4. Relation between size and position of self‑colored (mutant) stripes and heritability in variegated pericarp corn.

An ear of corn either homozygous for VV or heterozygous for VV and a colorless P allele will show a wide range of expression of striping among its component kernels. The range may include kernels with the entire pericarp colorless, kernels showing a few to a great many very fine stripes, kernels with one or more wide striped in addition to the fine ones, and kernels which are entirely self‑red.

Variegated kernels with one wide stripe of self‑red pericarp color were selected from VV/WR ears. These kernels were a sample of VV from a variety of sources. Comparable numbers of kernels showing only finely striped variegation were taken from the ears. The few entirely selfed kernels on the ears were placed in a third category. Stripe width and position were recorded in units which represented 10 degree of arc, assuming that the crown of the kernel could be treated as a deformed circle. The zero point on the scale corresponded to the silk attachment which lies directly above the midline of the embryo. Successive 10 degree increments were marked on large scale models of variously shaped kernels with the numbering progressing in the counter‑clockwise direction. Each parent kernel, with a wide red stripe (covering 10 degree or more of arc) was scored against one of the models.

Kernels on which the stripe covered all or part of the enbryo were subdivided into seven classes. Kernels on which the stripe was abgerminal were also divided into seven classes, such that any one class could be compared with the one diametrically opposite it on the embryo side. Two classes with the stripe restricted to the sides of the kernels were also selected.

The results are based upon 527 ears raised in 1949 and 1140 ears raised in 1950. Each kernel with a self‑red stripe was planted and individually staked. The resulting plant was scored for pericarp color (red RR/WR, variegated VV/WR, or colorless WR/WR). Within sampling limits, one‑half of the ears in each group were colorless, as expected. Three groups, each comprising seven classes, were available for comparison. Group I kernels had a stripe covering all or part of the embryo, and in addition the stripe included all or part of the comparable 60 degree arc on the abgerminal face. Group II kernels had a stripe covering all or part of the embryo, but the stripe did not extend over the comparable 60 degree arc on the abgerminal face. Group III kernels had a stripe which covered all or part of the 60 degree abgerminal arc but did not extend over the embryo.

The results are summarized in tables 3 and 4. The finely striped variegated kernels, which may be considered the control for this experiment, gave 4.9% red ears. All classifications of kernels with wide self‑red stripes showed percentages of red ears in excess of this. Kernels with the stripe confined to the side of the kernel showed an appropriate two‑fold increase, and kernels which were entirely self‑red produced only red‑eared progeny. The probability of obtaining a red‑eared plant from a variegated kernel with a self‑red stripe 10 or more degrees of arc in width is significantly higher if the stripe covers all or part of the embryo (Groups I and II), rather than a corresponding area on the abgerminal face (Group III). The probability of obtaining a self‑red ear is also significantly higher in a class in Group I than in the corresponding class in Group II.

Table 3

Distribution of progeny from groups of kernels (VV/WR) of differing
variegation pattern (1950 data).

	Group	Number of Progeny			Per cent red^1
		Red	Variegated	Colorless
I	Stripe on embryo, also on back	84	32	112	72.4
II	Stripe on embryo, not on back	77	138	233	35.8
III	Stripe on back, not on embryo	24	111	140	17.8
IV	Stripe on side only	8	79	100	9.2
V	Finely striped variegation	35	677	760	4.9
VI	Entirely self red	23	0	26	100.0

¹ Based on variegated and red ears.

Table 4

Percentage of red progeny in sections within Groups I, II, and III
(1950 data)

Stripe position	Percent red^1
	Group I	Group II	Group III
Covering more than half of embryo or corresponding area on back	93.0	66.1	26.9
Covering half of embryo or corresponding area on back	70.7	28.4	19.5
Covering less than half of embryo or corresponding area on back	47.0	19.0	3.1

¹ Based on variegated and red ears.

Ronald E. Anderson