An investigation is underway to examine the combining ability of maize inbreds containing various teosinte segments that have been crossed with a Tripsacum addition stock and the normal control. Heterosis is being tested in the field by a three-way yield trial. The first block consists of seven different hybrid combinations of introgressed segments from teosinte within an isogenic background of A158. The second block results from the crossing of seven A158 teosinte derivative lines with a Havels-A158 line carrying a Tripsacum addition disome (Tr7). The third block operates as a control in that it is a cross between the seven teosinte derivative lines and the Havels-A158 line without the Tripsacum chromosome.

The yield of each line is recorded. Then, comparisons between and within the three blocks allow an estimation of hybrid vigor and of general combining ability.

A cytological examination of the hybrids involving the Tripsacum chromosome is made to verify its presence. It was observed in each line in only 50 to 75% of the plants examined, showing reduced transmission in this material.

A further measure of genetic interaction within the hybrids will involve their examination via gel electrophoresis. Kernel proteins as well as isozymes will be investigated. Preliminary results indicate that certain combinations of teosinte and Tripsacum germplasm give a significant increase in yield. The associated electrophoretic study will hopefully quantify this interaction. The lines will also be evaluated in terms of the hybrid dysgenesis syndrome to determine if this process occurs in these hybrids.

This investigation is being undertaken as part of my doctoral research requirements for the Ph.D. degree under supervision of Dr. Walton C. Galinat.

Joel I. Cohen

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