Tomato (Solanum lycopersicum L.) is one of the most important vegetables in Togo. Unfortunately, tomatoes are susceptible to many diseases, among which bacterial wilt caused by Ralstonia solanacearum causes major yield losses. In this study, incidence of bacterial wilt and its distribution was evaluated in the central region of Togo, the major tomato producing area in the country. Overall, 16 localities were surveyed in four prefectures. In each locality, three fields were visited, and the incidence of the disease was recorded, and diseased samples were collected for laboratory investigation. The results showed that bacterial wilt occurred in all the fields visited, indicating a field incidence of 100%, whereas the plant incidence ranged from 10.00±00% to 43.33±3.33%, with an average of 20.94±1.77%. The antibody based Immunostrip test was positive for R. solanacearum in 100% of the visited fields. From 144 samples collected from fields, 45 R. solanacearum isolates were isolated on Modified SMSA media. This survey results show that tomato bacterial wilt is a real threat to tomato production in the central region of Togo.

Tomato (Solanum lycopersicum), pepper (Capsicum annum), and gboma (Solanum macrocarpon) are major vegetables in Togo, with many people depending on these crops for their livelihood. In December 2018, during the dry season with temperatures between 21°C to 35°C, tomato (‘Petomech’), pepper (‘Gboyebesse’) and gboma (local landrace) showing wilt symptoms without foliar yellowing were collected from two locations, Tchouloum and CECO-AGRO sites in the Sotouboua Prefecture of Togo, ~300 km from the capital city of Lome. Disease incidence ranged between 10% to 50% in multiple fields. Cut stems of most wilting tomato, pepper and gboma plants produced bacterial ooze in water and vascular discoloration was visible in longitudinal stem sections. Ground cut stem tissue tested positive with Rs ImmunoStrips specific to the Ralstonia solanacearum species complex (RSSC) (Agdia Inc., Elkhart, IN, USA). Collected samples were stored at ambient temperature and cultured within 36 hr. Culturing sap from cut stems plated on modified SMSA medium (Engelbrecht 1994) yielded colonies with typical RSSC morphology: slow-growing, irregular, mucoid, and white with red centers. Genomic DNA was extracted from thirteen isolates: two from gboma, five from tomato and six from pepper. The expected 280-bp band was amplified from all 13 genomic DNAs following polymerase chain reaction (PCR) using the 759/760 RSSC-specific primer pair (Opina et al. 1997). PCR with the 630/631 primers, which identify the Race 3 biovar 2 RSSC subgroup, did not yield a product from any Togo isolate (Opina et al. 1997). The phylotype multiplex PCR identified all Togo isolates as belonging to the phylotype I subgroup, also called R. pseudosolanacearum (Prior et al. 2016; Fegan and Prior 2005). Phylotype control DNAs were from strains GMI1000 (phylotype I, Asia), K60 (phylotype II, Americas), CMR15 (phylotype III, Africa), and PSI07 (phylotype IV, Indondesia). Comparative genomic analysis of the partial endoglucanase (egl) gene, amplified with the Endo primer pairs (Poussier et al. 2000), revealed all Togo strains belonged to sequevar 17, a group known to cause bacterial wilt of peanut in China. (Xu et al. 2009). The egl sequences are in NCBI GenBank accessions MT572393 to MT572405. Koch’s postulates were completed by inoculating 28-day-old bacterial wilt-susceptible ‘Bonny Best’ tomato plants by soil soak (Khokhani et al. 2018). Briefly, soil around each unwounded plant was drenched with 50 ml of a 108 CFU/mL suspension of bacteria grown from a single colony. Five plants were inoculated with each of four randomly selected Togo strains. RSSC phylotype I strain GMI1000 served as a positive control and water treated plants as negative controls. Plants were kept in a 28°C growth chamber with a 12 hr photoperiod. All RSSC inoculated plants were fully wilted within a week; symptoms resembled to those observed in the field. Water treated control plants did not wilt. Culturing sap from all inoculated plants on SMSA medium yielded colonies with typical RSSC morphology that tested positive with the Rs ImmunoStrips. This is the first identification of RSSC in Togo. These results will guide development of disease management strategies and regionally appropriate breeding of vegetable lines with resistance to the phylotype I RSSC strains present in Togo.

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Tomato (Solanum lycopersicum L.) is of great socio-economic Tomato (Solanum lycopersicum L.) is of great socio-economic importance. Unfortunately, its production is limited in Togo by fungal diseases and bacterial wilt caused by Ralstonia solanacearum (Rs). The objectives of the study are to establish the status of major tomato diseases in Togo and control approaches used by the producers. The methodology led to a field survey allowing the evaluation of the incidence of fungal and bacterial diseases of tomato and the identification of their endogenous control methods. In the laboratory, the isolation and identification of the pathogens responsible for these diseases were carried out. The results show that the major diseases of tomato in Togo were, spots, organ decay and wilting plants. The incidence rate of fungal diseases ranges from 18.8% to 75% (fields) and from 0% to 15% (plants). The pathogens responsible are Sclerotium rolfsii (7.5%) Sclerotinia sclerotiorum (1.5%), Alternaria solani (2.5%) and Fusarium oxysporum (4.38%). The incidence rate of Rs wilt is 100% (field) and ranges from 10% to 43.33% (plant). The PCR test revealed that the bacterium responsible for tomato wilt in Togo is Rs belonging to phylotype I, Sequevar 17. Synthetic chemical pesticides are used to control these pathologies, which is a problem for human and animal health and environmental protection. Chemical pesticides have been identified, 60% of which are insecticides and 30% fungicides. The study revealed unproper practices in the management of pesticides in region covered by the research, leading to sanitary risks for farmers.

The effects of plant-based formulation on two common fungi of tomato were carried out in vitro. A total of five concentrations of the formulation: 0.2, 0.4, 0.6, 0.8 and 1% were tested using agar dilution and agar diffusion methods. Significant antifungal effects were observed. The plant-based extract formulation was more effective with the agar dilution method in comparison to the diffusion one and also depend on the higher concentrations. The antifungal effects decreased with the incubation time and a high effect was recorded after three days of incubation with mycelial growth inhibition from 63.60 to 77.76% and 80.08 to 100% for Alternaria solani, and from 47.72 to 74.83 and 78.8 to 100% for Fusarium oxysporum, with agar dilution and diffusion methods, respectively. Keywords: Tomato, collar fungi rot, plant extracts, Alternaria, Fusarium, control.