Background Consumers preferences for food crops are guided by quality attributes. This study aimed at deciphering the genetic basis of quality traits, especially tuber flesh color (FC) and oxidative browning (OB) in Dioscorea alata, based on the genome-wide association studies (GWAS) approach. The D. alata panel was planted at two locations in Guadeloupe. At harvest, the FC was scored visually as white, cream, or purple on longitudinally sliced mature tubers. The OB was scored visually as the presence or absence of browning after 15 minutes of exposure of the sliced samples to ambient air. Results Phenotypic characterization for FC and OB of a diverse panel of D. alata genotypes highlighted significant variation within the panel and across two locations. The genotypes within the panel displayed a weak structure and could be classified into 3 subpopulations. GWAS identified 14 and 4 significant associations for tuber FC and OB, respectively, with phenotypic variance, explained values ranging from 7.18 to 18.04%. Allele segregation analysis at the significantly associated loci highlighted the favorable alleles for the desired traits, i.e., white FC and no OB. A total of 24 putative candidate genes were identified around the significant signals. A comparative analysis with previously reported quantitative trait loci indicated that numerous genomic regions control these traits in D. alata. Conclusion Our study provides important insights into the genetic control of tuber FC and OB in D. alata. The major and stable loci can be further utilized to improve selection in breeding programs for developing new cultivars with enhanced tuber quality.

Yams are important tubers widely consumed in developing countries in various forms, mainly boiled, pounded and fried. Tuber quality is a key criterion for acceptance by the various actors in the value chain. However, the genetics of yam tuber quality has not yet been comprehensively investigated. Given this lack of knowledge, we used population genomics and candidate gene association approaches to unravel the genetic basis of the three main quality attributes of boiled yam, namely texture, starch content and colour indices. We re-sequenced the whole genome of 127 yam genotypes with different quality attributes and performed an enrichment of the already available functional genome annotation using comparative genomics. Population genomics analysis highlighted three main genetic groups and 1,053 genes under selection. We focused this work on three known quality trait-related pathways: pectin, starch content and flavonoid biosynthesis, and inventoried in the genome all the structural genes related to those pathways by comparative genomics. We improved the functional annotation of the three pathways with 48% more genes. A total of 18 candidate genes containing genetic variants significantly associated with the target traits were detected, including eight genes that were also found under selection. The texture-related candidate genes were distributed between the pectin and starch pathways. Overall, the use of comparative genomics has allowed the generation of an unprecedented genomic resource. The improved functional annotation of the yam genome is a promising predictive tool for identifying other core genes associated with any trait of interest to meet the growing need and diversified demands for yams.

Background: Microsatellite markers represent a low-cost and efficient tool for rapid genotyping as compared to single nucleotide polymorphism markers in laboratories with limited resources. For the economically important yam species widely cultivated in developing countries, very few microsatellite markers are available and no marker database has been developed to date. Herein, we conducted a genome-wide microsatellite marker development among four yam species, identified cross-species transferable markers, and designed an easy-to-use web portal for the yam breeder community. Results: The screening of yam genomes resulted in 318,713; 322,501; 307,040 and 253,856 microsatellites in Dioscorea alata, D. rotundata, D. dumetorum, and D. zingiberensis, respectively. Mono-, di- and tri-nucleotides were the most important types of repeats in the different species and a total of 864,128 primer pairs were designed. Furthermore, we identified 1170 cross-species transferable microsatellite markers. Among them, a subset of 17 markers were experimentally validated with good discriminatory power regarding the species and the ploidy levels. Ultimately, we created and deployed a dynamic Yam Microsatellite Markers Database (Y2MD) available at http://yamdb.42web.io/. Y2MD is embedded with various useful tools such as JBrowse, Blast, insilicoPCR, and SSR Finder to facilitate the exploitation of microsatellite markers in yams. Conclusions: The present work is the first comprehensive microsatellite marker mining across several yam species and will contribute to advance yam genetic research and marker-assisted breeding. The released user-friendly database constitutes a valuable platform for yam breeders, especially those in developing countries. Keywords: genotyping; Dioscoreacea; database; microsatellite; transferable markers

Background: Greater yam, Dioscorea alata L., is a significant food security crop in tropical areas. However, low genetic diversity and various biological constraints, including susceptibility to viruses, ploidy, erratic and low flowering intensity, and asynchronous flowering hinder successful hybrid development and genetic gains in greater yam breeding programs. Therefore, pollen storage has gained much attention to facilitate genetic material exchanges, artificial pollinations and to increase the genetic gains in breeding programs. This 4-year study aimed at developing a practical long-term pollen storage technique for the successful development of yam hybrids. Fresh pollens were collected from two D. alata males, then lyophilized (two lyophilization treatments were applied), followed by storage at room temperature (24-25 oC) for 12 months. Moreover, the lyophilized and stored pollens were tested for viability by crossing with four female varieties. Results: Our results showed that lyophilization is effective for achieving viable pollens after 12 months of storage. Treatment 1 (48 h drying) showed higher pollen germination and fertility rates than Treatment 2 (72 h drying). Although we observed a reduction in viability of lyophilized pollens after 12 months of storage, we generated hybrid seedlings with success rates from 12 to 21% compared to 21-31% when using fresh pollens. Paternity testing based on molecular genotyping confirmed the hybrid status of the obtained seedlings, which grew well in a greenhouse. Conclusions: The results signify the importance of pollen lyophilization for yam breeding programs.