Thompson, A.E.
In September, 1953 a recessive, chlorophyll-deficient mutant occurred spontaneously in a population of seedling plants of the variety Stokesdale. The mutant tentatively has been named albescent (ab). The cotyledons usually appear to be paler green than normal and very infrequently show some albino sectors. The first readily apparent expression of the gene is the presence of albino sectors in the first true leaf. Subsequent true leaves and the primary stem apex are usually devoid of chlorophyll reduced in size, thus giving a rosetted appearance. Some plants will produce lateral branches with varying degrees of albino sectoring. Portions of affected stems and leaves are usually white, but occasionally other parts may be pale yellow in color. Occasionally small green sectors develop erratically on leaves and stems, which appear to be completely albino. Flowers and fruits are likewise white or pale yellow until maturity. Skin color appears to develop normally during fruit maturation but carotenoid pigment production is severely limited in the fruits.
At the outset the mutant superficially indicated a possible virus infection. An inoculum was prepared from leaves of an albescent plant and normal tomato and pepper plants were inoculated. Five normal Stokesdale plants were successfully approach grafted to an albescent plant. In another instance a stem tip of a normal tomato plant was successfully cleft grafted to a branch of the albescent plant. In no instance did the albescent condition prove transferable.
The following table summarizes the genetic data obtained. No linkage data are available.
Summary of genetic data for the inheritance of the tomato mutant albescent (ab) from the variety Stokesdale.
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+/+ or +/ab ab/ab X^2 P
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+/+ X ab/ab (F1) 627 0 --- ---
ab/ab X +/+ (F1) 90 0 --- ---
ab/ab X (45 fruits) 0 189 --- ---
ab/ab X +/ab 4 1 3.2000 .05-.10
+/ab X ab/ab 66 61 0.1968 .50-.70
+/ab X +/+ 1117 0 --- ---
+/+ X +/ab 120 0 --- ---
+/ab X (F2) 3816 1248 0.3412 .50-.70
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Recent correspondence with Dr. C. M. Rick indicates similarity in nearly every
respect of this mutant and an independently derived one provisionally called
ghost (gh) he and coworkers are currently studying. Reciprocal crosses
between the two mutants are being made to test for allelism.