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:
|Normal seedlings (no.)||Primary trisomics (no.)||Monotelo-trisomics
|W23 and 3 close derivatives||28||14||4||3||1|
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
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