The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform

Robert Asiedu - One of the best experts on this subject based on the ideXlab platform.

  • Phenotypic analysis of tuber yield- and maturity-related traits in white yam (Dioscorea rotundata)
    AFRICAN JOURNAL OF BIOTECHNOLOGY, 2012
    Co-Authors: Alieu Sartie, Jorge Franco, Robert Asiedu
    Abstract:

    Inadequate yield potential of available varieties and their long growth periods are two of the factors limiting yam ( Dioscorea spp.) production. Identifying yield- and maturity-related traits and breeding for them will enhance production. Ten morphological/physiological traits: time of shoot emergence, time of tuber initiation, plant height, shoot dry weight, time of shoot senescence, tuber fresh weight (tuber yield), tuber number/plant, tuber parenchyma colour, tuber dry matter content and tuber dormancy period were assessed in eight accessions of D. rotundata (white Guinea yam) on the field in 2008 and 2009. Shoot dry weight and plant height were identified as the major tuber yield-related traits. Early field emergence and tuber initiation, short tuber dormancy period and low tuber dry matter content may also be related to tuber yield. High yielding accessions were low in tuber dry matter content. Moreover, early and late maturing accessions could be separated by time of attainment of uniform parenchyma colour within a tuber, length of tuber dormancy period and time of shoot senescence. Accessions were identified that may be used as parents for developing mapping populations for some of the traits assessed in the study. Key words: Dioscorea rotundata , tuber maturity, tuber dormancy, dry matter content, yield related traits, senescence.

  • Yield loss in Guinea yam ( Dioscorea rotundata poir. ) due to infection by Yam mosaic virus (YMV) genus Potyvirus
    Ife Journal of Science, 2012
    Co-Authors: M. O. Adeniji, Robert Asiedu, S. A. Shoyinka, J. D'a. Hughes, T. Ikotun, B. O. Odu
    Abstract:

    An experiment was conducted to investigate the influence of Yam mosaic virus (YMV) genus Potyvirus on the tuber yield of Dioscorea rotundata based on assessment of comparative performance of inoculated and uninoculated plants of two genotypes (TDr 93-31 and TDr 95-127). Symptoms of virus infection were evident on inoculated plants especially at four weeks after inoculation. Visual virus symptom severity scores had significant (P 0.004), harvest index (P < 0.01), leaf chlorophyll content, and intercepted  photosynthetically active radiation (P = 0.01) were obtained from plots with inoculated plants. YMV infection in D. rotundata resulted in a yield loss of 65.4% in TDr 93-31 and 52.6% in TDr 95-127. Reduced capacity for photosynthesis in YMV infected plants, due to increased diffusive resistance of stomata, as well as reduced leaf area and chlorophyll content, contributed significantly (P < 0.001) to their reduced tuber yields. The economic importance of the virus is thus established as it can result in significant loss to resource-poor farmers. Keywords : Dioscorea rotundata , TAS-ELISA, yield loss, Yam mosaic virus (YMV) genus Potyvirus .

  • Flowering intensity in white yam (Dioscorea rotundata)
    The Journal of Agricultural Science, 2009
    Co-Authors: E. I. Hamadina, Peter Craufurd, Robert Asiedu
    Abstract:

    White or Guinea yam (Dioscorea rotundata), grown for its underground tubers, is an important food in West Africa. Progress in yam breeding is constrained by variable flowering behaviour, making hybridization difficult. Yam clones may be dioecious, monoecious or hermaphrodite with variable sex ratios. The proportion of plants that flower and the flowering intensity also vary with season and location. The objective of the present work was to investigate whether variation in flowering behaviour was related to factors determining rate of development (photoperiod and temperature through sowing date, location and year) or growth (cumulative solar radiation and temperature). Sex ratios, the proportion of plants that had flower buds and open flowers, and the number of flowers or spikes was recorded in one male (TDr 131) and one female (TDr 99-9) clone of white yam grown in the field in Nigeria at three locations and at different sowing dates. Clone TDr 131 was uniformly male flowering, while clone TDr 99-9 exhibited a number of sex types with gynoecious, monoecious and trimonoecious plants observed. The proportion of flowering plants was low in both clones, averaging 0·34 in clone TDr 131 and 0·13 in clone TDr 99-9. Day of vine emergence had a significant and contrasting effect on the proportion of flowering plants and on flowering intensity in the two clones. In clone TDr 131, the proportion of flowering plants and flowering intensity declined with later vine emergence at all locations (r=0·43―0·53; P < 0·05), whereas in clone TDr 99-9 the proportion of flowering plants increased with later emergence (r = 0·46, P < 0·01). In clone TDr 131, this response was strongly associated with warmer temperatures (r = 0·49―0·50; P < 0·05) and greater cumulative radiation (r = 0·85―0·93; P < 0.001) between vine emergence and flowering, rather than photoperiod at vine emergence. This suggests that flowering behaviour in the male clone TDr 131 is strongly influenced by factors that affect growth rather than development. Clone TDr 99-9, on the other hand, exhibited no clear relations between flowering and growth or developmental factors, though the proportion of flowering plants and flowering intensity was greatest at planting dates close to the longest day and at temperatures of 25―26 °C. This might suggest that flowering behaviour in clone TDr 99-9 is controlled by photothermal responses.

  • GGE biplot analysis of Dioscorea rotundata cultivar "DENTE" in Ghana
    African Journal of Agricultural Research, 2008
    Co-Authors: Emmanuel Otoo, Robert Asiedu
    Abstract:

    Yield data of 20 genotypes of D. rotundata cultivar “Dente” tested across 15 rain-fed environments during the 2000 to 2004 growing season using Augmented RCBD with 3 blocks were analyzed using the GGE biplot method. The aim of the study was to (i) identify genotypes that combine high yields with stability across environments via GGE (genotype plus genotype x environment) biplot methodology, and (ii) to identify best test environments (representative, discriminating, and unique environments) of improved D. rotundata cvr Dente germplasm in Ghana. The environment (E) explained 36.5% of the total (G + E + GE) variation, whereas G and GEI captured 36.1 and 27.4%, respectively. The first 2 principal components (PC1 and PC2), which were used to create a 2-dimensional GGE-biplot and explained 63.8 and 12.0% of GGE sum of squares (SS), respectively. Genotypes Ge1 and Ge28 were the ideal genotypes (desirable in terms of higher yielding ability and stability). Of the 15 environments tested, biplot analysis identified single mega-environment for all environments. Wenchi (Forest-Savannah Transition) was the most representative and discriminating environment.   Key words: Dioscorea rotundata, GGE-biplot analysis, multi-environment trials.

  • phases of dormancy in yam tubers Dioscorea rotundata
    Annals of Botany, 2006
    Co-Authors: E. I. Ile, Nicholas H. Battey, P Q Craufurd, Robert Asiedu
    Abstract:

    Background and Aims The control of dormancy in yam (Disocorea spp.) tubers is poorly understood and attempts to shorten the long dormant period (i.e. cause tubers to sprout or germinate much earlier) have been unsuccessful. The aim of this study was to identify and define the phases of dormancy in Dioscorea rotundata tubers, and to produce a framework within which dormancy can be more effectively studied. Methods Plants of ‘TDr 131’ derived from tissue culture were grown in a glasshouse simulating temperature and photoperiod at Ibadan (7N), Nigeria to produce tubers. Tubers were sampled on four occasions: 30d before shoot senescence (149 days after planting, DAP), at shoot senescence (179 DAP), and twice during storage at a constant 25 C (269 and 326 DAP). The development of the apical shoot bud was described from tissue sections. In addition, the responsiveness of shoot apical bud development to plant growth regulators (gibberellic acid, 2-chloroethanol and thiourea) applied to excised tuber sections was also examined 6 and 12d after treatment. Key Results and Conclusions Three phases of tuber dormancy are proposed: Phase I, from tuber initiation to the appearance of the tuber germinating meristem; Phase II, from the tuber germinating meristem to initiation of foliar primordium; and Phase III, from foliar primordium to appearance of the shoot bud on the surface of the tuber. Phase I is the longest phase (approx. 220d in ‘TDr 131’), is not affected by PGRs and is proposed to be an endo-dormant phase. Phases II and III are shorter (<70d in total), are influenced by PGRs and environmental conditions, and are therefore endo-/eco-dormant phases. To manipulate dormancy to allow off-season planting and more than one generation per year requires that the duration of Phase I is shortened.

Nora Scarcelli - One of the best experts on this subject based on the ideXlab platform.

E. I. Ile - One of the best experts on this subject based on the ideXlab platform.

  • phases of dormancy in yam tubers Dioscorea rotundata
    Annals of Botany, 2006
    Co-Authors: E. I. Ile, Nicholas H. Battey, P Q Craufurd, Robert Asiedu
    Abstract:

    Background and Aims The control of dormancy in yam (Disocorea spp.) tubers is poorly understood and attempts to shorten the long dormant period (i.e. cause tubers to sprout or germinate much earlier) have been unsuccessful. The aim of this study was to identify and define the phases of dormancy in Dioscorea rotundata tubers, and to produce a framework within which dormancy can be more effectively studied. Methods Plants of ‘TDr 131’ derived from tissue culture were grown in a glasshouse simulating temperature and photoperiod at Ibadan (7N), Nigeria to produce tubers. Tubers were sampled on four occasions: 30d before shoot senescence (149 days after planting, DAP), at shoot senescence (179 DAP), and twice during storage at a constant 25 C (269 and 326 DAP). The development of the apical shoot bud was described from tissue sections. In addition, the responsiveness of shoot apical bud development to plant growth regulators (gibberellic acid, 2-chloroethanol and thiourea) applied to excised tuber sections was also examined 6 and 12d after treatment. Key Results and Conclusions Three phases of tuber dormancy are proposed: Phase I, from tuber initiation to the appearance of the tuber germinating meristem; Phase II, from the tuber germinating meristem to initiation of foliar primordium; and Phase III, from foliar primordium to appearance of the shoot bud on the surface of the tuber. Phase I is the longest phase (approx. 220d in ‘TDr 131’), is not affected by PGRs and is proposed to be an endo-dormant phase. Phases II and III are shorter (<70d in total), are influenced by PGRs and environmental conditions, and are therefore endo-/eco-dormant phases. To manipulate dormancy to allow off-season planting and more than one generation per year requires that the duration of Phase I is shortened.

  • Phases of Dormancy in Yam Tubers (Dioscorea rotundata)
    Annals of botany, 2006
    Co-Authors: E. I. Ile, Peter Craufurd, Nicholas H. Battey, Robert Asiedu
    Abstract:

    Background and Aims The control of dormancy in yam (Disocorea spp.) tubers is poorly understood and attempts to shorten the long dormant period (i.e. cause tubers to sprout or germinate much earlier) have been unsuccessful. The aim of this study was to identify and define the phases of dormancy in Dioscorea rotundata tubers, and to produce a framework within which dormancy can be more effectively studied. Methods Plants of ‘TDr 131’ derived from tissue culture were grown in a glasshouse simulating temperature and photoperiod at Ibadan (7N), Nigeria to produce tubers. Tubers were sampled on four occasions: 30d before shoot senescence (149 days after planting, DAP), at shoot senescence (179 DAP), and twice during storage at a constant 25 C (269 and 326 DAP). The development of the apical shoot bud was described from tissue sections. In addition, the responsiveness of shoot apical bud development to plant growth regulators (gibberellic acid, 2-chloroethanol and thiourea) applied to excised tuber sections was also examined 6 and 12d after treatment. Key Results and Conclusions Three phases of tuber dormancy are proposed: Phase I, from tuber initiation to the appearance of the tuber germinating meristem; Phase II, from the tuber germinating meristem to initiation of foliar primordium; and Phase III, from foliar primordium to appearance of the shoot bud on the surface of the tuber. Phase I is the longest phase (approx. 220d in ‘TDr 131’), is not affected by PGRs and is proposed to be an endo-dormant phase. Phases II and III are shorter (

Asiedu Roberts - One of the best experts on this subject based on the ideXlab platform.

  • Physicochemical and bioactive properties of selected white yam (Dioscorea rotundata) varieties adapted to riverine areas of Nigeria
    African Journal of Food Science, 2014
    Co-Authors: E. Oladeji Alamu, Bussie Maziya-dixon, C. Christian Okonkwo, Asiedu Roberts
    Abstract:

    Yam (Dioscorea spp.) is a major food of cultural, economic and nutritional importance in Nigeria and throughout West Africa. In this sub-region, white yam (Dioscorea rotundata) is the most dominant and important species. This study is aimed at characterizing high yielding yam varieties of this species adapted to riverine areas and forest zones of Nigeria for physical and chemical characteristics. Eleven yam varieties collected from local farmers in the South-southern part of Nigeria were evaluated for their physicochemical characteristics, bioactive compounds (vitamin C, phytic acid and tannin), functional and pasting properties. Results indicated that there were significant varietal differences (P

  • physicochemical and bioactive properties of selected white yam Dioscorea rotundata varieties adapted to riverine areas of nigeria
    Australian Journal of French Studies, 2014
    Co-Authors: Oladeji E Alamu, C. Christian Okonkwo, Bussie Maziyadixon, Asiedu Roberts
    Abstract:

    Yam (Dioscorea spp.) is a major food of cultural, economic and nutritional importance in Nigeria and throughout West Africa. In this sub-region, white yam (Dioscorea rotundata) is the most dominant and important species. This study is aimed at characterizing high yielding yam varieties of this species adapted to riverine areas and forest zones of Nigeria for physical and chemical characteristics. Eleven yam varieties collected from local farmers in the South-southern part of Nigeria were evaluated for their physicochemical characteristics, bioactive compounds (vitamin C, phytic acid and tannin), functional and pasting properties. Results indicated that there were significant varietal differences (P<0.05) among the parameters evaluated. The moisture contents of the investigated varieties ranged from 59.5 to 68.8%, ash content ranged from 1.39 to 2.93%, protein content from 1.96 to 4.90%, fat content from 0.356 to 3.39%, total free sugars from 1.05 to 7.02% and total starch from 33.9 to 75.7%. The bioactive content results show that vitamin C content ranged from 5.64 mg/100 g to 6.99 mg/100 g, phytate from 1.12 to 2.37% and tannin from 0.359 to 1.18 mg/g. The pasting properties results show that peak viscosity ranged from 215 to 470 RVU, trough viscosity from 198 to 385 RVU, breakdown viscosity from 8.71 to 84.5 RVU, final viscosity from 278 to 571 RVU, setback viscosity from 66.2 to 204 RVU; peak time ranged from 4.97 to 7.0 min and the pasting temperature from 61.7 to 62.6°C. This study shows that the physical and chemical characteristics of these high yield yam varieties were similar to those reported for most yam varieties in other parts of Nigeria and has a great potential as source of bioactive compounds and protein. Key words: Yam, Dioscorea rotundata, riverine areas, varieties.

Muluneh Tamiruoli - One of the best experts on this subject based on the ideXlab platform.

  • genome analyses reveal the hybrid origin of the staple crop white guinea yam Dioscorea rotundata
    Proceedings of the National Academy of Sciences of the United States of America, 2020
    Co-Authors: Yu Sugihara, Kwabena Darkwa, Hiroki Yaegashi, Satoshi Natsume, Motoki Shimizu, Akira Abe, Akiko Hirabuchi, Kazue Ito, Kaori Oikawa, Muluneh Tamiruoli
    Abstract:

    White Guinea yam (Dioscorea rotundata) is an important staple tuber crop in West Africa. However, its origin remains unclear. In this study, we resequenced 336 accessions of white Guinea yam and compared them with the sequences of wild Dioscorea species using an improved reference genome sequence of D. rotundata In contrast to a previous study suggesting that D. rotundata originated from a subgroup of Dioscorea praehensilis, our results suggest a hybrid origin of white Guinea yam from crosses between the wild rainforest species D. praehensilis and the savannah-adapted species Dioscorea abyssinica We identified a greater genomic contribution from D. abyssinica in the sex chromosome of Guinea yam and extensive introgression around the SWEETIE gene. Our findings point to a complex domestication scenario for Guinea yam and highlight the importance of wild species as gene donors for improving this crop through molecular breeding.