Henderson, W. R. and W. N. Brown
This mutant was found in a planting of Purdue F2. Both reproductive and vegetative parts are affected in several ways. The most obvious change in the flower occurs in the androecium, where variation exists in expression, but not so great as to cause difficulty in identification. The variation in expression ranges from stamenless, through petaloid stamens, to an occasional flower with one or two functional stamens. However, the predominant flower type is intermediate, with petaloid stamens adnate to the pistil. The sepals in all mutant flowers are broad and more blunt than normal. The gynoecium is also defective, with only a few seeds being produced when mutant flowers are pollinated with pollen from fruitful plants. The latter defect, in part, is attributed to a reduction in the adhesive quality of the stigmatic surface.
In addition to the above effects of the mutant gene, leaf form is also aiffected. The leaflets are obovate in shape, margins nearly entire, and the apex distinctly blunt, therefore, the symbol bn (blunt) is proposed. This description pertains especially to the terminal leaflet. Identification can be accomplished accurately when the fourth true leaf has expanded, but not prior to this stage.
These two mutant characteristics are attributed to a single recessive gene. No recombinants were observed in 2093 plants during two seasons testing, using different genetic background material. The Chi Square value for the F2 population is 0.48, for the backcross population of 150 plants, 2.16. Again no recombinants were found.
When Red Jacket, used as the male parent, was crossed with the mutant, segregates containing the double homozygous recessive genes, bn and c, produced leaves similar in shape to potato leaf, but lacked the basal lobes, and were conspicuously blunt, more closely resembling bn. Independent assortment between bn and c, and bn and u was also indicated.
No difficulty arose in identifying either the mutant flower or leaf type.
A distinct delay in flowering associated with bn plants was evident.
From one to two weeks elapsed from the time the first flower reached anthesis in cluster one of be plants, until those of bn reached the same stage of development.
The following characteristics were generally associated with bn segregates, but sufficient variation within plants and between plants casts doubt upon a definite relationship with bl, but perhaps they are worthy, nevertheless, of note. These were: leafy and running flower trusses, an increase in the number of flowers per cluster, and self-pruning habit producing a somewhat upright, bushy habit of growth.
Gene bn appears to add to the growing list of genes with pleiotropic effect.