CITOLOGÍA DE ESPECIES DE GRAMÍNEAS EN EL NORTE-CENTRO DE MÉXICO

Abstract

This study was carried out with populations of Distichlis spicata (L.) Greene, present in north-central Mexico (Durango, San Luis Potosi and Zacatecas) and Reederochloa eludens Soderstr. & Decker, two related taxa sympatric in this region of Mexico. Previous cytological investigations about these taxa are restricted to chromosome counts, but considering their ecological and economic importance (genera of alkaline areas and forage quality), as well as the recent inclusion of both taxa in the genus Distichlis based on morphological, anatomical and molecular characters, we decided to contribute to the knowledge of their relationships and taxonomic patterns by a cytological study. These two taxa have the particularity to survive in soils with high salt content. This work was carried out in the laboratory of Citogenética CIIDIR-DGO, IPN. The chromosome preparations were performed under the crushed or squash method using root meristematic tissue of plants collected from their natural habitats, then rooted and kept under greenhouse conditions. After pretreatment steps, fixation, hydrolysis, Squash, and assembly, it was proceded to the observation, measurement and karyotype analysis. The main results are: 1) The basic number x = 9 or x = 10 for D. spicata and x = 9 for R. eludens are confirmed. 2) The first report of tetraploidy for D. spicata is presented (2n=4x=36 and the tetraploidy 2n=4x=40 is confirmed), as well as tetraploidy + aneuploidy for R. eludens (2n=4x+2=38) are confirmed. 3) The first report of tetraploidy 2n=4x=36 for R. eludens is presented here. 4) The chromosomes observed in the karyotypes are metacentric and submetacentric, very homogeneous among species and among populations. 5) The total length of chromosomes varies between 36.66 and 55.95 μm, the shorter ones (0.19 to 1.08 μm) in R. eludens and the longer (0.35 to 1.44 μm) in D. spicata. 6) We report a new locality for Reederochloa eludens, found in Zacatecas. 7) Reederochloa is recognized as part of Distichlis based on similarities in their chromosomal characteristics (TF% CI, LTC), which indicate a close relationship between them.