in trisomies and in a single triploid. The dosage effect is geometric rather than arithmetic, but the reduction in chlorophyll does not follow a constant factor. The dosage effect is greatly influenced by temperature and daylength.
The stability of the A gene is studied in reirradiated material, and from this it has been possible to extract several distinct variegated types.
In connection with physiological work on gibberellic acid it was demonstrated that the A/+ plants are influenced more strongly by gibberellin than +/+ plants.