Zea diploperennis is a perennial diploid teosinte that was only recently discovered by Iltis in Mexico. It is ancestral to the tetraploid perennial known for over two-thirds of a century earlier from the same general area (southern Jalisco).
The detailed morphology and identification of the individual chromosomes of two collections (H. Iltis and T. A. Kato) of the material is underway. The chromosomes although essentially knobless show strikingly prominent chromomeres terminating one or both the arms. In a few cases where these fuse they give the appearance of very small knobs described by Longley as dimunitive knobs in the 4n perennial.
From the analyzable pachytene preparations, chromosomes six, seven, eight and ten have been identified. In essence the chromosomes of maize and diploperennis are similar, if not identical.
Meiosis is regular. Ten bivalents are formed. In a few instances nine bivalents and two univalents are noticed. Chromosome distribution at anaphase is normal with sporadic occurrence of laggards.
Contrary to expectations the diploid has larger pollen than the tetraploid. The pollen of the 2n is similar in size to the pollen of Guatemalan teosinte and that of primitive corn (Chapalote).
The 2n is more primitive than the 4n in being a stronger perennial. The 2n develops enlarged underground buds (tuber-like) that may remain dormant for a month or more while the 4n is in a state of continuous growth. Even the F1 hybrid with corn has a month to six-week dormancy period between the maturation of the plant and appearance of a basal flush of tillers. At first the F1 hybrid may appear to be annual like its corn parent but patience by the observer shows this not to be the case. Studies on the inheritance of perennialism will be complicated by this dormant behavior.
In contrast to the paired female spikes of the annual teosintes, the 2n perennial usually has solitary spikes like most corn. In the 2n hybrid of diploperennis with corn, both the spikes and spikelets tend to be paired.
Diploperennis has potential for the development of new types of corn. Like corn, it is not winter hardy in northern United States, despite its adaptation to high elevations in Mexico. The dormancy factor might help it to overwinter in southern United States.
Walton C. Galinat and Chandra V. Pasupuleti
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