Our study aimed at assessing the effects of 3 Plants Growth Promoting Rhizobacteria (PGPR) either singly or in combination on maize growth under laboratory and greenhouse conditions. Seeds were inoculated with single and combined solution of 10⁸ CFU/ml of Rhizobacteria. Seeds were not inoculated for the control variant. The highest germination percentage was obtained with the combination of Pseudomonas fluorescens and Pseudomonas putida. This combination also recorded the best vigor index, plants circumferences number of leaves and the leaf area. The maximal heights of plants were observed with seeds treated with Azospirillum lipoferum with an increase of 37.32%. The highest rates of underground dry matter were recorded with A. lipoferum, with an increase of more than 56% comparative to control, while the combination P. fluorescens and P. putida increased the aerial dry matter of 59.11%. Finally, the highest value of the aerial biomass was obtained with the plants treated with the combination of P. fluorescens and P. putida and the highest underground biomass was obtained with plants treated only with A. lipoferum. These results s...

Spodoptera frugiperda has caused significant losses of farmer income in sub-Saharan countries since 2016. This study assessed farmers’ knowledge of S. frugiperda, their perceptions and management practices in Benin. Data were collected through a national survey of 1237 maize farmers. Ninety-one point eight percent of farmers recognized S. frugiperda damage, 78.9% of them were able to identify its larvae, and 93.9% of the maize fields were infested. According to farmers, the perceived yield losses amounted to 797.2 kg/ha of maize, representing 49% of the average maize yield commonly obtained by farmers. Chi-square tests revealed that the severity of the pest attacks was significantly associated with cropping practices and types of grown maize varieties. About 16% of farmers identified francolin (Francolinus bicalcaratus), village weaver (Ploceus cucullatus), and common wasp (Vespula vulgaris) as natural enemies and 5% of them identified yellow nutsedge, chan, shea tree, neem, tamarind, and soybean as repellent plants of S. frugiperda. Most farmers (91.4%) used synthetic pesticides and 1.9% of them used botanical pesticides, which they found more effective than synthetic pesticides. Significant relationships exist between farmers’ management practices, their knowledge, organization membership, and contact with research and extension services. More research is required to further understand the effectiveness of botanical pesticides made by farmers against S. frugiperda and to refine them for scaling-up.

Tel ; (+229)97123468 RESUME L'objectif de cette étude est de caractériser les rhizobactéries potentiellement promotrices de la croissance végétative ou encore en anglais « plant growth promoting rhizobacteria» (PGPR) vivant dans la rhizosphère de douze (12) différentes zones agroécologiques du sud-Bénin. Un échantillon composite de sol et de racines des plants de maïs est prélevé au niveau de 4 différents champs de producteurs par zone agroécologique. Des analyses agrochimiques et microbiologiques sont faites sur ces échantillons. Les résultats montrent que la flore totale des sols étudiés est riche en rhizobactéries. Quinze (15) espèces de PGPR différentes sont identifiées à de fortes concentrations dans tous les échantillons de sols et de racines. Il s'agit de trois espèces de Pseudomonas, trois espèces de Streptomyces, huit espèces de Bacillus et une espèce de Azospirillium. Les sols du sud-Bénin contiennent naturellement des rhizobactéries potentiellement promotrices de croissance végétative. Il ne se dégage pas de lien entre les propriétés chimiques des sols des différentes zones d'étude et la distribution des rhizobactéries PGPR.

Effets des rhizobactéries PGPR sur le rendement et les teneurs en macroéléments du maïs sur sol ferralitique non dégradé au Sud-Bénin

The survival of Xanthomonas axonopodis pv. vignicola, incitant of cowpea bacterial blight and pustule, in residues of infested cowpea leaves was studied in the field in the forest savanna transition zone of South Benin and under variable controlled conditions. The pathogen survived for up to 60 days when placed on the soil surface, and up to 45 days buried at depths of 10 and 20 cm. In the glasshouse, bacteria survived in residue mixed with soil for at least 2 months in dry soil and less than 2 months in moist soil. The pathogen survived at least 30 days in the field after spray-inoculation on the weed species Euphorbia heterophylla, Digitaria horizontalis and Synedrella nodiflora; 20 days on Panicum subalbidum; 10 days on Euphorbia hirta; and 5 days on Talinum triangulare. After leafinfiltration under glasshouse conditions, the pathogen was detected after 90 days in D. horizontalis; 75 days in T. triangulare, P. subalbidum and S. nodiflora; 60 days in E. hirta, and 30 days in E. heterophylla. Among 12 legume species tested as alternative hosts of X. axonopodis pv. vignicola, only Sphenostylis stenocarpa (African yam bean) showed typical symptoms of cowpea bacterial blight in a glasshouse experiment following artificial inoculation. This is the first time this legume species has been identified as a potential host of X. axonopodis pv. vignicola. Crop residue and weeds are likely sources of primary inoculum when planting two consecutive cowpea crops per year and they probably play a role in dissemination of the pathogen during the cropping season. The alternate host may form a bridge for primary inoculum between cropping seasons.

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In June 2004, wilted tomatoes with no foliar yellowing were observed in Ouègbo, Atlantique District, Benin. The cut tomato stems released whitish bacterial ooze. Longitudinal sections of most stems showed brown vascular discoloration. Twenty symptomatic tomato plants were collected from 10 fields and exported to the Institute of Plant Disease and Plant Protection, Leibniz Universität Hannover, Germany. Bacteria were isolated on triphenyl tetrazolium chloride (TTC) medium (2) and three of the nine bacterial isolates that resembled Ralstonia solanacearum (colonies with red center and whitish periphery) and reference strain ToUdk (race 1 biovar 3; N. Thaveechai, Kasetsart University, Bangkok, Thailand) were used for pathogenicity tests. Five 4-week-old tomato plants cv. Tohounvi, grown in individual plastic pots (14 × 16 cm) containing sterilized field soil, were inoculated with each of the four isolates individually by soil drenching with 30 ml of the test cultures at 108 CFU/ml. Control plants were treated with 30 ml of sterile water. All plants were incubated in a glasshouse at 30°C. All plants inoculated with the isolates from Benin wilted 4 days after inoculation with symptoms similar to those observed in the field. Plants inoculated with the reference strain wilted 7 to 11 days after inoculation. Control plants treated with water remained healthy. R. solanacearum was recovered from the 20 symptomatic plants on TTC medium. The identity of the strains in comparison with the reference strain was confirmed by PCR with species-specific primers 759/760, which produced a single 281-bp fragment (3). Because similar symptoms were being increasingly reported by farmers across Benin and linked with reduced tomato yields, a disease survey was undertaken by IITA in 2006 and 2007. Wilted tomato plants were found across all agro-ecological zones of Benin (3 to 72% of plants per field). Isolates were recovered from the southeastern districts of Adja-Ouèrè, Sakété, Adjohoun, and Dangbo, the southwestern districts of Klouékanmè and Athiémé, the southern districts of Toffo and Bohicon, the central districts of Dassa and Savè, and the northern districts of Malanville and Karimama. Identification of R. solanacearum was confirmed following inoculation of tomato, production of characteristic wilting symptoms, recovery of the pathogen on TTC medium, and positive identification with ELISA kits (Pathoscreen Rs; Agdia Inc., Elkhart, IN). To our knowledge, this is the first report of R. solanacearum infecting tomato in Benin. Tomato is the most cultivated vegetable crop in Benin and important to the livelihood of many people in peri-urban and rural areas. Understanding that the cause of the observed crop losses is R. solanacearum may lead to implementation of management strategies such as deployment of disease-resistant cultivars or grafting tomatoes onto bacterial wilt-resistant rootstocks (1). References: (1) P. Aggarwal et al. Indian J. Agric. Sci. 78:379, 2008. (2) A. Kelman. Phytopathology 44:693, 1954. (3) N. Opina et al. Asian Pac. J. Mol. Biol. Biotechnol. 5:19, 1997.

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