In a preliminary search for photosynthetic pigment differences in leaves of maize and Chalco teosinte by using the technique of thin-layer chromatography as described by Hirayama (J. Biochem. 61(2):179-185, 1967), two pigments were found in maize that were not present in teosinte. With this information it was thought to be worth analysing a larger sample of both maize and teosinte from various regions in Mexico where they grow in sympatry, in order to see to what extent this difference between these plant species is common. During September to October of 1984 and 1985 several trips to the states of Guanajuato, Guerrero, Jalisco, Mexico, Michoacan, Nayarit and Oaxaca were made to collect green leaves from sympatric maize and teosinte plants. A total of 29 paired samples were obtained.

Preliminary tests showed that leaves of 4-5-week old seedlings were as good as those of mature plants for the chromatograms. This allowed us to run pigment analyses on seedling leaves from seed originating both from previous collections from several localities not visited this time and from seed received from other investigators. Among these latter localities were those of the states of Chihuahua and Durango for Mexico, and Huehuetenango and Jutiapa for Guatemala.

The results obtained are as follows: in all maize collections the chromatograms showed the presence of 9 pigments expressed as 9 distinct bands; three pigments differentiated teosinte collections from maize collections. Two of them (pheophytin a and lutein) found in all samples of maize leaves analyzed (29 samples, 232 plants) were absent in those of teosinte (47 samples, 408 plants). A third pigment, not yet well characterized, was found only in the chromatograms of 21 of the 47 teosinte samples, and absent from all maize samples.

In order to learn about the inheritance of two of the differential pigments (pheophytin a and lutein) between maize and teosinte, leaves of F1 and F2 of the cross between an S5 line of the race Conico and a Chalco teosinte, and of its BC1 to maize were chromatographically analyzed. It was found that both pigments present in maize were absent in the F1's chromatograms, indicating absence of pigment as dominant. Furthermore, lutein segregated 3:1 in the F2 and 1:1 in the BC1 progenies, indicating this pigment follows a simple Mendelian inheritance. In the case of pheophytin a, no one F2 or BC1 plant showed the pigment, indicating that its inheritance is more complex and needs further study. Since the third pigment is absent in Chalco teosinte, it was not possible to get any information about its inheritance. However, in two of the teosinte collections from a southwest state of Mexico it was found that the pigment was segregating among different plants, a fact that at least suggests that it is genetically controlled.

All this information has been interpreted in the sense that it constitutes a further evidence in support of the hypothesis postulated, based on chromosome knob data, that between sympatric maize-teosinte populations introgression has not occurred for a long time (probably several millenia) and it is not actually occurring, in spite of the hybridization that constantly produces fertile hybrids. (This investigation has been partially financed by the Consejo Nacional de Ciencia y Tecnologia of Mexico under the grant PCAFBNA-005293).

T. Angel Kato Y. and Mario A. Vargas O.
 
 

Return to the MNL 60 On-Line Index
Return to the Maize Newsletter Index
Return to the MaizeGDB Homepage