excessive flower number, poor fruit set, and rough fruit. In developing the parental j-2 cultivar, the adverse effects
were evidently prevented not by crossing-over but rather by an independent modifying factor epistatic to the
undesirable pleiotropic effects of the j-2 gene.
One such modifying gene is o. Segregants from o X j-2 crosses that were recessive for both of these genes
all had a good set of smooth fruit, and they did not have the large stem scar and radial cracking that was associated
with all the j-2 o+ plants, including the few with otherwise good fruit type. Other genes also modify the adverse
effects of the j-2 gene, since breeders have developed j-2 o+ cultivars, such as MH-1, with good fruit set and type.
Schiavi, M., B. Campion, and G. P. Soressi. Allelism test between torosa2 and blind mutants.
The mutant torosa2 (to2) described by Stubbe (TGC 17:10) proves to be particularly interesting for breeding
tomato varieties suitable to high density population and mechanical harvesting (see Campion TGC 30).
Phenotypically torosa2 appears quite similar to blind (bl) (TGC 9:9). Both the mutants, in fact, show very few lateral
shoots, 1-3 fruits per truss and often stop growth after the first or second inflorescence; a peculiar feature is the high
frequency of flower and fruit fasciation.
To test their possible allelism, torosa2 (cv. Lucullus) was crossed with 3 different stocks of blind: 1 from Rick
and 2 from Darby. The F3 progenies examined, however, were restricted to those originated by the F2 family from
the cross with the blind source from Rick. The results obtained are given in tables 1-4. All the F1 plants were sp+ and
exhibited 1-6 lateral shoots. In the F2 progenies there were phenotypes without lateral shoots, with 1-6 lateral
shoots, and undistinguishable from normal.
The analysis of each F3 family from individual F2 plants evidenced the appearance of like normal phenotypes
from blind, non-blind, and apparently normal F2 plants. These results strengthen the hypothesis that the two mutants
are allelic to the same bl locus but each of them possesses at least 1 modifer gene, whose action determines a wide
variability ranging from blind to apparently normal phenotypes.
The expression of the bl gene as far as the number of lateral shoots, the cessation of growth, and the flower
and fruit fasciation are concerned, is, besides, influenced by other genes (sp, d, etc.) and by environmental
conditions (temperature, nutrition and light).
Such indications point out the importance of the cross material and selection when torosa2 or the blind
mutant is utilized for breeding purposes.
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