Florida State University
Tom Thumb, a useful popcorn --Bass, HW, Kang, LC, Eyzaguirre, A We have been working with an extra-early yellow popcorn for several years and report here on some of the desirable attributes of this variety called Tom Thumb. Tom Thumb can be propagated by self or open pollination and appears to be a stable inbred. We have adopted Tom Thumb as one of our regular '"lab rats" because of its 1) extremely rapid life cycle, 2) tolerance to greenhouse growth throughout the year in Tallahassee, 3) uniformity of growth habit, and 4) good seed set as shown in Figure 1. The seed are available from the Maize Stock Center, but we routinely work with seed purchased from Johnny's Selected Seeds (johnnyseeds.com, Albion ME). As stated in their 2001 home garden catalog entry on Tom Thumb, "85 days, extra-early, yellow popcorn. Refined from a genuine New Hampshire heirloom by the late Prof. E. M. Meader, University of New Hampshire and Johnny's Selected Seeds. Matures even in the Far North. The plants are dwarf, only 3 1/2' tall, and bear 1 or 2 ears 3-4" long." We counted the leaf bearing nodes for plants (n=43) from the Fall 2000 greenhouse. Node number ranged from 8 to 11 with a mean of 10.

The plants are almost too quick and small for summer fields. They can be grown indoors in small pots at high density with relatively little supplemental lighting. The plants usually produce tillers that can be cut back to assist shoot capping on the main stalk. Tom Thumb offers a number of advantages as an experimental or educational line of maize. For instance, a seed mutagenesis experiment can produce dominant mutations (plant or seed) during a single academic quarter or semester. Also, Tom Thumb might be good for production of transgenic maize using genotype-independent protocols.

We are currently breeding meiotic mutations into the Tom Thumb background for use in our work on meiotic telomere functions. We have examined the pollen mother cells and found them to be suitable for FISH and immunocytochemical analysis of meiotic prophase. Figure 2 shows that telomeres and several knobs can be detected by 3D FISH carried out as previously described (Bass et al., J. Cell Biol., 137:5-18).

We are collecting size-staged anthers of green-house grown Tom Thumb plants. The size classes are "A" < 0.5 mm; "B" 0.5-1.5 mm; "C" 1.5-2.5 mm; and "D" 2.5-3.5 mm. Figure 3 shows DAPI images of representative meiotic nuclei from A, B, and C size classes which contain anthers from premeiotic interphase plus early leptotene, leptotene plus zygotene, and zygotene plus pachytene, respectively. These anthers will provide mRNA preparations for microarray analysis of meiotic gene expression. Anthers from the larger floret are dissected in the greenhouse, measured on a ruler under a dissecting microscope, and frozen. Anthers are collected for four months at a time, then a new set of collections is started. Those shown in Figure 3 are from the first trimester of 2000 (Jan-April).

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