Notes on Zea luxurians (Durieu) Bird and some requests

Since the teosinte race often called Guatemala was renamed as a third species of Zea (Taxon 27:363, 1978), further evidence has become available which affects the delineation of that species. Z. luxurians differs from maize and Mexican annual teosinte in many more ways than at first understood, but the Honduras population which was tentatively included in the species must be excluded, as must the cytologically similar Huehuetenango race of northwest Guatemala.

A recent paper by Timothy, Levings, Pring, Conde and Kermicle (PNAS 76:4220, 1979) describes the agarose gel electrophoretic patterns obtained from restriction endonuclease digests of chloroplast DNA and mitochondrial DNA. Three endonucleases were used on ctDNA and four on mtDNA. Z. luxurians differed in all seven cases from Z. mays and Z. mexicana, including Huehuetenango, sometimes by many bands. It was identical to Z. perennis in three digests of ctDNA, none of the mtDNA. Huehuetenango was identical to a northwest Balsas sample from Michoacan in all seven cases. These were identical to either maize or Mexican annual teosinte in each case. However, the sampling per race was very narrow.

Over the past year, we have grown small samples of a wide range of teosinte materials, partly to obtain morphological specimens, partly for genetic purposes. The tassels from these have been examined with particular attention being paid to the spikelets. Iltis (26th Annual Systematics Symposium of the Missouri Botanical Garden, abstracts, 1979) states that Z. luxurians, Z. perennis and Z. diploperennis differ greatly from maize and Mexican annual teosinte, and using male spikelet morphology, he and Doebley (in press) are splitting the genus into Sect. Luxuriantes, with the first three species, and Sect. Zea with the last two taxa condensed into Zea mays. We lack specimens of Z. perennis and Z. diploperennis, but Z. luxurians is certainly very different.

The lower or outer glumes of the Z. luxurians tassel spikelets have two prominent angles or ridges with one or more veins bearing hairs, between which there are about 15 veins spread across the flattened surface. Those of maize and the Nobogame, Chalco, Balsas (Mazatlan) and Huehuetenango teosinte races, at least, have 1-6 veins on a more rounded surface between obtuse angles bearing shorter hairs. In Z. luxurians the pedicels of the pedicellate spikelet are fused to the branch rachis for about 1 mm; the branch rachises are usually 1.0 mm or more broad with prominent abscission creases below the nodes; and the nearly unbranched primary branches form very narrow angles with the main rachis. In the maize and Mexican annual teosinte which we examined, the pedicellate spikelets are free of the branch rachis; these rachises are usually less than 1 mm broad; abscission creases are absent, not visible or not prominent; and the primary branches usually form wide angles with the main rachis. Nearly always there are many 20 and 30 branches. Further differences have been noted, but these are sufficient to allow characterization of specimens. Four samples from southeast Guatemala (PI 306615, 306616, 306617 and 343231) can be identified as Z. luxurians; the first may be the most free of maize introgression. Our one sample of Florida teosinte also has the Z. luxurians form, but the one sample of Honduras teosinte which we grew definitely has the other form.

The morphology of the teosinte fruit-case or alicole, including the cupule and spikelets, has been noted by several investigators to indicate not only some major divisions between races, but also introgression from maize. The Honduras teosinte sample we have has very maizoid alicoles--many have two spikelets indicating that maize or a maizoid teosinte has had a great influence on it.

A further correction--all Z. luxurians examined has a recognizable central spike in the tassel, sometimes a little thicker than the primary branches with three ranks of spikelet pairs. Usually primary tassel branches are decussately arranged on the main rachis giving four ranks; five ranks of solitary branches have been seen.

We would like very much to have specimens of other collections of Z. luxurians and its seeming nearest relatives, the Huehuetenango and Honduras populations, Z. perennis and Z. diploperennis, for comparison. Of special interest would be specimens of Florida teosinte so that we can check whether that material, which so often has represented Z. luxurians in genetic experiments, is a good representative. Plants which seem to be the product of hybridization with maize are reported in the populations in Guatemala, and some of our Z. luxurians plants have varied in the direction of Z. mays or Z. mexicana. Perhaps a measure of such a tendency could be used as a factor in interpreting genetic experiments. Tassels and ear branches (especially from the 7th node from the tassel) would be appreciated, picked when flowering, if possible (please send them to the first author, P.O. Box 9983, Kirkwood, MO).

Robert McK. Bird and Jack B. Beckett*

*USDA-SEA, University of Missouri, Columbia


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