Farmers’ perspective toward a demand led yam breeding in Nigeria

Open Access JournalThis study seeks to increase the efficiency of yam breeding practice using farmers’ insight at the trait and socioeconomic levels. A three-staged multisampling procedure was employed and 792 yam farmers from four geopolitical zones, comprising 10 states and the Federal Capital Territory, Abuja in Nigeria were randomly selected. Farmer’s preference criteria and factors pertinent to improving the efficiency of yam breeding in Nigeria were documented. The data obtained were analyzed using a 5-point Likert scale to identify major traits farmers consider in the yam cultivar selection decision. Kendall’s coefficient of concordance was used to measure the degree of agreement of ranking among the farmers. Factors influencing farmers’ trait preference for yam cultivars were evaluated using a multinomial-ordered logistic regression model. The result revealed that yam varieties with high germination rates, disease-free quality, big tuber sizes, early maturity, and good pounding attributes are held in high esteem. The most critical constraint limiting the production of yam in the study area includes pest and disease attack, climate change, high cost of seed yam, high cost of staking, and weed infestation. Sex, age, access to credit, membership to yam association, total land owned, and years of experience as a yam farmer significantly influence farmers’ ability to select yam cultivars with preferred attributes. A strategic effort needs to be given to these farmers’ desired yam attributes and factored into developing improved yam varieties for increased adoption and enhanced food security in Nigeria

SSR markers reveal diversity in Guinea yam (Dioscorea cayenensis/D. rotundata) core set

The genetic diversity of 219 accessions of Guinea yam germplasm from Benin, Congo, Côte d’ Ivoire,Equatorial Guinea, Gabon, Ghana, Nigeria, Sierra Leone and Togo was accessed using 15 microsatelliteloci. High diversity of 0.677 was found among the accessions. An allelic average of 8.06 andpolymorphic information content (PIC) value of 0.65 was observed for the markers. The observedheterozygosity value of 0.563 suggests that spontaneous hybridization must have contributed to theancestry of some of the accessions and improvement by farmers must have been far more often byselection of somatic mutants. The twenty distinct cluster groups generated by the radial phylogramshows that Dioscorea cayenensis and D. rotundata are distinct species with intermediate hybrid forms.There was no relationship between relatedness of the accessions and their geographical area of origin.This study contributes to an increased understanding of the genetic organisation of the coregermplasm

Genetic characterization of some water yam (Dioscorea alata L.) in West Africa with simple sequence repeats

A collection of 89 water yam (Dioscorea alata L.) accessions from Benin, Congo, Côte d’Ivoire, Equatorial Guinea, Gabon, Ghana, Nigeria, Sierra Leone and Togo was assessed for genetic diversity using thirteen microsatellite loci. These 89 are some of the D. alata accessions conserved by the International Institute of Tropical Agriculture (IITA) Ibadan, Nigeria. A total of 97 alleles were detected with an average allele number of 7.46 per locus. Polymorphism information content (PIC) mean value of 0.65 showed existence of variability among the accessions. Accessions from Nigeria showed highest gene diversity of 0.678 while those from Côte d’Ivoire had lowest diversity with 0.596. Observed mean heterozygosity value of 0.469 was observed. Cluster and principal coordinate analysis showed 8 major cluster groups. There was no relationship between relatedness of the accessions and their geographical area of collection. SSR markers proved to be effective to characterise studied D. alata germplasm

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

The Guinea yams, Dioscorea cayenensis Lam. and D. rotundata Poir. (D. cayenensis–D. rotundata complex), represent a highly importantcrop, widely distributed in the humid and semi-humidtropics. 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 nucleiwas 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 cro

Estimation of the nuclear DNA content in some representative of genus Dioscorea

Nuclear DNA content of 54 accessions of 6 Dioscorea species collected from West African countries were determined using flow cytometry. Observed ploidy levels are diploid (2x), triploid (3x), tetraploid (4x), hexaploid (6x) and octoploid (8x). DNA index varied from 0.36 to 1.54 depending on the cultivar and considered specie. Estimated nuclear DNA sizes ranged from 0.702 ± 0.004 pg for G1 nuclei of diploid Dioscorea dumetorum to 2.573 ± 0.020 pg for G1 nuclei of octoploid Dioscorea cayenensis. Our result showed that there is a decrease in genome size with higher ploidy level. The study contributes a step towards a genome understanding of this group of plant

Chromosome evolution and the genetic basis of agronomically important traits in greater yam

The nutrient-rich tubers of the greater yam Dioscorea alata L. provide food and income security for millions of people around the world. Despite its global importance, however, greater yam remains an “orphan crop.” Here we address this resource gap by presenting a highly-contiguous chromosome-scale genome assembly of greater yam combined with a dense genetic map derived from African breeding populations. The genome sequence reveals an ancient lineage-specific genome duplication, followed by extensive genome-wide reorganization. Using our new genomic tools we find quantitative trait loci for susceptibility to anthracnose, a damaging fungal pathogen of yam, and several tuber quality traits. Genomic analysis of breeding lines reveals both extensive inbreeding as well as regions of extensive heterozygosity that may represent interspecific introgression during domestication. These tools and insights will enable yam breeders to unlock the potential of this staple crop and take full advantage of its adaptability to varied environments