Elsie Hamadina

Dormancy prevents field yams tubers from sprouting, even when environmental conditions are favourable, until 270 days after tuber initiation. A possible role of abscisic acid (ABA) in this regard has been proposed but not established in yam. This study was conducted to assess the role of abscisic acid in the induction of tuber dormancy in D. alata tubers. Rooted minisetts were grown in a hydroponics system containing ABA, a competitive inhibitor of ABA (Fluridone), ABA followed by Fluridone, or non (the control; nutrient solution alone). The four treatments were replicated three times and arranged as Completely Randomized Design. Results show that Fluridone, and ABA + Fluridone treatments induced sprouting on new underground tubers as early as 34 DAT while the new underground tubers from the control, or ABA alone did not sprout even after 120 days in storage. Furthermore, tuber total carotenoid content followed the order Fluridone> control, Fluridone + ABA and ABA alone. Leaf sto...

Changes in crude protein (CP) content of tubers during storage in yam barns can be associated with dormancy and the start of sprouting. Storage environment is known to affect the timing of sprouting, but its effects on changes in crude protein content of yam tubers (during storage and sprouting) is not well understood. This study was conducted to determine the effects of storage environment: natural light (the yam barn) and darkness (created with jute sacs in the yam barn), on CP changes in Dioscorea rotundata Poir. tubers during storage and sprouting. This study was a 2 x 3 factorial experiment, arranged in a Randomised Complete Block design with split-split plots. Tubers of three varieties of yam (Alaako, Dodoro and Odo) were harvested prior to the onset of plant senescence, and stored in the dark and natural light environments. During storage, the tubers were sampled and partitioned into Head, Middle and Tail regions, and then each region into peel and pulp, for CP analysis. Dark...

Rate of germination and the timing of sprouting has been significantly increased and shortened by propagating Allanblanckia seeds obtained from immature fruits rather than seeds from mature fruits. Also, soaking scarified seeds from immature fruits in 10 µM Fluridone for 6 or 12 hr has led to 72% germination in 75 days. Unfortunately, the effect of Fluridone on un-scarified seeds from immature fruits is not known and, the optimum soak duration for inducing the maximum effect on germination is not clear. Therefore, the objective of this study was to determine the effect of 0, 6, 12, 24 and 48 h of soak in 10 µM Fluridone on the timing and percentage germination of mature un-scarified and scarified Allanblanckia seeds extracted from immature fruits. Results showed that scarified seeds commenced germination after a short period (about 50 days after treatment) while germination was delayed in un-scarified seeds (about 100 days after treatment). Rate of germination in scarified seeds was...

This study seeks to determine the effect of tuber age and plant growth regulators (PGRs) on the duration of D. rotundata tuber dormancy. Tubers of D. rotundata var. Tdr 131, generated from pot grown tissue culture plantlets, were harvested at 75 days after planting (DAP) and at 179 DAP. A set of 30 tubers (untreated control) were observed for date of sprouting. Sets of ten tubers were subjected to one of nine treatments: water (treated control), two concentrations each of 2-chloroethanol (CLE), giberrellic acid (GA3) and CLE/thiourea combinations, and one concentration each of thiourea and ethephon at 183, 214, 269 and 331 DAP. The 50th percentile duration from harvest to sprouting ranged from 152 to 166 d in all controls, and 146 to 184 d in the PGR treatments (corresponding to 26 March and 12 May) depending on PGR. Tuber age at PGR application did not affect the duration from harvest to sprouting but the ethylene analogues: 60 ml l-1 CLE +  20 g l-1 thiourea and 1000 mg l -1etheph...

The need to grow more food in the humid tropics to be able feed the ever growing population has resulted in a drastic shortening of the fallow period necessary to maintain soil fertility. This urges the need to develop improved fallow systems, e.g. by using herbaceous legumes as relay cover crops. Herbaceous legumes improve the yield of food crop through weed suppression, N2-fixation, and production of fast decomposing residues that release nutrients to the subsequent crop. In this chapter the results of a field trial are presented in which the residual effects of the herbaceous legume Mucuna pruriens used as a fallow crop on the performance of a subsequent maize crop are studied. Maize grain yields obtained from Mucuna plots were about twice as high as 'those on the control plots, they were about 320 and 180 kg ha"1, respectively, it should be noted that much higher yields could be obtained after the application of 40 kg N ha"1 as urea. Grain yield then amounted to ab...

This study was aimed at estimating pathogenic bacteria in soils under contrasting land-use/land cover types; to determine if the data derived constitute soil quality indicators for assessing soil health status. Soils were sampled from three depths (10 cm, 20cm and 30 cm) from three land-use/land cover types (Forest, Farmlands, and Built-up areas) at each of two study sites (Onne and Choba); and analysed for viable aerobic counts by culturing using the plating method, and the identified pathogenic species were cultured on two types of media (Nutrient Agar and Mac-Conkey Agar) incubated at 37 o C for 72 h for antibiotic sensitivity testing. Data generated were subjected to analysis of variance. Irrespective of land-use/land cover type, soil depths or incubation temperature, Choba soils had higher (P<0.001) viable aerobic counts than Onne soils, but incubating at 37 o C yielded higher counts than 48 o C incubation. More bacteria species were isolated from Onne soils (8 species) than...

Fadama III is a rural development initiative targeting, amongst others, small holder farmers. It is a follow up of previous National Fadama Development Projects, and it is implemented in all but one state of Nigeria. This study covered 5 out of the 8 local counties (known as local government areas, LGAs) of Bayelsa State. This study addressed the social and environmental sustainability of Fadama III projects in the Niger delta, using Bayelsa state as a case study. The study aimed at evaluating the social and environmental status of Fadama III in Bayelsa state, determining compliance with best practices; and suggesting measures to guarantee sustainability. Although there were no detectable adverse effects of the Fadama III sub-projects on the social and environmental settings of the beneficiary localities, there are salient issues that can mar the long-term sustainability of Fadama III. The conceptualization and implementation of rural development programs like Fadama III need improv...

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.

Dormancy is a mechanism that regulates the timing of sprouting (germination) of affected plant parts as well as ensures that the food quality of edible parts is maintained in storage until the following growing season. In yam, however, little is known about the control of tuber ...