Yam Rot Research Articles

Molecular Profiling Ecofriendly Trichoderma Biological Control Agent of Yam Tuber Microbial Rot in Northern Nigeria

This research on isolation and identification of yam rot pathogen fungi from North central Nigeria was carried out to investigate some fungal species associated with yam rot using white yams (Dioscorea rotundata) obtained from Adamawa State, Benue State and Plateau State (Jos) Nigeria. Seven fungi species which cause yam rot were isolated during this study, namely: Aspergillus flavus, Aspergillus niger, Penicillium citrinum, Penicillium echinulatum, Penicilum purpurogenum, Trichoderma spp and Trichophyton spp. Trichoderma yunnanense strain RCBBR_GA1 OP8008361 was identified molecularly. Pathogenicity test carried out confirmed these organisms as the pathological agent of the rot. A. niger statistically has the highest frequency of occurrence (100%). The least encountered fungal species were the P. citrinum (16.6%), P. purpurogenum (33.3%) and Trichophyton spp (33.3). Percentage growth inihibition of A. flavus, A. niger, P. citrinum, P. echinulatum, P. purpurogenum, Trichoderma spp and Trichophyton spp was carried out and they showed varying degree of inhibition. However, Trichopyton spp shows the highest growth of inhibition at 96 hours (41.4%) and 120 hours (73.7%). Trichoderma exhibited the highest control of the isolates (80 mm). Trichoderma inhibited mycelia extension growth of A. flavus (25 mm), A. niger (25 mm), P. citrinum (23 mm), P. echinulatum (23 mm), P. purpurogenum (24 mm) and Trichopyton spp (22 mm) at 96 hours. The result shows that Trichoderma was able to inhibit the growth of the pathogenic fungi, which are associated with yam rot. Fungal isolates from yam rot were examined morphologically and microscopically and the nature of rot was varied. It is recommended that enzymes from Trichoderma should be extracted and applied for reduction of microbial rot of yam tubers.

Phylogenetical Identification of Trichoderma species; an Antagonistic Isolate from South-East Geopolitical Zone of Nigeria

The most significant food crops in West Africa are edible yam types (Dioscorea spp.). Farmers have been extremely worried about yam rot brought on by a fungal infection. The objective of the study was to discover environmentally friendly Trichoderma species from yam tubers using a phylogenic technique and to assess their biocontrol capabilities. Thirty samples of both healthy and diseased yam tubers were taken aseptically from farms in the Osisioma Ngwa Local Government Area of Abia State, Nigeria, and sent to the laboratory for microbiological investigation. The samples were analyzed using conventional microbiological techniques, and dual culture assay method was also used to test antagonistic response. Fusarium sp., Aspergillus niger, and Penicillium sp. were the fungi isolated and identified as pathogens, while Trichoderma strains, Trichoderma asperellum (JN004180.1), and Trichorderma koningiopsis (MF5087061) were identified as the isolated biological control agent. A. Niger’s growth was inhibited by the biological antagonist T. asperelleum by 78.6%, Penicillium sp. by 51.2%, and Fusarium sp. by 69.2%, whereas A. Niger’s growth was inhibited by the antagonist fungus T. koningiopsis by 76.6%, Penicillium by 46.1%, and Fusarium by 61.5%. This study demonstrated the ability of two strains of the fungus Trichoderma, Trichoderma asperellum (JN004180.1) and Trichorderma koningiopsis (MF5087061), to biocontrol the common pathogenic fungi that destroy yam in South-Eastern Nigeria and other parts of the world. It is crucial that Nigeria and sub-Saharan Africa commercialize the Trichoderma sp. biological control agent since doing so will make it easily accessible to low-income farmers.

ANTIFUNGAL ACTIVITY OF SELECTED CHEMICAL AGENTS AGAINST PHYTOPATHOGENIC ISOLATED FUNGI SPORES.

Postharvest deterioration has been a major problem associated with yam storage for both famers and traders and it is caused mostly by micro-organisms especially fungi. During the storage of yam, many organisms such as Aspergillus flavus, Aspergillus niger, Penicillium citrinum and Rhizopus stolonifer are often reported to cause rotting of the stored yams. The aim of this research is to find out the antifungal effect of some commonly used anti-dermatophytic agents,(Fluconazole, Terbinafine Hcl, Ketoconazole, Sodium propionate and Griseofulvin) on the above named isolated fungi spores. This was carried out using zone of inhibition, MICs, MFCs, FICs and FFCs to measure the antifungal activities of the test antifungal agents against the isolated phytopathogenic fungi spores. These agents were found to have fungitoxic effects on the test organisms in the order of: Terbinafine Hcl > Fluconazole > Ketoconazole > Sodium propionate > Griseofulvin. This work indicated that the test antifungal agents were able to inhibit the fungi spores that are widely reported to be associated with yams rot when stored. The observation in this study showed that a good and efficient fungicide against the test organisms that are known to cause yam rot during storage can be effectively arrested with combination of these fungicides.

The Anti-Inflammatory and Antioxidant Effects of Methanol Seed Extracts of Sunflower (Helianthus annuus) and Level of Uric Acid in Gout Induced Albino Rats

The study investigated the control Of Yam rot using Chromoleana odourata and Moringa Oleiferia. Spolt yam was inoculated into a prepared culture media after which the growth of the fungi observed were isolated and subculture to get a pure culture. The pure culture was then treated with the extract from Chromoleana Odourata and Moringa Oleiferia. From the treatment given to the isolated fungi (fusarium specie and Aspergillus specie etc.) it was observed that the extract had a significant effect on the growth of the rot fungi. It was based on this that the study recommended that farmers should use bio-fungicide from C.odorata and M.oliefera in the control of yam rot fungi. Keywords: Control of yam rot, growth of rot fungi, chromoleana odourata, moringa oleiferia DOI: 10.7176/JNSR/13-6-03 Publication date: March 31 st 2021

Near-term impact of climate variability on yam rot incidence over a humid tropical region: projections in CORDEX-Africa scenarios

AbstractThe global population is projected to be enormous by the mid-21st century, whereas, most essential crops being sustained by the rain-fed agriculture are threatened by climate change. Therefore, the study investigated the projected near-future effect of rainfall variability on rot incidence and yam production in humid tropical Nigeria. Production data from the Food and Agriculture Organization and the Nigeria National Bureau of Statistics showed the significant increasing trend in the annual yam output. The field survey conducted in 2018 showed that the maximum percentage of rot incidence occurred in July. Climate Research Unit observational rainfall data from 1979 to 2018 showed the nonsignificant trend in the interannual rainfall variability; however, it showed low variability and a significant decreasing trend in the July rainfall. A pathogenicity test on yam samples confirmed rot by fungi, bacteria and nematodes as virulent pathogens, whereas, the nutritional qualities of the rotted yams were indicated. Monthly rainfall and rot incidence showed positive correlation (r = 0.84, significant at 99% from t-test). The positive characteristic impact values indicated that increase (decrease) in the monthly rainfall corresponds to increase (decrease) in the magnitude of monthly percentage rot incidence. Thus, the significantly decreasing rainfall reduced the quantity of rot incidence and consequently increased the annual yam production for the period. Selected CoOrdinated Regional Downscaling EXperiment-Africa models and the ensemble mean showed a good measure of agreement with observational rainfall in the historical experiments. The efficiencies of the bias-corrected outputs in the representative concentration pathway (RCP) 4.5 and 8.5 indicated improved ‘reasonable’ performances. Bias-corrected projections of the July rainfall showed an increasing trend in both the RCPs, which indicate a potential increase in rot incidence and the consequent decline in annual yam production. The findings are imperative in sustaining the global food supply.

Effects of Some Ethno Medicinal Plant Extracts on Botryodiplodia theobromae the Causal Organism of Yam (Dioscorea rotundata Poir) Rot

Post-harvest deterioration and rot caused by diverse microorganisms is the single most important factor militating against yam production in Nigeria. In an approach towards the development of ecofriendly antifungal compound in controlling yam rot, ethanol and aqueous extracts of six commonly available plants: Vernonia amygdalina, Ocimum gratissimum, Azadirachta indica, Cymbopogon citratus, Carica papaya and Citrus sinensis were tested in combination for their synergistic effect against Botryodiplodia theobromae. Four different extract concentrations (2.5%, 5.0%, 7.5% and 10%) were obtained from each extract mixture. Cold solvent extraction method was used for the extraction of plant materials while food poisoning technique was used for in vitro screening of plant extracts against rot inducing fungal organism. Botryodiplodia theobromae was tested to be pathogenic on healthy yam tubers with rot incidence of 80 mm. The synergistic effects of the combined extract varied with the plants combined, solvent of extraction, concentration of extract and test fungi. Ethanol extract showed greater effect in the inhibition of the entire organism than aqueous. All the extract combinations that had Neem as a component did better than other combinations in aqueous extracts. Inhibition of fungal growth was best observed at 7.5% and 10% extract concentrations. The highest inhibitory effect on the test organism (Botryodiplodia theobromae) was by the combination of Neem/Bitter leaf and Orange/Scent leaf, with values of 98.40±0.095% and 94.24±0.583% respectively for aqueous while the highest inhibition for ethanol extract was observed from Scent leaf/Bitter leaf and Pawpaw/Lemon, with values of 99.80±0.000% and 98.83±0.619% respectively these were significantly (P<0.05) better than other combinations. With respect to the synergistic activity between the plants materials combined in this study, all the combinations showed great synergism against the test organisms. This is likely to be a means of achieving pragmatic, effective control and prevention of food spoilage, since the development of new classes of antifungal agents is of paramount importance. The crude aqueous and ethanolic extracts of all the six plant extracts showed potential synergy on organisms responsible for yam rot, hence they are recommended for the control of rot inducing microbial organisms.

Molecular Identification of Fungal Pathogens Associated with Post-harvest Yam Tubers Rot in Mbam et Kim Division (Cameroon) with Emphasis on Penicillium monomenatosum (Frisvad, Filt. & Wicklow) as a First Report

Nowadays, increasingly complains mention tremendous decay of stored yam tubers in the Mbam et Kim Division, the main producing zone of Cameroon. Knowledge of the specific fungi responsible for yam spoilage is paramount for proper preservation by implementing plausible control measures. This study was therefore undertaken to identify the causative fungal agents associated with yam tubers rot in the survey zone. The isolation of suspicious pathogens was performed as per the Koch’s postulates encompassing artificial inoculation, symptoms recording, re-isolation and comparisons-based re-identification. The identity of isolates was later on ascertained by the sequencing of the 5.8S ribosomal DNA gene (ITS1 and ITS2). Overall, seven fungal species: Fusarium solani, Fusarium oxysporum, Aspergillus niger, Penicillium monomenatosum, Rhizopus oryzea, Talaromyces flavovirens and Bionectria cf. ochroleuca were recovered. P. monomenatosum is reported here for the first time as causative agent of yam rot. The obtained results unveil the identity of the devastating fungus threatening yam availability to consumers throughout the year in Cameroon and represent an initial and crucial step toward planning efficient and reliable control measure to counter the yam rot epidemic.

Evaluation of efficacy of false yam (Icacina oliviformis) as surface protectant against rot pathogens of white yam (Dioscora rotundata Poir)

Rots in yam tubers are the dominant cause of postharvest losses. Therefore, studies were con­ducted to identify the rot-causing organisms in yam and to evaluate the efficacy of false yam (Icacina oliviformis) plant extracts as surface protectants in the storage of yam. The experiment was laid out in a completely randomized design (CRD) design with five treatments (fruit, root and leaf extract of false yam, Mancozeb and tap water) replicated three times. Two concen­trations (50% and 100%) of each extract were also tested. Species were identified based on the structural features, the characteristics and properties of the spore and mycelium. A spore suspension of yam rot fungi was sprayed on healthy yam tubers that had been pretreated with the extracts. Results showed that fungi isolated from rotted yams were Aspergillus niger, A. fla­vus and Penicillium sclerotigenum. Leaf extracts (both 50% and 100%) had the highest growth inhibitions on all the three fungi isolated in vitro. Tubers treated with root and leaf extracts of false yam had a decreased tuber rot lengths of 1.80 mm2 and 2.17 mm2, respectively. The leaves and roots of false yam can be used as a surface protectant of yam in place of Mancozeb. Keywords: Icacina oliviformis; Dioscora rotundata; Mancozeb; Pathogenicity; Aspergillus spp.

Absence of Effects of Herbicides Use on Yam Rots: A Case Study in Wulensi, Ghana

Yam farmers in Ghana have, over the years, used herbicides for weed control, particularly glyphosate. Although this has been helpful to them, there are complaints and concerns, among the yam farmers and a section of the public, that the yam tuber rots easily under the use of herbicides. This study, therefore, was set up at the field level to investigate the possibility of herbicides use causing yam rot. Two yam varieties, “laribako” and “olodo”, were grown under the conditions of chemical weed control (use of glyphosate) and manual weed control in three replicate sites in Wulensi in the Nanumba traditional area of northern Ghana. The study revealed that there was no difference in rots between herbicide treated yams and manually weeded yams, but that there was a difference in rots between “laribako” and “olodo” yam varieties. The results also showed that there was no difference in yield between herbicide treated yams and manually weeded yams. Based on the findings, it can be concluded that, there was no difference in yam rot and yield between herbicides treated and manually weeded yams, but “laribako” was more susceptible to rot than “olodo”.

Purification and Characterization of Cellulase from <i>Aspergillus niger</i> Causing Soft Rot of White Yam in Three Environments in Nigeria

Aspergillus niger is abundant in most tropical soils and invariably, on the surface of yam tubers while still attached to the plant and on the root hairs during harvesting or storage. Naturally, the peridermic surface of the tubers function to exclude pathogen but damage caused by accidental incision or cut surface during weeding, insect attack and harvesting provide avenue for the infection. Aspergillus niger isolated from diseased yam in three zones in Nigeria synthesized cellulase which caused soft rot of the yam within nine days of inoculation. Microscopic and molecular analyses revealed two isolates of A. niger, P1 and P2, from different environment produced cellulase enzymes in significantly different proportions. When protein extracts from the infection were subjected to molecular exclusion chromatography, three peaks of absorption (A, B and C) were produced with only the components of peak A showing cellulase activity. Further fractionation of the components of peak A produced two absorption peaks (Aa and Ab) with only component Aa showing Cellulase activity. A. niger isolates, P1 and P2 showed considerable differences in the intensity of cellulase production suggesting that multiple strains of A. niger in the soil of yam-growing environments synthesized cellulase as transcriptional products in different manner underscoring the effect of physico – chemical properties of the soil on infectivity and virulence of the organism during yam rot.

Extraction Methods and Inhibition Studies of Ten Plant Extracts on Nine Yam Rot Pathogenic Microorganisms

Nine microorganisms, comprising of four bacteria, Erwinia carotovora, Pseudomonas aeruginosa, Serratia marcescens, Klebsiella oxytoca and five fungi, Rhizopus stolonifera, Aspergillus niger, Aspergillus flavus, Fusarium oxysporum and Penicillium marneffei, isolated from rotten yam tubers of 2016 harvest year, were treated with ten plants extracts (Passiflora edulis, Daniella oliveri, Ceiba pentandra, Jatropha tanjorensis, Azadrichta indica, Carica papaya, Moringa oleifera, Mangifera indica, Terminalia catapa and Senna alata), singly and synergistically by incorporation of extract in media for inhibition test. Two plant extracts singly and completely inhibited the growth of three organisms: Terminalia catapa at 100% and 10-1 showed complete inhibition (a) of Erwinia carotovora. Passiflora edulis at undiluted (100%) concentration completely inhibited Rhizopus stolonifer and Penicillium marneffei, respectively. Synergistic plant extract recorded complete inhibition (a) of all the four bacteria isolates at 2 mL extract incorporation; ten (10) mL extract incorporation in media recorded complete inhibition (a) of three out of the five fungi isolates: Rhizopus stolonifer, Fusarium oxysporum and Penicillium marneffei, respectively; the other two fungi recorded high inhibition (b) of Aspergillus niger and Aspergillus flavus, respectively. Hot aqueous synergistic plants extract recorded poor inhibition of the isolates as compared to the cold. Soxhlet solvent extracted synergistic plants extract, however, recorded lower inhibition as compared to hot aqueous synergistic plants extract and cold aqueous synergistic plants extracts. Room temperature solvent extracted synergistic plants extracts recorded inhibition that was same as that obtained with cold aqueous synergistic plants extract. This research indicates that heat employed extractions recorded less inhibition activity.

Postharvest Loss Control: Synergistic Plants Extract Inhibition of Ten Microbial Yam Rot Organisms

Nine microorganisms were isolated from four varieties of Dioscorea rotundata (gbongu, ogoja, Amula, Hembamkwase); four bacteria, Erwinia carotovora, Pseudomonas aeruginosa, Serratia marcescens, Klebsiella oxytoca and five fungi, Rhizopus stolonifera, Aspergillus niger, Aspergillus flavus, Fusarium oxysporum, Penicillium marneffei, from five local government areas of Benue State (Vandeikya, Ukum, Katsina Ala, Guma and Logo). Pathogenicity test on the isolates confirmed them to be the cause of rot. The nine plants extract (Ceiba pentandra, Jatropha tanjorensis, Azadirachta indica, Moringa oleifera, Carica papaya, Mangifera indica, Daniella oliveri, Terminalia catapa and Passiflora edulis) synergistically added inhibited all the four bacteria isolates completely. The five fungi were inhibited by 60% (c) - 80% (b); Rhizopus stolonifera, Aspergillus flavus, Fusarium oxysporum; and Aspergillus niger, Penicillium marneffei, respectively.

Evaluation of isolates of Trichoderma, Pseudomonas and Bacillus species as treatment for the control of post-harvest fungal rot disease of yam (Dioscorea spp.)

The efficacy of four biological control agents (BCAs): Trichoderma asperellum strain NGT158, T. longibrachiatum strain NGT167, Bacillus subtilis and Pseudomonas fluorescens for the management of post-harvest tuber rot among four yam species, Dioscorea rotundata, D. cayenensis, D. alata, and D. dumetorum was evaluated. Rotted yam tubers were collected across three agroecological zones in Nigeria to isolate six infecting fungal pathogens: Aspergillus niger, Lasiodiplodia theobromae, Rhizoctonia solani, Penicillium oxalicum, Fusarium oxysporum and Sclerotium rolfsii. The BCAs were isolated by serial dilution and rot inhibition of treated tubers was evaluated using destructive sampling method in vivo after six months of storage. Bacillus subtilis was generally most effective, especially when applied 24 h before the inoculation of test pathogens across the four yam species, with percent inhibition that ranged between 47.8 and 81.2%. However, the four BCAs showed good potential in the control of the fungal pathogens causing post-harvest yam rot.

EFFECT OF FUSARIUM NYGAMAI INFECTION ON THE CHEMICAL COMPOSITION OF FLOUR FROM TWO YAM VARIETIES

Yams (Dioscorea spp) are among the oldest food crops. It is estimated that after six months of storage up to 56% of the crop is lost to rot. In Nigeria, fresh yam tubers are used for production of Elubo (yam flour) for preparation of amala, as it is called among the Yoruba in Western Nigeria, and akwunaji in the east of the River Niger. Many researchershave emphasized the importance of microbial rotting in causing storage losses. This study evaluated the effect of yam rot on the nutritional values of Fusarium infected yam tubers.Tubers from two yam (Dioscorea rotundata Poir.)varieties-Nwopoko and TDr95/19177-were infected with Fusarium nygamai pure culture and stored for 12 weeks, after which the tubers were used to produce yam flour and were analyzed for their nutrient composition comprising: dry matter/ moisture content, ash, total sugar, starch, amylose, vitamin C, protein and tannins. Wholesome yams of the same varieties were also used to produce yam flour and equally evaluated for the same nutrients. Infection with Fusariumnygamai led to a significant reduction (p<0.05) in the nutrient composition of the infected yam flour compared with those ofwholesome samples. Vitamin C content reduced from 41.10 to 27.26 (mg/100g) in variety Nwopoko and 36.30 to 30.53 (mg/100g); in variety TDr95/19177. Corresponding values for protein content was from 5.05 to 4.60% and 4.93 to 4.62%; Ash Content from 1.32 to 1.30% and 1.36 to 1.24%; Total Sugar Content from 5.34 to 5.20% and 5.21 to 5.02%; Starch 78.71 to 77.61 and 89.28 to 81.53%; Amylose from 29.95 to 28.87% and 30.01 to 27.95%. However, an increase in the tannin content – (1.84 and 1.94 mg/g) as against (0.31 and 0.26 mg/g) in Nwopoko and TDr 95/19177 varieties respectively was observed. The increase in the tannin content implies an increase in the antinutrient composition. The tendency to produce Elubo used for preparation of amala with rotten yam (possibly Fusarium infected) should be discouraged.

Effect of Ethanol and Petroleum Ether Extracts of Some Medicinal Plants on Sclerotiumrolfsii, Causal Agent of Postharvest Rot of Yam (Dioscorea Spp.)

Ethanol and Petroleum ether of leaves of Azadirachtaindica A. Juss, Citrus aurantifolia (Christm.)Swingle, Jatrophacurcas L., Anacardiumoccidentale L., seeds of Garcinia kola Heckel and peels of Citrus sinensisOsbek were studied for in vitro activity against mycelial growth and sclerotium germination of Sclerotiumrolfsii, Sacc., the causal agent of postharvest yam rot. The phytochemical screening of the extracts of the medicinal plants revealed the presence of alkaloids, flavonoids, glycosides, steroids, saponins, tannins and terpenoids. The ethanol and petroleum ether extracts showed varying levels of fungitoxicity activity with the ethanol extracts being more effective. Mycelial growth of S. rolfsii was significantly (P < 0.05) reduced by ethanol extracts of C. sinesis (89.63 – 100%), C. aurantifolia (67.04 – 83.28%) and A. indica (53.70 – 69.38%) during the period of incubation. Sclerotium germination was also significantly (P < 0.05) reduced by ethanol extracts of C. sinesis (87.50%), C. aurantifolia (62.50%) and A. indica (50%). This study showed the potentials of extracts of some plant products to control S. rolfsii in yam.

Composition, radical scavenging and antifungal activities of essential oils from 3 Helichrysum species growing in Cameroon against Penicillium oxalicum a yam rot fungi.

The chemical composition of essential oils from leaves of Helichrysumcameroonense Hutch. and Dalziel, Helichrysum cymosum Sensu C. D. Adam, Helichrysum globosum Sch. Bip. ex A. Rich. and flowers of Helichrysumcameroonense was examined by means of GC and GC-MS. In addition, the radical scavenging and antifungal activities were assayed according to the DPPH (Diphenyl Picryl Hydrazyl) and dilution methods respectively. The results showed a predominance of monoterpenes in the oils of the leaves (89.5%) and flowers (62.9%) of H. cameroonense and of sesquiterpenes (58.0%) in that of H. cymosum. Extract from H. globosum was characterized by comparable proportions of monoterpenes (49.6%) and sesqiterpenes (49.1%). The major components were found to be a-pinene (46.4%) and camphor (11.5%) in the oil of leaves of H. cameroonense while a-pinene (31.4%) and guaienol (18.9%) were those from the flowers of the same specie. ∆-3-Carene (16.1%) and b-caryophyllene (12.0%) were the predominant compounds of the essential oils ofH. cymosum and a-pinene (36.6%), valerianone (10.9%) were those of H.globosum. The radical scavenging activities of essential oils from the leaves of H.cameroonense and H. cymosum were found to be 4.9 and 6.3 g/l respectively while butylated hydroxy toluene (BHT) used as reference has a SC50 =7.0 mg/l, On another hand, the essential oils from the leaves of these Helichrysum species showed significant antifungal activities against Penicillium oxalicum, with percent inhibition at 5 mg/ml ranging from 54.7 to 100%. These results highlight the potential of some essential oils as an alternative tool to fight this pathogen which is one of the most prevailing causing agent of soft rot of post harvest yam tuber. Key words: Helichrysum, Asteraceae, essential oil, radical scavenging activity, antifungal activity, Penicillium oxalicum, yams, Discoreaceae.

Evaluation of Some Tropical Enthnomedicinal Plants for Biopesticidal Potentials for the Protection of Yam Biodeterioration

Ten tropical plant species used locally in ethnomedicinal practices were evaluated for their biopesticidal potentialsfor the control of yam biodeterioration in order to use them as substitute for synthetic pesticides in yam (Dioscorearotundata Poir) production to control biodeterioration in storage. Seedyam setts slightly infested with rootknotnematodes (Meloidogyne spp. Goeldi, 1887; Chitwood, 1949) were treated with acetone extract of the plantmaterials by dipping for 24 hours at room temperature (30 ± 2C°). The treated seedyams were assessed after four(4) weeks, six (6) weeks and twelve (12) weeks for the effects of the plant extracts on inhibition of sprouting ofseedyams, inducement of seedyam sprouting and biodeterioration, respectively. After four (4) weeks in storage,Piper guineense treatment appeared to inhibit the sprouting of seedyams (75%) as compared with other treatmentsbut without statistical difference (p70.05). The extract of Anacardium occidentale treatments statistically (p < 0.05)induced seedyam sprouting best (83.3%); followed by Carica papaya (58.3%); Crotolaria retusa (48.10%) in relation toothers, after six (6) weeks. Xylopia aethiopica (100%); Chromolaena odorata (100%); Piper guineense (100%); followed byAzadirachta indica (83.7%) controlled yam rot disease effectively (p < 0.05) after twelve (12) weeks in storage.

Antifungal potentials of &lt;i&gt;Azardirachta indica&lt;/i&gt; and &lt;i&gt;Ocimum grattissimum&lt;/i&gt; leaf extracts in the control of yam rot

The effects of dry and fresh leaf extracts of Azardirachta indica and Ocimum grattissimum on the rot of yam tubers were investigated. Fusarium oxysporium, Botryodiplodia theobromae, Rhizopus stolonifer, Penicilluim notatum and Aspergillus niger were isolated from the rotted yams. Both fresh and dry extracts of the leaves had significant effects on the t pathogens. The dry extracts of O.grattissimum were more effective in checking the growth of the pathogens than the fresh extracts in vivo. Both extracts of A. indica had similar effects on the growths of the pathogens. The also controlled the establishment of the diseases in vivo. Keywords: antifungal, leaf extracts, Azardirachta indica, Ocimum grattissimum, yam rot International Journal of Natural and Applied Sciences Vol. 1(1) 2005: 81-84

Antifungal activity of n-tributyltin acetate against some common yam rot fungi.

The antifungal activity of n-tributyltin acetate (TBTA) was examined in relation to combating yam rot disease. TBTA exhibited a significant effect in vitro and in vivo on four yam rot fungal isolates tested. However, the in vitro toxicity of TBTA was drastically reduced when 2.5% Tween 80 was the solvent instead of 25% acetone, as indicated by the MICs of 156.0 and 5.0 micrograms/ml, respectively.