BEKOLO NDONGO

In-vitro effectiveness of aqueous extract of organic compost against Helminthosporium turcicum (cryptogamic disease pathogen of maize)

Daouda Kutnjem, Anne Ayo, Ecclèsiaste Marien Ambombo Onguene, Carole Christèle Egono Ndemé, Bekolo Ndongo, Tofel Haman Katamssadan et 1 autre(s)

International Journal of Agricultural Research Innovation and Technology

Sustainable agriculture requires the application of biofertilizers and biopesticides in farming systems. The aim of the study was to analyze in-vitro the effect of aqueous extracts from organic compost on the development of cryptogamic disease in maize plants for yield improvement. The study was carried out in the laboratory using a pure strain of Helminthosporium turcicum previously isolated from infected maize leaves showing symptoms of the disease. Aqueous substrates of unsterilized and sterilized composts, with the concentrations 0.5, 1.0 and 2.0 mL were respectively mixed with liquid PDA at 19.5; 19 and 18 mL for a final volume of 20 ml, then aseptically poured into 90 mm diameter Petri dishes under the laminar flow hood. After solidification, 7 mm-diameter mycelial discs from young H. turcicum cultures were deposited on the agar pellets. 48 hours after incubation, mycelial growth was measured 4 times until the positive control Petri dish was invaded by mycelial filaments. The results showed that the mycelial growth of the H. turcicum strain in the presence of the sterilized aqueous compost extract was significantly reduced. Increasing the concentration significantly inhibited strain growth to the order of 95.89% at a concentration of 2 mL sterilized aqueous compost extract. Similarly, in the presence of the unsterilized aqueous compost extract, the mycelial growth of H. turcicum was also reduced. The Increasing concentration inhibited the pathogen growth by up to 76.92%, at the concentration of 2 mL. These results showed that the aqueous extract of organic compost contains compounds that could be responsible for producing suppressive substances accountable for the mechanisms inhibiting the mycelial growth of H. turcicum. Int. J. Agril. Res. Innov. Tech. 14(2): 62-73, December 2024

• #plant disease management techniques
• #nematode management and characterization studies
• #composting and vermicomposting techniques
• #compost

Soursop (Annona muricata L.) seed extracts: phytochemical composition and biocontrol potential against cercosporiosis in okra (Abelmoschus esculentus L. Moech)

Hubert Bolie, Libert Brice Tonfack, Sylvère Landry Lontsi Dida, Patrice Zemko Ngatsi, Juste Philantrope Abega, Eric Bilo’a Ndongo et 3 autre(s)

Investigational Medicinal Chemistry and Pharmacology

Background: Annona muricata, or soursop, is a tropical plant known for antimicrobial and antiparasitic properties, widely used in traditional remedies. Extracts from leaves, seeds, and bark show activity against pathogens in humans and plants, making it a promising candidate for natural biopesticide development as safer alternatives to chemical controls. This study evaluates Annona muricata seed extracts as bio-fungicides against Cercospora leaf spot in okra under field conditions. Methods: Capillary gas chromatography and mass spectrometry (GC-MS) analyzed aqueous and organic (acetone, ethyl acetate, and methanol) extracts. Two okra varieties (V1 and V2) were tested in field trials during 2019 and 2020. Six treatments included control, synthetic fungicide (3.33 g/L), aqueous extract (33.33 g/L), and methanol, acetone, and ethyl acetate extracts (1:600 v/v). Disease incidence, severity, and yield were measured. Results: GC-MS identified eight antifungal compounds (hexadecanoic acid methyl ester, hexadecanoic acid ethyl ester, hexadecane, n-hexadecanoic acid, octadecanoic acid methyl ester, 9-octadecanoic acid ethyl ester, and 10-octadecadienoic acid (Z,Z)-methyl ester), though these were not directly tested in this study. The Cercospora incidence at 12 weeks after sowing was significantly reduced from 51.11 % and 47.82 % in control plots during 2019 and 2020, respectively, to 8.88 % and 6.64 % in plots treated with aqueous extract and 9.99 % and 9.76 % in plots treated with methanol extract. Yields were highest with aqueous extract (6.48 and 5.22 t/ha), outperforming methanol extract, synthetic fungicide, and control. Conclusion: Bio-fungicides from Annona muricata extracts offer environmentally friendly options for managing okra cercosporiosis

• #agricultural practices and plant genetics
• #insect pest control strategies
• #agricultural pest management studies
• #abelmoschus

Bio-effectiveness of Balanites aegyptiaca (L.) Del. seed extracts against Colletotrichum capsici (Syd.) Butler & Bisby causal agent of anthracnose in cowpeas (Vigna unguiculata (L.) Walps.) under natural conditions

Tize Tize, Patrice Zemko Ngatsi, Sylvère Landry Lontsi Dida, Apollinaire Njome Toka, Thierry Songwe Atindo, Eric Biyo’a Ndongo et 2 autre(s)

Innovations in Agriculture

Anthracnose disease is one of the major causes of yield losses around 45 to 85% in cowpea crops production in Cameroon. Synthetic fungicides are commonly used for diseases management, yet concerns exist regarding their cost effectiveness and environmental impact. This study aimed to control the development of cowpea anthracnose by using extracts from the seeds of Balanites aegyptiaca (L.) Del. The experimental design was a “split-plot” with four replicates. The varieties constituting the main plots randomly in replication with two variants: V1 (Tiligré) and V2 (Lori 24-130) and treatments represented sub-plots randomized within the main plot (T0: control; T-AqE: aqueous extract; T-AcE: acetone extract; T-ME: methanol extract; T-Fong: synthetic fungicide containing 80% of maneb) during two campaigns (2020 and 2021). As results, the plots treated with synthetic fungicide T-F: (9.78 and 9.1%), aqueous extracts (10.6 and 20.48%) and acetone extracts (12.2 and 12.3%) recorded lower severity than control plots (64.14 and 59.82%) for varieties V1 and V2, respectively. The yields were higher in plots treated with aqueous extract (794.05 and 926.63 kg ha -1 ) and lower in the control plots (518.03 and 545.055 kg ha -1 ) respectively for the varieties V1 and V2. Balanites aegyptiaca (L.) seed extracts could be used in the integrated control of cowpea anthracnose disease.

• #agricultural pest management studies
• #botanical research and chemistry
• #plant growth and agriculture techniques
• #colletotrichum capsici

Response of cassava (Manihot esculenta Crantz) genotypes to natural infestation by scale insect pest Stictococcus vayssierei Richard (Hemiptera: Stictococcidae)

Patrice Zemko Ngatsi, Bekolo Ndongo, Zachée Ambang, Pierre Eke, William Norbert Tueguem Kuate, Sylvère Landry Lontsi Dida et 2 autre(s)

Current Research in Insect Science

Cassava is mostly grown for its starchy roots, which ensure food security. However, it is heavily attacked by the African root and tuber scale (ARTS) Stictococcus vayssierei in Central Africa. This pest is a severe constraint to the production of cassava, food and income security for smallholder farmers. Crop resistance development through the selection of varieties with resistant traits against targeted pests is a promising approach to pest control. This study investigated cassava genotypes' response to natural infestation and determined their resistance levels against S. vayssierei. Six cassava genotypes (two local and four improved) were planted in a completely randomized block design with four replicates. Agronomic parameters and ARTS density were evaluated at 3, 6, 9 and 12 months after planting (MAP). Biochemical content was determined on the pith and cortex of 12 MAP aged tuberous roots. As a result, the improved Excel variety recorded the highest scale density per plant with 102.83±4.14 ARTS/P at 9 MAP. At 12 MAP, high activity of total cyanide (69.18±0.88 and 69.16±1.44 mg/kg) and phenylalanine ammonia-lyase (0.142±0.020 and 0.145±0.010 ΔA/min/mg) were observed in the cortex of the tuberous roots of the improved varieties TMS 96/0023 and TMS 92/0057 which were colonized by the lowest ARTS density. The local variety (Douma) had a high content of total phenols (44.87±1.15 µg/g) in the pith. It also produced the highest yield (23.8±2.9 t ha-1). Varieties TMS 96/0023, TMS 92/0057 and Douma may be the most suitable varieties for the control of ARTS stress.

• #cassava research and cyanide
• #plant micronutrient interactions and effects
• #agricultural pest management studies
• #pest analysis

The Efficacy of Crinum Zeylanicum L. Leaf Extract Analysis by GC-MS in Inhibiting Mycelial Growth of Sclerotinia Sclerotiorum Isolates on Common Bean (Phaseolus Vulgaris L.)

Claire Stéphane Tsogo, Patrice Zemko Ngatsi, Nobert William Tueguem Kuate, Marie Elvia Akong, Thierry Songwe Atindo, Hubert Boli et 2 autre(s)

International Journal of Agriculture & Environmental Science

• #plant tissue culture and regeneration
• #plant pathogens and resistance mechanisms
• #botanical research and chemistry
• #sclerotinia sclerotiorum

Efficacy of Aqueous Extract of the Seeds of Annona muricata L. in the Control of Late Blight (Phytophthora infestans) of Tomato (Lycopersicon esculentum Mill.) in the Field

Ramsès Tsala, Patrice Zemko Ngatsi, Nono Carine Temegne, Sylvere Landry Dida Lontsi, William Norbert Kuaté Tueguem, Abdou Nourou Koné Nsangou et 1 autre(s)

Journal of Modern Agriculture and Biotechnology

Objective: An experiment was conducted to propose an agroecological alternative to synthetic fungicides for the control of late blight of tomato in field. The aim of this study was to evaluate the effect of aqueous extract of Annona muricata seeds (AqEAM) against late blight and yield parameters of tomato. Methods: Two varieties (Rio Grande and Lindo F1) constituting the main plots and three treatments (aqueous extract of A. muricata, synthetic fungicide Mancozeb 800g/kg and control) represented sub-plots were used in a split-plot design with four replicates. The treatments were applied two weeks after transplanting and the dose of AqEAM used was 70g/L. Incidence, severity of late blight and agronomic parameters were evaluated. Results: The results show that the application of AqEAM significantly reduced the incidence of late blight in the field by 55.84% and the severity by 80.35% compared to the control at 76 days after transplanting (DAT). Furthermore, no significant differences were observed between AqEAM and the synthetic fungicide on the incidence and severity of late blight. In terms of yield (t ha-1), tomatoes treated with AqEAM showed a significant increase of 26.14% and 25.7% respectively compared to the control and the synthetic fungicide. The Lindo F1 variety yielded best (10.80t ha-1) than Rio Grande variety (6.60t ha-1). Conclusion: These results suggest that aqueous seeds extract of Annona muricata is effective as the synthetic fungicide and would therefore be recommended as an alternative in biological control of late blight of tomato.

• #plant pathogens and resistance
• #plant pathogens and fungal diseases
• #agriculture, plant science, crop management
• #annona muricata

Chemical characterization and insecticidal effect of <i>Moringa oleifera</i> L. seeds extracts on common bean weevil (<i>Acanthoscelides obtectus</i> Say)

Thierry Atindo Songwe, Bekolo Ndongo, William Norbert Kuaté Tueguem, Désiré Manga Anaba, Patrice Zemko Ngatsi, Mustafa Abdullah Yılmaz et 3 autre(s)

Natural Resources for Human Health

Some insects cause high losses of the common bean during storage, namely, <i>Acanthoscelides obtectus</i> Say. Chemical insecticides are commonly used to control insects, but their overuse adversely affects the environment and consumers' health. There is, therefore, the need for an alternative control method. This study was aimed to evaluate the chemical characterization and insecticidal property of <i>Moringa oleifera</i> seed extract on the developmental stages of <i>A. obtectus</i> in stored beans. Three types of <i>M. oleifera</i> seed extracts, namely methanol, ethanol and acetone extracts, were used at doses of 12.5, 25 and 50 µl/ml each. HPLC-MS was used to characterize these extracts. The toxicity of extracts against the adults, the number of eggs and the viability rate of laid or emerged eggs of <i>A. obtectus</i> were evaluated. The results show that <i>M. oleifera</i> seed extract is rich in Hesperidin, Quinic acid, gallic acid, protocatechuic acid, 4-OH benzoic acid, cynaroside, isoquercitrin, cosmosiin, quercitrin, luteolin, naringenin, salicylic acid, Apigenin and Fumaric acid. The acetone extract, from day 2, showed a 100% mortality rate in all doses compared to about only 14% in the control treatment. The number of eggs laid in control (236.67) was higher than the null (0) in acetone treatment at 50 µl/ml. M. oleifera seed extracts contain chemical molecules. They significantly reduced the damage caused by <i>A. obtectus</i> on stored <i>P. vulgaris</i> grains. Therefore, they can be used as an alternative to chemicals for the protection of stored foodstuffs.

• #moringa oleifera research and applications
• #insect pest control strategies
• #agricultural pest management studies
• #moringa

Effect of pesticides on microbial diversity on agricultural soil in the locality of Akonolinga in the Centre Region - Cameroon

Manga Anaba Désiré, Anaba Manga Jacques Denis, Ngono Ambassa Véronique, Kuate Tueguem William Norbert, Bekolo Ndongo, Biye Elvire Hortense

Magna Scientia Advanced Research and Reviews

Bacteria and fungi constitute microorganisms which provide essential services to the soil ecosystem, not only for the maintenance of its fertility, but also for the degradation of certain pollutants. The present study was carried out to evaluate the effects of a synthetic fungicide and seed extracts of two fungicidal plants (Anonidium mannii and Ricinus communis) on microorganisms in an agricultural soil sample. With the solvents acetone, water and methanol, seed extracts of A. mannii and R. communis were used for phytochemical screening and for the preparation of solutions with concentrations of 50 µl/ml corresponding to fungistatic doses. For microbial colony enumeration, 10-1 dilutions for fungi and 10-2 dilutions for bacteria were spread on the surface of SCA medium supplemented with recommended doses of the chemical fungicide and 50 µl/ml concentrations of A. mannii and R. communis seed extracts. Petri dishes containing these mixtures are incubated with bacteria at 30°C for 24 hours and with the fungi for 7 days. At the end of each period, the types of microorganisms are differentiated by the colours of the colonies formed. For doses recommended for farmers, the chemical fungicide Monchamp 720WP destroys all bacterial and fungal life on solid SCA agar. In extracts containing abundant alkaloids, bacterial colony counts are low while in extracts containing metabolites, bacterial colonies are high. Different groups of fungi were differentiated by the coloration of the colonies formed. A significant number of fungal colonies of different colours were observed in the presence of extracts containing alkaloids and sterols/triterpenes. Microbial diversity will reduce the bactericidal and fungal activity of the plant extracts used and will favour their multiplication in the media. The inability of these plant extracts to destroy microorganisms continues to provide beneficial ecologically services to the ecosystem which ensures soil fertility and environmental preservation. Thus, the use of these plant extracts ensures good environmentally agriculture

• #plant pathogens and fungal diseases
• #plant and fungal interactions
• #plant pathogens and resistance
• #fungicide

Effectiveness of Anonidium mannii seed extracts against Colletotrichum lindemuthianum and Fusarium solani, agents responsible for anthracnose and fusariose of common beans (Phaseolus vulgaris L.) in the Centre region-Cameroon

Manga Anaba Désiré, Bekolo Ndongo, Biye Elvire Hortense, Kuate Tueguem William Norbert, Ngatsi Zemko Patrice, Ngono Ambassa Véronique

International Journal of Current Research in Biosciences and Plant Biology

Anthracnose and Fusariose of beans caused by Colletotrichum lindemuthianum and Fusarium solani respectively are two dreaded diseases that can lead to yield losses of 30 to 100% in the field. The present study was carried out to evaluate the antifungal activities of seed extracts of Anonidium mannii (Annonaceae) on the in vitro growth of C. lindemuthianum and F. solani. Extracts of A. mannii seeds obtained from acetone, water and methanol solvents, were used for phytochemical screening and for the preparation of solutions with concentrations of 12.5, 25 and 50 µl/ml. To evaluate radial growth, explants of 0.7 cm diameter each were obtained from two strains of C. lindemuthianum and two strains of F. solani. They were placed each at the centre of sterile Petri dishes containing the PDA medium supplemented with the different concentrations of extracts and incubated at 23°C for 6 days. The results of the phytochemical screening revealed the presence of alkaloids, phenols, saponins in the A. mannii seed extracts and this depended on the solvent used. The minimum inhibitory concentrations (MIC50 and MIC90) were also calculated. At a concentration of 50µl/ml each, acetone extract inhibited the growth of strain 2 of C. lindemuthianum (2.33 cm) more than the methanol extract (3.26 cm) in six days of incubation. Similarly, the growth of strain 2 of F. solani was strongly inhibited by methanol extract (1.98 cm). The MIC50 of the aqueous extract gave 27.38 µl/ml with F. solani and 32.24 µl/ml for the acetone extract with C. lindemuthianum. Due to their antifungal power, after purification with bioactive compounds, the aqueous, acetone and methanol extracts revealed by the phytochemical screening could be used as synthetic fungicides for the control of anthracnose and fusariose of common bean.

• #plant pathogens and fungal diseases
• #plant pathogens and resistance mechanisms
• #seed and plant biochemistry
• #colletotrichum lindemuthianum

Insecticidal activity of formulations based on Moringa Oleifera seeds on Acanthoscelides Obtectus (Coléoptera: Bruchidae)

Kone Nsangou Abdou Nourou, Alain Heu, Mboussi Serge Bertrand, Manga Essouma François, Mvondo Nganti Dorothée, Ndogho Pégalepo Angèle et 3 autre(s)

International journal of innovation and applied studies

Stored seeds of Phaseolus vulgaris L. in are the target of several insects like Acanthoscelides obtectus Say. These pests can cause losses greater than 80 % after six to seven months of storage. The present study aimed to evaluate the insecticidal effects of Moringa oleifera seeds on adults of A. obtectus in storage through two compositions (ie powdery and oily). Four concentrations of oils (3.33; 6.66; 9.99 and 13.33 μl/g), four powder concentrations (4; 16.67; 33.33 and 50 %) and one negative control (C0 = 0 μL / mL) for each composition were used. The experiment was conducted in the laboratory, with four repetitions. The results of the oil contact toxicity test revealed 100 % mortality at doses of 300 and 400 μL after two days of exposure. As for Moringa powder, the insecticidal effect was less pronounced for all doses with a mortality rate of 55 % at day 5 for doses 10 and 15 g. The inhibition of eggs laid and their viability is a function of the concentration of Moringa oil. On the other hand, the powder had no effect on the number of eggs laid and rather stimulated the viability of the eggs. Moringa oil prevents weight loss of stored bean seeds with a null loss percentage at doses of 300 and 400 μL. As for the powder, it had no effect on the weight loss of bean seeds in storage. The powder and oil of Moringa seeds did not affect the germination capacity of the seeds for all the doses tested. Moringa seed oil can therefore be exploited in the integrated control of the pest of common bean seeds in storage.

• #moringa oleifera research and applications
• #insect pest control strategies
• #moringa
• #biology

Effectiveness of Moringa oleifera (Lam) Extracts against Sclerotinia sclerotorium (Lib) De Bary, the Causative Agent of White Mold of Common Bean (Phaseolus vulgaris L.)

Atindo Songwe Thierry, Bekolo Ndongo, Kuate Tueguem William Norbert, Ngatsi Zemko Patrice, Manga Anaba Désiré, Mossebo Dominique Claude

International Journal of Current Microbiology and Applied Sciences

Common bean (Phaseolus vulgaris L.) plays an important role in human and animal nutrition. However, its cultivation in Cameroon is affected by diseases, especially the white bean mold caused by Sclerotinia sclerotiorum. Methods of protection against this pathogen are the use of chemical fungicides which are very expensive and degrade the environment. The search for alternative solutions is necessary. The objective of this work is to evaluate the antifungal activity of aqueous and organic extracts of Moringa oleifera seeds on the development of two strains of S. sclerotiorum. The experiment was conducted in the laboratory using the Potato Dextrose Agar culture medium and three doses of extracts from organic solvent (methanol, ethanol and acetone) and water extracts were used. These doses were 12.5 (C1); 25 (C2) and 50 (C3) µl/ml. The results showed that, at the highest concentration of 50 (C3) µl/ml, methanol, aqueous, acetone and ethanol extracts of M. oleifera showed a percentage inhibition of 52.56; 60; 97.18 and 100 % respectively for strain 1, and 45.13; 13.85; 56.02 and 97.44 % respectively for strain 2. No significant difference (P Ë‚ 0.05) was observed between the percentages inhibition of extracts with ethanol and acetone for strain 1 (100 and 97.18% respectively) and that obtained with the synthetic fungicide Plantineb 80WP (100%). Minimal inhibitory concentration which reduced growth up to 50% ranged from 0.87 to 1.70 μl/ml ethanolic extract of M. oleifera for strains 1 and 2 respectively compared to 2 and 11.13 μl/ml aqueous extract respectively. The percentage inhibition of growth of strains in C3 dose showed that aqueous and organic extracts of M. oleifera seeds compared to synthetic fungicide can be an alternative control method of S. sclerotiorum.

• #moringa oleifera research and applications
• #plant pathogens and resistance mechanisms
• #essential oils and antimicrobial activity
• #sclerotinia sclerotiorum

Effet du Round-up dans le désherbage de l’arachide (Arachis hypogaea L.) en pré-levée:

Y.M. Tientcheu Tongue, Bekolo Ndongo, Patrice Zemko Ngatsi

Journal de la Recherche Scientifique de l’Université de Lomé

Les mauvaises herbes constituent l’une des principales causes de la baisse de rendement de l’arachide (Arachis hypogaea L.). Elles diminuent ainsi dans les foyers a revenus moyens, la disponibilite de cet aliment de base qui est une importante source en proteines et en matieres grasses. Les mauvaises herbes constituent donc une contrainte majeure pour la securite alimentaire. La presente etude a ete initiee en vue d’apprecier l’influence du RoundUp utilise en prelevee, pour le desherbage de l’arachide. Pour ce faire, deux varietes d’arachides locales, dont une en provenance de Yaounde et une autre en provenance de Bafia au Cameroun ont ete testees en champ dans la localite d’Akonolinga dans la region du Centre. Trois traitements ont ete utilises dans un dispositif en splitplot avec trois repetitions. Les densites moyennes des mauvaises herbes, le nombre de nodules et le rendement ont ete evalues jusqu’a 90 jours. Les resultats ont montre que le nombre de nodules dans le desherbage manuel avec 133,37 ± 7,92 nodules et le traitement chimique T2 avec 120,88 ± 11,01 nodules ont ete significativement (P < 0,05) differents du temoin T0 (35,75 ± 4,59 nodules). En ce qui concerne le rendement, aucune difference significative n’a ete relevee entre le desherbage au RoundUp (659,86 ± 115,85b kg/ha) et le desherbage manuel (769,58 ± 68,80b kg/ha). Les mauvaises herbes les plus abondantes etaient Sida corymbosa represente 1072 fois, suivie de Chromolaena odorata represente 260 fois et Commelina benghalensis, 249 fois. Les parcelles non desherbees etaient les plus infestees par les mauvaises herbes, suivies des parcelles desherbees chimiquement. A cet effet le RoundUp pourrait etre recommande aux agriculteurs afin de soulager la penibilite du desherbage manuel de l’arachide.ABSTRACTWeeds are one of the main causes of reduced yields of groundnuts (Arachis hypogaea L.). They reduce the availability of this staple food, which is an important source of protein and fat, in middle-income households. Weeds are therefore a major constraint to food security. The present study was initiated to assess the influence of Round-Up weed control on groundnuts. To this end, two local groundnut varieties, one from Yaounde and one from Bafia in Cameroon were tested in the field in Akonolinga locality in the Central Region. Three treatments were used in a split-plot design with three replicates. Mean weed densities, number of nodules and yield were evaluated up to 90 days. Results showed that the number of nodule in the hand weeding with 133.37±7.92 nodules and the T2 Round-Up treatment with 120.88±11.01 nodules were significantly (P < 0.05) different from the T0 unweeded (35.75±4.59 nodules). No significant difference in yield was found between Round-Up weeding (659.86±115.85b kg/ha) and hand weeding (769.58±68.80b kg/ha). The most abundant weeds were Sida corymbosa represented 1072 times, followed by Chromolaena odorata represented 260 times and Commelina benghalensis represented 249 times. Unweeded plots were the most infested with weeds, followed by chemically weeded plots. For this purpose, Round-Up could be recommended to farmers in order to relieve the hardship of manual weeding of groundnuts.

• #agriculture and rural development research
• #agricultural pest management studies
• #peanut plant research studies
• #forestry

Résistance à la mosaïque virale de Manihot glaziovii par greffage sur M. esculenta

Zachée Ambang, A. Akoa, Bekolo Ndongo, J. Nantia, Godwill M Chewachong

Tropicultura

Summary Resistance to Mosaic Virus Disease of Manihot glaziovii by Grafting on M. esculenta African cassava mosaic virus (ACMV) is an epidemic disease that causes great yield losses (> 50%). The grafting in the field of M. glaziovii on 3 cultivars of M. esculenta (Alot- Bikon, IITA 8034 and IITA 8061), permitted to evaluate the number of leaves per plant and the evolution of ACMV four times at one month intervals starting from 30 days after planting and the tuber yield, which was determined after 11 months. Crown grafting was realised 100 days after cuttings were planted. Controls consisted of ungrafted plants of each cultivar. After four months development, average number of leaves on the scion and controls varied from 41.3-50.0 and 24.2-45.3 leaves per plant respectively, showing a significant difference (P< 0.05) between grafted plants and controls. ACMV severity (expressed as %: cf. Material and methods) on controls was 54.3 ± 1.4, 51.6 ± 1.4 and 24.1 ± 0.9%, respectively for Alot-Bikon, IITA 8034 and IITA 8061. Meanwhile on grafted treatments, the severity was 9.4 ± 0.6; 7.8 ± 0.6 and 3.1 ± 0.6%, respectively. The use

• #plant virus research studies
• #plant tissue culture and regeneration
• #plant disease management techniques
• #manihot esculenta

Resistance to mosaic virus disease of Manihot glaziovii by grafting on M. esculenta.

Zachée Ambang, A. Amougou, Bekolo Ndongo, J. Nantia, Godwill M Chewachong

Tropicultura

• #plant virus research studies
• #plant disease management techniques
• #plant physiology and cultivation studies
• #manihot esculenta

Vigour and behaviour of fifteen citrus varieties against tristeza in the forest zone of Cameroon

Bekolo Ndongo, Zachée Ambang, BM Louis, Nmj Baptiste, Ysb. Ongono

AFRICAN JOURNAL OF BIOTECHNOLOGY

Fifteen varieties or combinations of citrus (lime, grapefruit, lemons, oranges, mandarin and hybrids) were characterized in the forest zone of Cameroon. Characterization was carried out based on the behaviour of these citrus varieties against citrus tristeza virus (CTV). Foliar and cortical symptoms were evaluated. Six years old plants did not show any immune reaction against the disease. Unusual mild symptoms were observed in varieties normally tolerant to the disease, which constitute an indicator of  the presence of a virulent viral complex. Satsuma mandarin, Lisbon lemon, Eureka lemon and in some aspects Tahiti lime showed a satisfactory behaviour for their vigour and reaction against CTV.

• #cocoa and sweet potato agronomy
• #phytoplasmas and hemiptera pathogens
• #plant virus research studies
• #citrus tristeza virus