Effect of Different Essential Oils on the Properties of Edible Coatings Based on Yam (Dioscorea rotundata L.) Starch and Its Application in Strawberry (Fragaria vesca L.) Preservation

Every year the world loses about 50% of fruits and vegetables post-harvest and in the supply chain. The use of biodegradable coatings and films with antioxidant properties has been considered an excellent alternative to extend the shelf life of food. Therefore, the objective of this work was to develop a coating based on yam (Dioscorea rotundata L.) starch-containing lime, fennel, and lavender essential oils to extend the shelf life of strawberries (Fragaria vesca l.). The tensile properties, barrier properties (water vapour permeability (WVP) and oxygen permeability (OP)), moisture content, water-solubility, absorption capacity, water contact angle, optical properties, the antioxidant activity of the resultant starch-based coatings were evaluated. After that, the active properties of the coatings were assessed on strawberries inoculated with Aspergillus niger during 14 days of storage at 25 °C. The results showed that the incorporation of essential oils improved the elongation and WVP and provided antioxidant capacity and antimicrobial activity in the films. In particular, the essential oil of lime showed higher antioxidant activity. This fact caused the unwanted modification of other properties, such as the decrease in tensile strength, elastic modulus and increase in OP. The present study revealed the potential use of lime, fennel, and lavender essential oils incorporated into a polymeric yam starch matrix to produce biodegradable active films (antioxidant and antimicrobial). Obtained films showed to be a viable alternative to increase the shelf life of strawberries and protect them against Aspergillus niger.

Identification of quantitative trait nucleotides and candidate genes for tuber yield and mosaic virus tolerance in an elite population of white guinea yam (Dioscorea rotundata) using genome-wide association scan

Background Improvement of tuber yield and tolerance to viruses are priority objectives in white Guinea yam breeding programs. However, phenotypic selection for these traits is quite challenging due to phenotypic plasticity and cumbersome screening of phenotypic-induced variations. This study assessed quantitative trait nucleotides (QTNs) and the underlying candidate genes related to tuber yield per plant (TYP) and yam mosaic virus (YMV) tolerance in a panel of 406 white Guinea yam (Dioscorea rotundata) breeding lines using a genome-wide association study (GWAS). Results Population structure analysis using 5,581 SNPs differentiated the 406 genotypes into seven distinct sub-groups based delta K. Marker-trait association (MTA) analysis using the multi-locus linear model (mrMLM) identified seventeen QTN regions significant for TYP and five for YMV with various effects. The seveteen QTNs were detected on nine chromosomes, while the five QTNs were identified on five chromosomes. We identified variants responsible for predicting higher yield and low virus severity scores in the breeding panel through the marker-effect prediction. Gene annotation for the significant SNP loci identified several essential putative genes associated with the growth and development of tuber yield and those that code for tolerance to mosaic virus. Conclusion Application of different multi-locus models of GWAS identified 22 QTNs. Our results provide valuable insight for marker validation and deployment for tuber yield and mosaic virus tolerance in white yam breeding. The information on SNP variants and genes from the present study would fast-track the application of genomics-informed selection decisions in breeding white Guinea yam for rapid introgression of the targeted traits through markers validation.

Diversity of white Guinea yam (Dioscorea rotundata Poir.) cultivars from Benin as revealed by agro-morphological traits and SNP markers

White Guinea yam (Dioscorea rotundata Poir.) is indigenous to West Africa, a region that harbours the crop's tremendous landrace diversity. The knowledge and understanding of local cultivars’ genetic diversity are essential for properly managing genetic resources, conservation, sustainable use and their improvement through breeding. This study aimed to dissect phenotypic and molecular diversity of white yam cultivars from Benin using agro-morphological and single nucleotide polymorphism (SNP) markers. Eighty-eight Beninese white Guinea yam cultivars collected through a countrywide ethnobotanical survey were phenotyped with 53 traits and genotyped with 9725 DArT-SNP. Multivariate analysis using phenotypic traits revealed 30 traits as most discriminative and explained up to 80.78% of cultivars’ phenotypic variation. Assessment of diversity indices such as Shannon–Wiener (H′), inverse Shannon (H.B.), Simpson's (λ) index and Pilou evenness (J) based molecular and phenotypic data depicted a moderate genetic diversity in Beninese white Guinea yam cultivars. Genetic differentiation of cultivars among country production zones was low due to the high exchange of planting materials among farmers of different regions. However, there was high genetic diversity within regions. Hierarchical clusters (HCs) on phenotypic data revealed the presence of two groups while HCs based on the SNP markers and the combined analysis identified three genetic groups. Our result provided valuable insights into the Beninese white Guinea yam diversity for its proper conservation and improvement through breeding.

Collection, Characterizaton and Conservation of Genetic Resources of Yam Cultivars From Ekiti State, Nigeria

This study was initiated to restore the genetic resources of yam which had been decimated in a core yam-producing community in Ekiti State, Southwestern Nigeria. Twenty cultivars, consisting of Dioscorea rotundata, D. cayenensis, D. alata, and D. dumetorum were identified, collected, characterized and multiplied using an On-farm Participatory Method. The yam cultivars were characterized for quality and yield of pounded yam (iyan) as well as starch properties. They were later conserved in the Teaching and Research Farm of the Obafemi Awolowo University Ile-Ife.Morphological characterization separated Dioscorea alata (Ewura) by its winged vines while Dioscorea dumetorum (Esuru) was separated by its pubescent spines, trifoliate leaf with acute apex and base and the clustered, irregularly-shaped tuber. All the tubers of the yam cultivars had high storability. Pounded yam quality rated the Ikumo and Ajimokun cultivars as best while Odo was rated average and this was attributed to the swelling properties and amylose content of these cultivars. Yam cultivars with high granules had low swelling capacities. The Brittle Fraction Index of the starch from all the cultivars was lower than 1.0 explaining why the iyan they produced had no crust on the surface and kept for long hours after preparation.From this study, it was concluded that the local yam cultivars collected represent the core of yam genetic resources for utilization in the region. These cultivars are therefore recommended for prioritization in further studies on propagation, conservation and improvement so that a narrow genetic base of cultivars is not encouraged, for example, by promoting cultivars whose vines perform well in tuberization.

Variation in Tuber Dry Matter Content and Starch Pasting Properties of White Guinea Yam (Dioscorea rotundata) Genotypes Grown in Three Agroecologies of NIGERIA

The primary objective of this study was to assess the effects of genotype (G), location (L), and G × L interaction on tuber quality traits (dry matter content and starch pasting parameters) in white Guinea yam (Dioscorea rotundata Poir.). Variability in tuber dry matter and starch pasting properties was examined using 18 advanced breeding lines and two dominant landrace cultivars of white Guinea yam grown in three different agroecological zones (forest‒savanna transition, southern Guinea savanna, and rainforest) in Nigeria. The starch pasting properties were evaluated using a Rapid Visco Analyser. Our results show that the G × L interaction effect was low compared to the genotype and growing location effects on the variability of key starch properties. In addition, the repeatability of trait performance across locations was high and relatively uniform for key traits, suggesting that any of the three locations used in this study can be employed for their evaluation. Furthermore, TDr1100873 had a higher dry matter content than the dominant landrace cultivars (Amula and Meccakusa) but was similar to them in starch pasting properties. Hence, TDr1100873 is considered a suitable variety for future breeding activities.

The Impact of Conservation Agriculture Practice and Socio-Economic Factors on Yam Production (Dioscorea alata and Dioscorea rotundata) in Kalagoé (Lobaye, Central African Republic)

Few studies have been carried out on Yam (Dioscorea alata and Dioscorea rotundata) in relation with the conservation agriculture in CAR. Yam is cultivated in limited quantities despite its role in improving food security. In order to increase Yam production in the smallholder farms in CAR, the potential effect of crop management practices like nutrient application, mulching and minimum tillage on Yam crop yield and household financial returns, needs to be understood. A questionnaire was prepared and used as a tool for the collection of information from 100 producers of Yam without distinction of ages and sexes. In order to determinate the agronomical performance of Yam, two plots were explored. The first plot with 625m² (12.5m ×50m), known as the improved plot, is a plot on which all conservation agriculture practices were applied. The second plot, known as the traditional plot, is one on which traditional farming techniques were applied. The results of the survey show that 32% of the farmers are in favor for CA practice nevertheless 68% are not favor, which shows that a large proportion of farmers in Kalangoé are not aware of the benefits of this technique. The most widely cultivated variety is D. rotundata, because of its taste qualities. Some producers also grow both varieties at the same time. Some producers (28%) clear their plots by cutting down all the trees to leave the field bare, while a large number (72%) practice partial cutting by removing the shrubs to keep the large trees in order to protect the forest. A large number of producers (62%) also burn their plots for various reasons, including freeing up space and making it easier to move around the field because the plant debris from clearing prevents them from working properly. A small proportion of producers (26%) practice ploughing against 74% who do not practice this technique. The conservation agriculture practice applied to Yam gave interesting agronomic performances (growth and production parameters) than the farmers practices.

Evaluation of Yield and Resistance Effect of Some Yam Genotypes (Dioscorea rotundata Pior) to Pest Attack at Harvest in Uyo, Southeastern Nigeria

Two years study was carried to assess level of resistance to yam beetle and termite attack by some yam genotypes in Uyo, southeastern Nigeria. The experiment was laid out in randomized complete block design replicated three times. The five yam genotypes tested for yam beetle and termite attack at harvest were; TDr 95/19127, 95/18894, 95/19531, 75/1/2 and Uyo popular local variety eteme. The results showed variations in yield and susceptible to termite and beetle attack at harvest. The TDr 75/1/2 had highest yield 30.41 and 29.75t/ha, followed by TDr 95/18894, 28.86 and 27.93t/ha in 2008 and 2009 respectively. The local variety had lowest yield 9.75 and 10.07 t/ha in 2008 and 2009 respectively. The local variety had 14.58% termite attack in 2008 while 95/19127 had 12.64% in 2009. The local variety had highest beetle attack 45.83% and 32.76% in 2008 and 2009 respectively. The least prone to termite and beetle attack was recorded in TDr 75/1/2, 2.72 and 8.15% respectively in 2008 and 2.99 and 6.59% in 2009 respectively. The study suggested that TDr 75/1/2 and 95/18894 should incorporate in the farming system of the study area due to their high yielding capacity and resistance to pest attack at harvest.

Hongos asociados a la pudrición seca de tubérculos de ñame (Dioscorea rotundata Poir.) en Córdoba, Colombia

Introducción. La pudrición seca es una enfermedad que ha adquirido gran importancia en Colombia debido a que ocasiona la pérdida de los tubérculos del ñame (Dioscorea rotundata Poir.), tanto en campo como en almacenamiento, afecta los ingresos económicos y la productividad de los pequeños productores. Es escasa la información respecto a los agentes causales de esta enfermedad, por lo que no se tienen claras las estrategias para el manejo de esta problemática. Objetivo. Identificar y caracterizar hongos asociados a la pudrición seca de tubérculos de ñame. Materiales y métodos. Esta investigación se realizó entre marzo y octubre del año 2019, en la zona costanera del departamento de Córdoba en el Caribe colombiano. Se colectaron tubérculos de ñame en almacenamiento, debido a que los agricultores los conservan como semillas para próximas cosechas. En laboratorio se aislaron de las lesiones los hongos asociados, se caracterizaron y luego se identificaron a través de la amplificación de la región ITS (Internal Transcribed Spacer) del DNA ribosomal. Resultados. Se aislaron veintiocho crecimientos fúngicos asociados a la pudrición seca de los tubérculos del ñame, los cuales se agruparon en once morfotipos, de los cuales se identificaron diez especies, pertenecientes a nueve géneros fúngicos. Conclusión. Seis hongos podrían estar asociados a la pudrición seca de los tubérculos de ñame en la zona costanera de Colombia. Estos serían: Lasiodiplodia theobromae, Fusarium solani, Rhizopus oryzae, Neocosmospora rubicola, Neoscytalidium dimidiatum y Curvularia aeria.