CYTOGENETIC STUDY ON Tripsacum GENUS

Abstract

This study was carried out to determine chromosome number and ploidy level of 14 different species of genus Tripsacum collected by the International Maize and Wheat Improvement Center (CIMMYT) in México and other american countries, and kept at Tlaltizapán, State of Morelos, México. Samples of seedlings were taken from 187 plants (collection size: 203 plants) and they were maintained during four weeks or more under greenhouse conditions at CIMMYT, El Batán, Texcoco, México. Root tips were obtained from each plant and kept in a mitosis promoter solution for four hours; later on they were kept at 5 °C. Carmin-acetic were used to stain radicle tissues. Chromosome count numbers were determined for mitotic cells during metaphase in at least 10 cells for each plant sample; unusual count numbers (2n= 54; 2n= 64) were verified, running additional observations. Most of the species (10 out of 14) were tetraploids and T. dactyloides hispidum had the highest frequency (79 plants). Plants for T. maizar and T. zopilotense showed three ploidy levels (2X=36, 3X= 54, 4X=72). T. australe, T. dactyloides dactyloide and T. peruvianum exhibited only diploids.