Tropical root crops : root crops and the African food crisis; proceedings of the Third Triennial Symposium of the International Society for Tropical Root Crops - Africa Branch, held in Owerri, Nigeria 17-23 Aug. 1986

Meeting: International Society for Tropical Root Crops - African Branch, Triennial Symposium, 17-23 Aug. 1986, N

Optimized protocol for in vitro pollen germination in yam (Dioscorea spp.)

Open Access Journal; Published online: 18 Apr 2021Yam (Dioscorea spp.) plants are mostly dioecious and sometimes monoecious. Low, irregular, and asynchronous flowering of the genotypes are critical problems in yam breeding. Selecting suitable pollen parents and preserving yam pollen for future use are potential means of controlling these constraints and optimizing hybridization practice in yam breeding programs. However, implementing such procedures requires a robust protocol for pollen collection and viability testing to monitor pollen quality in the field and in storage. This study, therefore, aimed at optimizing the pollen germination assessment protocol for yam. The standard medium composition was stepwisely modified, the optimal growth condition was tested, and in vivo predictions were made. This study showed that the differences in yam pollen germination percentage are primarily linked to the genotype and growing conditions (i.e., medium viscosity, incubation temperature, and time to use) rather than the medium composition. The inclusion of polyethylene glycol (PEG) in the culture medium caused 67–75% inhibition of germination in D. alata. Although the in vivo fertilization was dependent on female parents, the in vitro germination test predicted the percentage fruit set at 25.2–79.7% and 26.4–59.7% accuracy for D. rotundata and D. alata genotypes, respectively. This study provides a reliable in vitro yam pollen germination protocol to support pollen management and preservation efforts in yam breeding

Optimum time for hand pollination in yam (Dioscorea spp.)

Open Access Journal; Published online: 18 Aug 2022Hand pollination success rate is low in yam (Dioscorea spp.), due partly to suboptimal weather conditions. Thus, determining the most suitable time for pollination could improve the pollination success in yam breeding programs. We performed continuous hand pollination within flowering windows of D. rotundata and D. alata for two consecutive years to determine the most appropriate month, week, and hours of the day allowing maximum pollination success. In D. alata crossing block, we observed significant differences among crossing hours for pollination success (p = 0.003); morning hours (8–12 a.m.) being more conducive than afternoons (12–5 p.m.). No significant differences existed between crossing hours in D. rotundata, though the mid-day seemed optimal. For both species, the time interval 11–12 a.m. was more appropriate for crossing while 4–5 p.m. was the poorest. However, in vitro pollen germination tests showed that mid-day pollen collection (12 noon–2 p.m.) had better results than both extremes, though there were strong genotypic effects on outcomes. Pollination success rates differed significantly among months for D. alata (p 0.05). Differences in pollination success existed across weeks within flowering windows of both D. alata (p < 0.001) and D. rotundata (p = 0.004). The seed production efficiency (SPE) had a similar trend as the pollination success rate. No clear pattern existed between the pollination time and the seed setting rate (SSR) or seed viability (SV), though their dynamics varied with weeks and months. This study provided an insight on the dynamics of pollination outcomes under the influence of pollination times and allows detecting months, weeks, and hours of the day when hybridization activities should be focused for better results

Ethnobotany and Perceptions on the Value of Taro (Colocasia esculenta) among farmers in the Benin Republic

Open Access ArticleTaro (Colocasia esculenta) is a widely grown vegetatively propagated food crop in the Benin Republic. The taro leaf blight (TLB) epidemic in 2009, caused by Phytophthora colocasiae, has destroyed taro production and wiped out many taro landraces in West Africa. A survey was conducted in the southern region of Benin to assess the status of taro and TLB, ethnobotany, farmers' perceptions of taro, and identify production constraints. A structured questionnaire was used to collect information from 24 farmers in 17 villages across six departments, and the TLB incidence was assessed in the same fields. The results revealed the prevalence of TLB across all the villages and a sharp reduction in production since the TLB epidemic. The TLB incidence ranged from 25 to 100%, however, the mean symptom severity score per field assessed on a 1 to 5 rating scale varied between 0.25 and 2.8. Awareness about the TLB or good crop management practices was low. Integrated methods for TLB control and improved agronomic management are crucial to enhance taro yields. In the long term, introducing resistant varieties is critical for the sustainable management of TLB and taro production in Benin

Cassava (Manihot esculenta Crantz) stems quality for root production effectiveness

Four attributes of stem quality: number of nodes1, diameter2, and stem weight3 per 25-cm plantable stake (PS), and the stake position4 were investigated in field trials at Blocks 4, 18 and 24 of the International Institute of Tropical Agriculture (IITA) Onne, Ajibode, Ibadan, Federal College of Agriculture, Akure and Dogodawa, Zaria, Nigeria to evaluate the relationship between good quality cassava planting material and the stem and root yields and to assess the best stake position that gives the best stem and root yields. Forty three cassava mosaic disease resistant varieties were planted during the 2005 and 2008 planting seasons in a randomized complete block design with four replicates while two varieties out of the 43 in trial (TME 7 and TMS 30572) were evaluated in a uniformity trial. The studies found that there is a gradient of number of nodes per stake, weight and diameter in cassava stem from the base to the shoot tip. All cuttings of 25-cm long do not have the same number of nodes (varied from 5-16 nodes), diameter (1.8-3.1 cm) and weight (48-110 g). There was no significant difference (p>0.05) in yield among stakes from the basal, basal-middle, top-middle and top of the stem. The effect of the quality of stakes planted was shown on the percentage missing stands and was 18.2% in research farms, 32.7% (trained personnel farms) and 42.0% (traditional farms). Selection of quality stakes did not have any effect on the yields, but very necessary for improving root yield of cassava