An efficient method for producing trisomic and telotrisomic plants in uniform backgrounds

Self- and sib-pollinated ears of some inbred lines produce occasional grains that are clearly smaller than their neighbors. Following are data obtained from cytological examination of mitoses from root tips of such small kernels germinated in petri dishes:
Inbred lines Kernels
Normal seedlings (no.) Primary trisomics (no.) Monotelo-trisomics
W23 and 3 close derivatives 28 14 4 3 1
N6 8 4 0 2 0

Of the 22 "W23" plants examined, 14 (64%) were normal, 4 (18%) were primary trisomics, 3 (14%) were telotrisomics, and one (5%) was monotelodisomic (i.e., diploid but lacking an arm of one chromosome). Only 6 N6 plants were examined; 2 (33%) were telotrisomic. The trisomic and telocentric chromosomes varied greatly in length, so several chromosomes were likely represented; chromosome 1 was definitely identified.

It appears that the simple procedure of selecting small kernels from inbred ears provides an efficient method for developing trisomic and telotrisomic stocks in uniform backgrounds. If the small kernels have aneuploid endosperms, as seems likely, then it is probable that trisomics of certain chromosomes and chromosome arms will not be selected by this method, because aneuploid endosperms produced by some B-A translocations are approximately normal in size.

The expert assistance of Percy Sallee in all aspects of fixing, staining, and cytological examination of the preparations is gratefully acknowledged.

Jack B. Beckett

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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