Molecular cytogenetic characterization of the native forage grass trichloris crinite

Abstract

Trichloris crinita (Lag.) Parodi is a perennial forage grass native to—and of wide distribution in—arid and semiarid regions of the American continent. In addition to its good forage quality, this species is particularly valued in these drylands due to its high tolerance to drought, salinity, trampling, and grazing. Genetic and cytogenetic information for T. crinita is very scarce, hindering progress in genetic research and breeding of the species. We describe chromosome numbers, karyotypes, heterochromatin distribution, physical mapping of ribosomal DNA (rDNA) genes (18–5.8–26S and 5S) by fluorescent in situ hybridization (FISH), and chromosome pairing in meiotic cells for the first time in T. crinita accessions. Karyotype based on chromosome morphology and cytogenetic landmarks are presented for eight T. crinita accessions. Physical mapping of rDNA loci revealed variation in the number, size, and intensity of the 18–5.8–26S FISH signals, whereas 5S rDNA produced two signals per accession. Considering a basic chromosome number of 10, as reported for most Chloridoideae species and the facts that all 20 T. crinita accessions analyzed had 40 somatic chromosomes, that only bivalent chromosome pairings were observed in meiosis, and that chromosome morphology and sizes revealed high similarity between pairs of chromosomes, along with other reproductive features of the species, strongly suggest that T. crinita is an allotetraploid (2n = 4x = 40). Our cytogenetic data represent a useful resource for advancing cytogenetic research and breeding in T. crinita.