Effet de l’Еnrobage des Semences de Maïs (Zea mays L.) avec Trichoderma harzianum sur la Levée et la Croissance des Plantules au Burkina Faso

Au Burkina Faso, de nombreuses espèces de moisissures infectent les grains de maïs entrainant des fontes de semis, des retards de croissance des plantes et la production de mycotoxines dangereuses pour la santé humaine et animale. L’objectif de la présente étude a été d’évaluer le comportement des semences de maïs enrobées avec les conidies d’une souche locale de Trichoderma harzianum ayant présenté des propriétés antifongiques et amélioré la croissance végétative des plantules d’oignon selon des études antérieurs. Six lots de semences de six variétés de maïs ont ainsi été collectés et analysés pour identifier les espèces de moisissures en présence. Les principales espèces identifiées ont ensuite été confrontées in vitro avec T. harzianum pour apprécier l’antagonisme. Des grains de maïs ont enfin été enrobés avec les conidies de T. harzianum en utilisant de l’argile comme liant puis semés et entrenus pendant vingt-cinq (25) jours pour apprécier la levée et la croissance des plantules. Fusarium verticillioides, Aspergillus niger et Aspergillus flavus ont été les trois principaux champignons présents dans les semences analysées à des taux d’infection variant de 8,3 à 89,5%, en fonction des variétés de maïs. L’évaluation de l’antagonisme de T. harzianum a montré une réduction significative de la croissance de ces trois champignons avec des coefficients d’antagonisme compris entre 0,68 et 0,86. Concernant l’effet promoteur de la croissance végétale, l’enrobage des semences avec T. harzianum a permis d’améliorer significativement la levée, la longueur des plantes et des racines ainsi que la biomasse fraiche par rapport aux semences non enrobées.   In Burkina Faso, many mold species infect maize grains causing seedling damping off, plant growth retardation, and the production of mycotoxins which are dangerous for human and animal health. The objective of the present study was to evaluate the behavior of maize seeds coated with the conidia of a local strain of Trichoderma harzianum having shown antifungal properties and improved the vegetative growth of onion seedlings according to previous studies. Six seed lots from six varieties of maize were thus collected and analyzed to identify the existing mold species. The main identified species were then confronted in vitro with T. harzianum to assess the antagonistic effects. Maize seeds were finally coated with the conidia of T. harzianum using clay as binder and then sown and maintained for twenty-five (25) days to assess the emergence and growth of the seedlings. Fusarium verticillioides, Aspergillus niger, and Aspergillus flavus were the three main fungi present in analyzed seeds lots with infection rates varying from 8.3 to 89.5%, depending on the maize varieties. The evaluation of the antagonism of T. harzianum showed a significant reduction in the growth of the three fungal species with antagonism coefficients situated between 0.68 and 0.86. In terms of plant growth-promoting effect, seed coating with T. harzianum significantly improved seedling emergence, plant and root length and fresh biomass, compared to non-coated seeds

L’Enrobage des Semences de Maïs avec Trichoderma harzianum a Amélioré la Levée et la Croissance des Plantes au Burkina Faso

De nombreuses espèces de moisissures infectent les grains de maïs produits au Burkina Faso. La présence de ces champignons sur les grains entraine des fontes de semis, des retards de croissance des plantes et la production de mycotoxines comme les aflatoxines dont la consommation est dangereuse pour la santé humaine et animale. L’objectif de la présente étude a été d’évaluer le comportement de semences de maïs enrobées avec les conidies d’une souche locale de Trichoderma harzianum ayant présenté des propriétés antifongiques et de promotion de la croissance sur l’oignon. Six lots de semences de six variétés de maïs ont ainsi été collectés et analysés pour identifier les espèces de moisissures en présence. Les trois principales espèces identifiées ont ensuite été confrontées in vitro avec T. harzianum pour apprécier l’antagonisme. Des grains de maïs ont enfin été enrobées avec les conidies de T. harzianum puis semés pour apprécier la levée et la croissance des plantules. Fusarium verticillioides, Aspergillus niger et Aspergillus flavus ont été les trois principaux champignons présents dans les semences analysées à des taux d’infection variant de 8,3 à 89,5%, selon les variétés de maïs. L’évaluation de l’antagonisme de T. harzianum a montré une réduction significative de la croissance de ces trois champignons avec des coefficients d’antagonisme compris entre 0,68 et 0,86. Concernant l’effet promoteur de la croissance végétale, l’enrobage des semences avec T. harzianum a permis d’améliorer significativement la levée, la longueur des plantes et des racines ainsi que la biomasse fraiche par rapport aux semences non enrobées.   Many mold species infect maize grains produced in Burkina Faso. The presence of these fungi on the grains leads to seedling damping off, plant growth retardation and the production of mycotoxins such as aflatoxins, the consumption of which is dangerous for human and animal health. The objective of the present study was to evaluate the behavior of maize seeds coated with the conidia of a local strain of Trichoderma harzianum having shown antifungal and plant growth promoting properties on onion. Six seed lots from six varieties of maize were thus collected and analyzed to identify the existing mold species. The three main identified species were then confronted in vitro with T. harzianum to assess the antagonistic effects. Maize seeds were finally coated with the conidia of T. harzianum and then sown to assess emergence and seedling growth. Fusarium verticillioides, Aspergillus niger and Aspergillus flavus were the three main fungi present in analyzed seeds lots with infection rate varying from 8.3 to 89.5%, according to the varieties of maize. The evaluation of the antagonism of T. harzianum showed a significant reduction in the growth of the three fungal species with antagonism coefficients situated between 0.68 and 0.86. In terms of plant growth promoting effect, seed coating with T. harzianum significantly improved seedling emergence, plant and root length and fresh biomass, compared to non-coated seeds

L’Enrobage des Semences de Maïs avec Trichoderma harzianum a Amélioré la Levée et la Croissance des Plantes au Burkina Faso

De nombreuses espèces de moisissures infectent les grains de maïs produits au Burkina Faso. La présence de ces champignons sur les grains entraine des fontes de semis, des retards de croissance des plantes et la production de mycotoxines comme les aflatoxines dont la consommation est dangereuse pour la santé humaine et animale. L’objectif de la présente étude a été d’évaluer le comportement de semences de maïs enrobées avec les conidies d’une souche locale de Trichoderma harzianum ayant présenté des propriétés antifongiques et de promotion de la croissance sur l’oignon. Six lots de semences de six variétés de maïs ont ainsi été collectés et analysés pour identifier les espèces de moisissures en présence. Les trois principales espèces identifiées ont ensuite été confrontées in vitro avec T. harzianum pour apprécier l’antagonisme. Des grains de maïs ont enfin été enrobées avec les conidies de T. harzianum puis semés pour apprécier la levée et la croissance des plantules. Fusarium verticillioides, Aspergillus niger et Aspergillus flavus ont été les trois principaux champignons présents dans les semences analysées à des taux d’infection variant de 8,3 à 89,5%, selon les variétés de maïs. L’évaluation de l’antagonisme de T. harzianum a montré une réduction significative de la croissance de ces trois champignons avec des coefficients d’antagonisme compris entre 0,68 et 0,86. Concernant l’effet promoteur de la croissance végétale, l’enrobage des semences avec T. harzianum a permis d’améliorer significativement la levée, la longueur des plantes et des racines ainsi que la biomasse fraiche par rapport aux semences non enrobées.   Many mold species infect maize grains produced in Burkina Faso. The presence of these fungi on the grains leads to seedling damping off, plant growth retardation and the production of mycotoxins such as aflatoxins, the consumption of which is dangerous for human and animal health. The objective of the present study was to evaluate the behavior of maize seeds coated with the conidia of a local strain of Trichoderma harzianum having shown antifungal and plant growth promoting properties on onion. Six seed lots from six varieties of maize were thus collected and analyzed to identify the existing mold species. The three main identified species were then confronted in vitro with T. harzianum to assess the antagonistic effects. Maize seeds were finally coated with the conidia of T. harzianum and then sown to assess emergence and seedling growth. Fusarium verticillioides, Aspergillus niger and Aspergillus flavus were the three main fungi present in analyzed seeds lots with infection rate varying from 8.3 to 89.5%, according to the varieties of maize. The evaluation of the antagonism of T. harzianum showed a significant reduction in the growth of the three fungal species with antagonism coefficients situated between 0.68 and 0.86. In terms of plant growth promoting effect, seed coating with T. harzianum significantly improved seedling emergence, plant and root length and fresh biomass, compared to non-coated seeds

Susceptibility of fall armyworm Spodoptera frugiperda (JE Smith) to microbial and botanical bioinsecticides and control failure likelihood estimation

peer reviewedDescription of the subject. The fall armyworm Spodoptera frugiperda (JE Smith) has become one of the most devastating pests of maize and other important economic crops in Africa since 2016. Among the alternatives to chemical insecticides, bioinsecticides are an interesting option that needs to be explored. Objectives. The susceptibility of fall armyworm to seven bioinsecticides available on the West African market was evaluated in Burkina Faso. Method. Bioassays were conducted following the approved IRAC 020 protocol. Results. Spinetoram (LC80 = 85.3 µg·l-1) and spinosad (LC80 = 437.9 µg·l-1) were the most toxic at concentrations below those recommended by the manufacturer, and had control failure likelihoods close to 0%. Bacillus thuringiensis and products based on Azadirachta indica and Carapa procera extracts were less effective (at the manufacturers' recommended doses), even though they showed significant levels of toxicity on young instars. Conclusions. A list of effective bioinsecticides should be communicated for sustainable management of fall armyworm in West Africa

Diagnostic, caractérisation et contrôle des maladies fongiques de l'oignon (Allium cepa L.) dans les agrosystèmes maraîchers du Burkina Faso

Onion (Allium Cepa L.) sector plays an important role in the socio-economic development of Burkina Faso. Its production is however confronted with biotic diseases which cause considerable yield losses. A lack of knowledge of the pathogens responsible for these diseases leads to inappropriate use of chemicals, the consequences of which are an unnecessary increase in production costs, important risks of water and crops contamination. The general objective of this study was to develop an integrated onion protection strategy, which application will contribute to improve sustainably, the production levels while preserving the health of producers, consumers, and environment. The achievement of this objective requires, firstly, the realization of a correct and precise diagnosis of the pathogens, the knowledge of the agricultural practices that interact with them and, finally, the development of effective, available and environmentally friendly control methods. Data from the literature reported that the major onion diseases are of fungal origin. Based on this hypothesis, 18 seed samples, 167 whole plant samples and 40 samples of preserved bulbs with various symptoms, were collected in the main basins of vegetable production of Burkina Faso and analyzed between 2013 and 2015 for fungal pathogen occurrence. According to the results of this diagnosis, six main fungal diseases of onion are present in Burkina Faso: Seedling damping-off and basal rot disease caused by Fusarium oxysporum (Schlecht.) Emend. Snyd & Hans and Fusarium solani Sacc. Seedling damping-off and black mold caused by Aspergillus niger Tiegh ; Purple blotch disease caused by Alternaria porri Ellis.; Leaf blight disease caused by Alternaria alternata (Fr.) Keyssler ; Pink rot disease caused by Phoma terrestris Hansen ; White rot disease caused by Sclerotium cepivorum Berk. The last two diseases are located in two zones and the others are present in all visited areas. The identified pathogens are seed-borne and seed-transmitted and the prevalence of Fusarium spp. and Aspergillus spp. was particularly high on locally produced seeds. Basal rot disease appears to be the most damaging because of its direct impact on yields. The disease was identified in the Sourou valley, the largest current onion production area in Burkina Faso. Through a field survey of 250 onion producers in 2015-2016, a review of agricultural practices was carried out in this zone to understand their possible role in the disease epidemiology. The results of this analysis indicate that 35% of producers use local seeds whose poor sanitary quality has also been shown. Almost 80% of producers practice a short rotation between the dry and rainy seasons and 12% practice pure monoculture. These practices do not make it possible to reduce the amount of inoculum of pathogens in the soil. The study reveals an unbalanced fertilization method that favors the use of large amounts of mineral nitrogen at the expense of organic matter. This imbalance could weaken plants and predispose them to attacks by some pathogens. The study concludes at the need to undertake awareness-raising, information and training of producers on the role of agricultural practices in the development of diseases and their management. In this context, three activities aiming at the control of the pathogens detected and transmitted by the seeds were carried out. First of all, botanical extracts of Portulaca oleracea L. and Cymbopogon citratus Stapf. have been tested in seed treatment. These two extracts significantly reduced seed infection rates by Fusarium spp. and Aspergillus niger. However, they negatively affected the germination and growth of seedlings, respectively. Subsenquently, conidial suspensions of the antagonist Trichoderma harzianum were applied to the nursery stage by seed coating and substrates spraying against seedling damping-off caused by F. oxysporum and F. solani. These two practices significantly permitted to significantly improve the emergence and growth of seedlings and protected them against damping-off. Finally, eleven onion varieties available in Burkina Faso were screened for their behavior against basal rot and purple blotch diseases under natural infection conditions in fields. The onion varieties Noflaye and Gandiol + were found to be resistant or tolerant, respectively, to basal rot and more tolerant to purple blotch disease than local varieties. All these results enabled us to develop an integrated protection strategy in 31 components based on the use of a healthy planting material and substrate through the improvement of certain agricultural practices. The strategy also includes necessary accompanying measures as well as the assumptions and risks associated with the use of each component. The implementation of these recommendations requires additional tests to optimize the strategy according to field conditions.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 201

Activité antifongique d’extraits aqueux de Cymbopogon citratus (D.C.) Stapf., Eclipta alba (L.) Hassk. et Portulaca oleracea (L.) contre les principaux champignons transmis par les semences d’oignon (Allium cepa L.) au Burkina Faso

Aspergillus and Fusarium species are the major seed-borne fungi occurring on onion in Burkina Faso according to a previous study. In order to work out effective, available and healthy method of seed treatment against these fungi, this study aimed to evaluate the antifungal activity of three local botanical species. Mycelial growth of Aspergillus niger, Fusarium moniliforme, Fusarium oxysporum and Fusarium solani was evaluated in vitro on media prepared with aqueous extracts of Cymbopogon citratus, Eclipta alba and Portulaca oleracea. The health and germination quality of seeds previously treated with the best aqueous extracts were then evaluated. The aqueous extract of C. citratus significantly inhibited the mycelial growth of all Fusarium species at rates ranged from 42,8 to 92,0% but stimulated the growth of A. niger. Those of P. oleracea inhibited the mycelial growth of all tested fungi at rates ranged from 3,2 to 42,4% while those of E. alba stimulated the mycelial growth of all tested fungi. Seed treatment with the extracts of C. citratus and P. oleracea allowed reducing their infection rates by fungi of over 50%. However, the emergence and growth of seedlings were respectively reduced by P. oleracea and C. citratus compared to those of untreated seeds. Our study concludes that both aqueous extracts have proven antifungal properties. The appropriated shape and dose of use, that does not affect the seedling emergence and growth, should be sought

Identification of seed-borne fungi of onion (Allium cepa L.) in Burkina Faso

This study was carried out to assess the seed-borne fungi of onion in Burkina Faso. Eighteen onion seed samples were collected from local farmers and wholesalers of vegetable seeds in the country and were investigated for fungi. The investigation was done using the “blotter method” on dry seeds and on seedlings. Fungal contamination was detected in all 18 tested samples. Seventeen fungal species belonging to 11 fungal genera were identified in the seed samples: Aspergillus was detected in 17 samples, Fusarium and Rhizopus in 15 samples, Cladosporium in 14 samples and Penicillium in 13 samples. Aspergillus niger and Fusarium oxysporum, known to be the causal agents of black mould and basal rot diseases, were detected in 17 and 11 samples, respectively, by seed analysis and in 10 and 9 samples, respectively, by seedling analysis. The infection rates by the fungal species varied from 0 to 90.3% for A. niger and from 0 to 13.5% for F. oxysporum. Alternaria porri, the causal agent of purple blotch disease was recorded lowly on two seed samples at infection rates of 0,5 and 1%. Exotic seed samples showed better health quality compared to local seed samples. These results indicated that the seeds locally produced by farmers in Burkina Faso are for low health quality and needs strong treatments before use to avoid diseases appearance in fields

Evaluation of the Potential of Trichoderma harzianum as a Plant Growth Promoter and Biocontrol Agent against Fusarium Damping-off in Onion in Burkina Faso

This study is about an assessment of plant growth promoter and biocontrol properties of Trichoderma harzianum in onion. Two isolates of T. harzianum one originating from Eco-T (South Africa) and the other from a onion field soil (Burkina Faso) were evaluated for their use as onion growth promoters and their efficiency in protecting onion seedlings against damping-off caused by Fusarium oxysporum and F. solani. T. harzianum was used for coating onion seeds with a conidial suspension concentrated to 107 spores/ml and for directly spraying onion seedbeds with the same conidial suspension. Sowing was done with coated seeds in trays containing a doubly sterilized substrate inoculated or not with Fusarium strains. Non-coated seeds were sowed in the same substrate sprayed with T. harzianum conidial suspension and inoculated or not with Fusarium strains. All trays were kept in greenhouse for one month. Coating the seeds and spraying the seedbeds with the conidial suspension of the two T. harzianum isolates led to a significant increase in the number of living seedlings, seedling length, root length, number of leaves and fresh weight of seedlings 30 days after sowing in sterilized soils. Sowing the T. harzianum coated seeds in soils inoculated with Fusarium led to a significant reduction in seedling damping-off due to the pathogens and improved the growth parameters of seedlings compared with non-coated seeds. Spraying the conidial suspension of T. harzianum isolates on seedbeds inoculated with both Fusarium strains produced the same results, but at a lower intensity than was the case with seed coating. These results reveal that the use of an indigenous isolate of T. harzianum originated from Burkina Faso could be a novel biocontrol strategy against the damping-off of onion seeds in an environmentally sustainable way. This paper discusses further development of a simple and accessible method for the mass production and conservation of T. harzianum and the search for an effective and inexpensive sticker for seed coating. An isolate of T. harzianum native to Burkina Faso was shown to improve the germination of onion seeds and to protect seedlings against Fusarium damping-off. This isolate can be exploited in the development of integrated onion crop protection in West Africa

In vitro Evaluation of Antagonistic Activity of Trichoderma harzianum Pers. Isolates against Three Fungal Species Pathogens of Onion in Burkina Faso

L'action antagoniste de cinq isolats de Trichoderma harzianum Pers. dont quatre obtenus au Burkina Faso et un originaire de l'Afrique du Sud a été évaluée in vitro contre Aspergillus niger van Tieghem, Fusarium oxysporum f.sp.cepae Schlecht. Emend. Snyd & Hans et Fusarium solani (Mart.) Sacc. considérés comme les principaux agents pathogènes fongiques rencontrés sur l'oignon au Burkina Faso. Les espèces pathogènes et antagonistes ont été misezs en co-culture en confrontation directe dans des boites de Petri pendant 7 jours et les diamètres de croissance des pathogènes en présence ou non des antagonistes ont été relevés. Les deux isolats ayant présenté les plus forts taux d'antagonisme ont ensuite été mis en co-culture en confrontation à distance dans deux boites de Petri assemblées avec du parafilm et mis en culture. Tous les isolats de Trichoderma harzianum testés en confrontation directe ont inhibé la croissance in vitro des trois espèces pathogènes avec des coefficients d'antagonisme compris entre 0.61 et 0.93 et entre 0.01 et 0.24 en confrontation à distance. Les isolats ThTab du Burkina Faso et ThAfs de l'Afrique du Sud ont été les plus efficaces et ont exercé une action myco-parasitaire sur les trois espèces pahtogènes. Les modes d'action des antagonistes et les formes d'utilisation possibles en lutte biologique sont discutés