From teosinte to maize II
--Luiz Eugênio Coelho de Miranda, Luiz Torres de Miranda and Omar Vieira Villela

In the preceding report a biometric model mapping the case in which two pairs of alleles affect the same characters was applied to Langham's F2 data from crosses of teosinte to maize markers. Tr and pd are duplicated in the same chromosome. In MNL61:29-31 data were presented for crosses of Portugues Fasciado with the standard translocations in IAC Maya, backcrossed to IAC Maya wx. With data of Table 1 in that note, we reanalyzed using the new model for the backcross case. The formulae for repulsion were applied to all data with krn and fas, see Miranda et al. (MNL64:35-36, 1990), p=(a+b)/n, q=(a+c)/n, and for coupling p=(c+d)/n, and q=(b+d)/n. The only case in which consistent results were obtained was for the translocation at 7L.63, for which the results in repulsion transformed into centimorgans are presented.
53.7±5.9 T 9.6±2.8 krn7
fas17 53.7±5.9 T 6.0±2.2 fas7
krn17 60.2±6.4 wx 6.0±2.8 krn7
fas17 60.2±6.4 wx 6.0±2.8 fas7

The T wx recombination of p=39.5 was excessively large and ignored in what follows. In MNL62:38-39, 1988, p was calculated as 1.39±0.49 with data of Anderson et al. (MNL39:106-109, 1965). Also the K7S is terminal in the position in Kato's knob map.

K7L was mapped in Miranda and Miranda (MNL61:34-35) in position 64 with Cateto Palha Roxa.

In MNL52:142, 1978, J. B. Beckett, JB et al. present a cytogenetic map which shows one of the zones of interest, krn7 paralleling and showing position 64 corresponding to 7L.63 in the cytogenetic map. So we have plenty of points of reference to anchor our analysis results.

The data presented here are independent from those and lead to the steps indicated below.

The krn17 fas17 distances were gotten as a mean from T and wx markers. T to wx distance was gotten from the cited report. fas7 to krn7 was obtained as a single comparison, by difference.

fas7 to krn7 was gotten as the difference wx krn7 - wx fas7, giving the distances krn17 fas17 - 57±3.1 - T - 1.5±0.5 - wx - 6.0±1.6 - fas7 - 1.8±4.7 - krn7.

Anchoring it in the distal knob in position 7S.0 in Kato's cytogenetic knob map we get in a working map:
krn17 fas17                               T       wx          fas7 krn7
0                                               57       58.5        64.5  66.3

Only chromosomes 6, 8 and 10 have a string of knobs. The others have only one knob site in each arm. Each knob of a string must have come from a different domestication, and their distribution study will lead to the original cradles. 

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

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