Pathways of genetic transfer from Tripsacum to Zea mays.

The cytogenetic interactions in maize x Tripsacum hybrid derivatives can be remarkably complex. The number of viable, somewhat female fertile chromosome combinations is astonishing. Fifty-four different combinations are listed in this paper, and others are certainly possible. In successive backcrosses to maize, chromosome numbers scale both up and down with ease, sometimes stabilizing for a few generations via apomixis, but in most cases finally generate balanced maize genomes and emerge as recovered maize. The maize, however, can produce strange and unusual phenotypes as a result of genetic transfers from Tripsacum. Highly tripsacoid maize lines with 2n = 20 chromosomes were recovered in pathways where the maize genome had first contaminated the Tripsacum genome in early backcross generations. In other pathways interaction of the two genomes is rare. Dominant resistances to six maize diseases were found in BC(8) populations.