OBSERVATIONS ON INTROGRESSION OF TRIPSACUM INTO MAIZE

Derivatives of a cross between diploid Zea mays L. and Tripsacum dactyloides (L.) L. (2n = 72) were compared cytologically and morphologically. The objective of this study was to detect introgression from Tripsacum to maize that might have occurred during seven backcross generations with maize. Thirty-three morphological characters were used to analyze variation among aneuploid (20Zm + 2Td), 20-chromosome recovered maize, and the recurrent maize parent plants. Aneuploid and maize checks were extreme types, with 20-chromosome hybrid derivatives being morphologically intermediate. Several recovered maizes clustered with aneuploid plants and these hybrid derivatives have the greatest chance of Tripsacum introgression. Many traits such as endosperm abnormalities, tassel seed, albinos, tunicate glumes, tassel-tipped ears, fasciated and branched ear, and male spikelets between rows of kernels were observed. Although the genetic basis of many traits is unknown, mutations, epistatic effects or expression of Tripsacum chromatin are possible causes. The number of abnormal and tripsacoid traits observed in 20-chromosome recovered maizes indicates genetic transfer from Tripsacum to the maize genome.