Chromosome-knob constitutions were determined in several plants of diploid perennial grown at Chapingo from seed collected at San Miguel, Sierra de Manantlan in the state of Jalisco, and also observations in this regard were made in plants of the tetraploid perennial teosinte of Cd. Guzman, Jalisco.
The tetraploid plants were almost knobless and only showed terminal small or very small (large chromomeres) knobs on the pachytene chromosomes. No attempts have been made to determine which chromosomes possessed them. Surprisingly, the diploid plants appeared to be different, since small and medium-size knobs were present in many chromosomes, all knobs being terminally located. Knobs were found on the following chromosome arms: small knobs on 1S, 2S, 2L, 3S, 4L, 5S, 5L, 6L, 7L, and 8L; medium knobs on 2S, 3S, 3L, 5L, 6L, 7L, 8L, and 9L. In neither case were abnormal chromosome-10 and B-type chromosomes nor internal knobs observed.
These preliminary results seem to suggest that the diploid perennial teosinte from the Sierra de Manantlan is similar to the southern Guatemala teosinte regarding the knobbed positions, although the latter has larger knobs than the former.
T. Angel Kato Y.
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