2. White-capped red pericarp. - In last year's News Letter I presented data which I interpreted as showing that white-capped red pericarp of such varieties of maize as Bloody Butcher is not allelic to ordinary red pericarp, P, as had been supposed, but is conditioned by multiple genes at least one of which is linked with red cob color and therefore with P. I presented data from F2, F3, and backcrosses of the cross of colorless pericarp and white cob, W-W, with white-capped pericarp and red cob, C-R. From this cross, the four possible combinations of pericarp and cob colors were obtained, namely, C-R, C-W, W-R, W-W. Grades of pericarp color from 0, no color, to 6, the color intensity of the Bloody Butcher parent, were reported and the behavior in inheritance was shown to be that typical of quantitative characters.
This year I present data from further F3 cultures and also from F4 cultures. For brevity in the accompanying table, I have grouped together cultures which have about the same ranges of variation, and may, therefore, in so doing, have combined genetically heterogeneous material.
Certain conclusions may be drawn from these data: (1) - From the cross W-W × C-R, there have appeared in F3 or F4 in relatively true breeding form, the four possible combinations of pericarp and cob colors, namely, W-W (item 1), W-R (item 2), C-W (items 21, 28), and C-R (items 20, 25, 29, 30, 33). (2) - There have appeared types that breed relatively true for pericarp color while still segregating for cob color: W-R and W-W (item 3). C-R and C-W (items 22, 26, 27). (3) - Some cultures still show marked variation in intensity of pericarp color while breeding true for red cobs (items 11, 17) or white cobs (items 10, 16). (4) - In all cultures that have any pericarp color and that are segregating for cob color, the ears with red cobs have a higher mean grade of pericarp color than do those with white cobs. (5) - In a few cases, the ears with white cobs have no pericarp color while some or all of those with red cobs have more or less pericarp color (items 5, 6, 7, 18). (6) The gene or genes conditioning pericarp color in these instances (5 and 6 above) may be assumed to be in chromosome 1 near the locus of P. (7) - Selection is effective in establishing lines with diverse intensities of pericarp color.
From the trisomic cultures of Mr. Einset has come the suggestion that one or more genes affecting white-capped red pericarp color may be in chromosome 5. In a culture segregating for trisome 5 and for this type of pericarp color, the ears of trisomic plants had unmistakably more intense pericarp color than did those of disomic ones. This behavior is to be expected of characters that show a gene-dosage effect as white-capped pericarp color does, A beginning has been made in the use of the other trisomes in an attempt at a further genetic analysis of this pericarp color.