Ploidy level studies on the Dioscorea cayenensis/Dioscorea rotundata complex core set

Abstract

The Guinea yams, Dioscorea cayenensis Lam. and D. rotundata Poir. (D. cayenensis-D. rotundata complex), represent a highly important crop, widely distributed in the humid and semi-humid tropics. The ploidy levels of 170 accessions of the core set of Guinea yams from West African countries was determined using flow cytometry with propidium iodide staining. One hundred and eight of the genotypes were found to be tetraploid, 47 were hexaploid and five were octoploid. One mixoploid individual containing tetraploid and hexaploid nuclei was also detected. A deeper analysis considering each separate taxon revealed that while for D. rotundata the majority of individuals were tetraploid, for D. cayenensis this ploidy level was not detected in any of the accessions. Also, no association between ploidy level and place of cultivation was found for the evaluated germplasm. The obtained data is highly valuable for breeding programs of Guinea yam, especially for the optimization of future hybridization experiments directed to the genetic improvement of this economically important crop.

Genetic structure and diversity in the Dioscorea cayenensis/D. rotundata complex revealed by morphological and isozyme markers

“…rotundata (Obidiegwu et al, 2009b), data were genotyped as binary data (presence = 1 and absence = 0), generating a binary matrix. The morphological data were also analyzed by transforming each character state into a code within each descriptor, and these codes were subsequently transformed into binary data.…”

Isolation and characterization of microsatellites for the yam Dioscorea cayenensis (Dioscoreaceae) and cross-amplification in D. rotundata

“…D. cayenensis and D. rotundata (known as Guinea yams) are the most popular and economically important yams in West and Central Africa (Obidiegwu et al, 2009). In Brazil, these species, also called yellow yams (D. cayenensis) or white yams (D. rotundata), are mainly grown in the Northeast, producing few large tubers per plant (Santos, 2002).…”

“…These species are considered polyploid by most authors (Obidiegwu et al, 2009), although D. rotundata has also been considered diploid by Scarcelli et al (2006). They are dioecious and perennial and are characterized by the presence of herbaceous stems with thorns, climbing habit and edible tubers rich in carbohydrates, vitamins and minerals (Lebot, 2009).…”

Ploidy levels of Dioscorea alata L. germplasm determined by flow cytometry

“…The major advantages of this technique are the convenience, precision and rapidity of the analysis, the requirement of a small amount of tissue, and the ability to analyse large populations of nuclei (Doležel et al 2007). Its application in the analysis of the ploidy level and/or estimation of genome size in Dioscorea has already been demonstrated to be very successful and convenient (Hamon et al 1992;Egesi et al 2002;Obidiegwu et al 2009). …”