Brauer, O. and C. M. Rick.
The name ghost and the symbol gh have been applied to a recessive mutant that appeared in a culture of determinate San Marzano type bred by Mr. G. C. Hanna. Ghost seedling appeared in about 1/4 of the selfed progeny of a single normal plant of this line. Since nothing of the same phenotype has appeared in the parental lines or other derivatives, we conclude that gh is the product of spontaneous mutation.
Ghost phenotypes germinate and emerge from the soil no normally. Hypocotyls appear normal except for shorter trichomes. Cotyledons are allways green, but have irregular blotches of paler green color that usually permit identification of gh before true leaves appear. The amount of sabsequently developed green tissue is variable: the first true leaf may be entirely green or entirely white, but usually has a basal green area of varying size; most of the second leaves are entirely deficient and a rapid trend toward absence of chlorophyll is associated with further growth. Once deficiency is complete it remains so, except for occasional, sporadic, small areas of green tissue. Chlorophyll rarely persists to the level of inflorescences and appears infrequently as longitudinal streaks on the unripe fruits.
Most of the deficient areas are entirely white, but occasional plants attain a constant pale yellow color. Anthocyanin appears to be normal and is very conspicuous in the absence of chlorophyll. Deficient leaves are greatly reduced in size and have more acute segments. Hairs appear to be numerous but presumably only as a result of the concentration caused by reduced size of leaves and internodes.
The grafting of normal scions on gh stocks induces a greater development of green tissue in shoots emerging from the gh stock. The reason for this is not clear, but may be vested in the fact that these shoots emerged adventitiously from the hypocotyl. Such grafted ts and rare ungrafted seedlings with unusually large amunts of chlorophyll can flower and set fruit. Flowers are subnorml in size; fail to open. Pollen is variable, often highly aborted, but fruits with seed my develop after self-pollination. Externally and internally these fruits exhibit a milky white color at all stages except at maturity, when the epidermis suddenly develops the normal yellow pigment, and a similar yellow color appears in the gelatinous material surrounding the seeds. The green stripe seen an a few fruits turned at maturity to a red color, which dissection revealed to be present only in the flesh. The fruit pigments have been extensively analyzed by Dr. G. Mackinney, who has found that the skin pigment is the normal alkalli-soluble flavonoid, and that colored carotenoids are absent or at very low levels and colorless carotenoids at unusually high levels in the ripe fruits.
Seeds obtained from selfing gh plants germinate and yield only gh seedlings. All F1 gh x + and reciprocal have + phenotype. Recovery of gh segregating progenies is good the F2 fit usually being close. All data indicate normal transmission of gh through pollen and ovules and no influence of cytoplasmic factors.
The following F2 data vere obtained in an attempt to locate gh:
Combination Contingency
+ + + tester gh + gh tester X^2
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gh - al 328 113 93 32
ga - H 265 176 67 58
gh - rv 381 60 121 4 10.4**
h - a 311 141 154 8 205.3**
gh - a 427 176 150 11 46.5**
gh - c 463 125 140 36
gh - d 327 125 127 35
gh - l 362 90 108 54
Later tests indicated indipendence of gh and rv, the earlier association
having results from misclassification. Following this lead of linkage between
gh and a, we made a cross between the gh stock and Butler's a-hl tester,
yielding the following F2:
First sowing Total % crossingover a - hl (C) 919 95 103 242 1359 16 +- 0.7 gh - hl (R) 691 336 331 1 1359 5.5 +- 1.8 gh - a (R) 701 326 313 19 1359 24 +- 1.7 Second sowing a - hl (C) 1804 290 227 492 2813 19.5 +- 0.5 gh - hl (R) 1367 781 664 1 2813 3.5 +- 1.2 gh - a (R) 1467 681 627 38 2813 24 +- 1.1The proportion of hl is significantly high in the second sowing, otherwise single gene segregations are good. The a-hl-gh order suggested by these data is further borne out, by the fact that both gh-hl crossovers were a-hl-gh. The following approximate location on V is therefore indicated: a - 19 - hl - 5 - gh.