Chromosomes and genes of Chinese maize

Since last spring, F1 hybrids between 11 Chinese maize varieties and Wilbur's Flint (New England strain) were grown. Microsporocytes of these hybrids were collected and fixed in aceto-alcohol fixative. Meiotic chromosomes were examined by following standard aceto-carmine squash technique. Now studies of 51 plants from five crosses are complete, and those of the other hybrids are being carried on. Results of the latter will be reported in a late date, and those of the former are in the following:

The Chinese maize varieties employed in the foregoing five crosses were Tuo 229, Feng-1B, Tieh 84, Wu 3025 and Wu 105. The number of chromosome knobs of these five varieties varied from four to eight as shown in Table 1. It is also clear from this table that all of them had a knob on the long arm of chromosomes 4 and 7, either homozygous or heterozygous. In the long arm of chromosome 6, there was at least one knob for the five varieties. In addition, in three of the 10 F1 hybrid plants involving Tuo 229, chromatid bridges without fragments were observed at anaphase I of meiosis. However, no inversions or any other chromosome alterations were identified at pachytene stage. Fusions of knobs and centromeres were always present at pachynema in the 10 F1 hybrid plants involving Feng-1B. In the same hybrids, extrachromosome elements at pachytene stage, laggards, and chromatid bridges at anaphase I were also found. In the 11 F1 hybrid plants having Wu 105 as one parental variety, chromosome stickiness was consistently observed at diakinesis. Usually two, three or more bivalents were stuck together. The points of contact appeared at random. Material exchanges or chiasma-like configurations among the sticky chromosomes were not seen.

All of the above irregularities and knobs are from the Chinese maize, since the chromosomes of Wilbur's Flint were previously known to have no such irregularities and were also known to be practically knobless.

In the fall of 1978, from a selfed progeny of maize strain 7701, 51 seedlings were grown. Among them 32 plants had purple plumule, and the rest green. Even though the sample is small, only 51 individuals, it appears correct to say that the purple plumule character is governed by two pairs of dominant genes Pu1 and Pu2 which function complementarily. The ratio of 32 purple versus 19 green fits well the expected ratio of 9:7 for complementary genes.

Table 1.

Y. C. Ting and Margaret Yu

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

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