Determination of ploidy among Yam (Dioscorea spp.) landraces in Kenya by flow cytometry

Abstract

Yam (Dioscorea spp.), a traditional crop in Kenya has not undergone improvement and little has been done to understand its genetic background. The taxonomy and phylogeny of the local landraces has not been fully studied. The main cultivated species is Dioscorea minutiflora Engl. Others found with low distribution are Dioscorea alata L., Dioscorea bulbifera L. and Dioscorea odoratissima Pax. Flow cytometry was used to estimate the ploidy level of 155 accessions of Kenyan yam including two checks, TDr.18544 a tetraploid and TDc 98/136 an octoploid from International Institute of Tropical Agriculture (IITA), Nigeria. Also included in the study were Dioscorea dumetorum Pax, Dioscorea asteriscus Burkill and Dioscorea schimperiana Kunth which are yam wild relatives. Leaf samples were harvested from the field genebank and nuclei extracted using an extraction buffer (Partec GmbH, Munster Germany). Plant nuclei were isolated and stained with propidium iodide then analyzed in a flow cytometer. Seven ploidy levels of 3x (11.4%), 4x(37.5%), 5x(29.2%), 6x(14.6), 7x(3.1%); 8x(3.1%) and 10x(0.6%) were observed. Tetraploids (4x) formed the highest proportion followed by pentaploids (5x). The highest ploidy, decaploid, (10x), was found in D. odoratissima Pax, a conspecific form of Dioscorea preahensilis found under cultivation in two farms in Western Kenya. No diploids were observed in the study. Ploidy level was not associated with geographical habitat of the landraces while farmer-named varieties were not associated with ploidy levels. The findings generated new knowledge and form a basis for future yam research and improvement in the country. Further work is required to establish the phylogeny of Kenyan yam landraces.

Yam (Dioscorea spp.) production trends in Cameroon: A review

“…The ploidy levels include diploid (D. dumetorum), tetraploid (D. cayenensis, D. rotundataand D. alata), hexaploids (D. alata and D. rotundata) and octoploids (D. cayenensis) (Ngo-Ngwe et al, 2014). Contrary to previous reports of triploids, pentaploids or octoploids among D. alata collections from Chad, Puerto (Muthamia et al, 2014) and IITA Ibadan (Obidiegwu et al, 2009b); Cameroon accessions lack these ploidy levels. Furthermore, only diploids have been reported among D. dumetorum collection in Cameroon (Ngo-Ngwe et al, 2014), yet Obidiegwu et al (2009a), reported the existence of triploids in IITA collection.…”

Genetic Characterization of Water Yam (Dioscorea alata L.) and Production Constraints of Yam in Pwani Region and Unguja Island, Tanzania

“…Ten SSR markers used in this study and the detected 40 alleles are enough to estimate the genetic diversity within the population (Tostain et al 2007, Otoo et al 2015. YM30, Dab2D06, Dab2C05 and Da1A01 were the markers that gave a higher number of alleles in this study, similar to Muthamia et al (2013) and Obidiegwu et al (2009). Dpr3D06 and Dpr3F04 markers gave the lowest number of alleles (2), suggesting their monomorphism, a similar observation to Massawe and Temu (2023).…”

“…Microsatellites are also good enough (powerful) to capture genetic diversity information and provide a highlight of genetic resources available in any germplasm. Other researchers also adopted SSR markers to assess the genetic diversity of yam from different geographical regions (Obidiegwu et al 2009, Siqueira et al 2012, Muthamia et al 2013, Arnau et al 2017). This study aimed to assess the morphological and genetic diversity of water yam (D. alata) and the general production constraints of yam in Pwani and Unguja island.…”

Morphological and molecular characterization of cultivated yam (Dioscorea species) in selected counties in Kenya

“…Molecular studies done on Kenyan yams have been minimal. Previous studies have investigated the genetic diversity using polymorphic Simple Sequence Repeats (SSR) markers that distinguished the landraces Muthamia et al (2013) and ploidy levels; this revealed variable ploidy levels among the local yam landraces (Muthamia et al, 2014) and not the phylogeny of the species. Both studies recommended further work on the phylogeny of Kenyan yams.…”