Pt (Polytypic ear) is a dominant gene on chromosome 6 in maize which causes a variety of disturbances in floral development (see Nelson and Postlethwait, Amer. J. Bot. 41:734-748, 1954, and 51:238-243, 1964). Among biochemical correlates of Pt expression is elevation of anthranilic acid level in developing florets (Williams, Dissertation Abstracts 27:3801B, 1967).
Homozygous Bf (Blue fluorescent) maize seedlings and heterozygous/homozygous Bf anthers accumulate sufficient amounts of anthranilic acid to alter the color of U-V fluorescence (see Teas and Anderson, PNAS 37:645-649, 1951). Apparently, no morphological modification of vegetative or reproductive structures has been associated with Bf.
In 1975, I requested seeds of the Coop's wx Bf stock from Dr. Lambert with the intention of eventually looking at interaction of Pt and Bf. On several of the plants from those seeds, no silks emerged from the ears because--as I discovered too late to use the pollen, and much to my surprise--of Pt-like (sterile) pistil proliferation from both upper and lower ear florets. These plants and all their sibs had been detasseled (to protect a nearby isolation plot) and no sibs were selfed. However, several sibs were used as females in specific crosses.
I found no such Pt-like symptoms on ears from any sibs, nor on any ears on F1's from the sibs. Of 216 F2 plants (a sample aggregate from 21 F1's), all were female fertile, but ears from seven did show lower floret and occasional upper floret pistil proliferation. Though pollination of the F2 ears was not controlled, kernels from the seven ears showing Pt-like symptoms produced blue fluorescent seedlings in high enough proportion to indicate all were homozygous Bf. Only two of the seven apparently were homozygous wx.
A second supply of wx Bf seeds was obtained from Dr. Lambert in 1979. Six-week-old plants from these seeds were partially defoliated (a practice which considerably attenuates Pt expression--perhaps by slowing metabolic rate in developing florets?). All ears "silked" normally, and I was able to self all but two plants. Ears from three of eighteen plants (including an unpollinated one) showed pistil proliferation from lower florets.
Dr. Lambert has indicated that contamination of the wx Bf stock with Pt cannot account for the Pt-like symptoms I am observing. My limited data are consistent with the hypothesis that these symptoms are due rather to a recessive gene which may depend on homozygous Bf for expression. However, other explanations involving variable penetrance (a characteristic of Pt!) cannot yet be ruled out. Dr. lambert's stock number for the 1979 seed sample is 74-853-6. Over the next couple of years, I will be trying to establish a strain (homozygous??, Bf??) from the above-mentioned selfed pistil-proliferating ears which expresses this phenotype at or near the 100% level.
If anyone is aware of published or unpublished examples of similar morphological correlates of Bf, bf2, or any gene other than Pt, please let me know.
Absalom F. Williams
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